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AMOS AlphaPascal

1. 3 2 B 8 9 5 EXTENSION ww 10 19 EXTERNAL u a a we waw wu 33 6 12 16 1 External declaration a a a a 6 12 External Library a s eas s s a 2 2 Br 4 1 6 12 16 1 Modifying 6 we 5o 6 5 Version number a s s s a sawa 4 18 16 5 Version stamp s s a a e a 4 18 FACTORIAL a 1 FALSE an 7 lanka a pre a ge Sh wt i SOU ws le he E LEIS T 15 ALPHA PASCAL USER S MANUAL Page Indexr4 File error codes a e 14 14 tite Handling naco aata Eb File locks a File search pattern s a a a e s 4 5 File specification a s a 310 16 File window s ma 3 File identifier s e a e a FILESIZE 5 202 6 ie rr T0280 PILECHAR a e Wa an a A Floating point numbers a e e 975 FOR DO Xu ou xw Formal parameters a s a s a s a 6 11 Formatting output e s a 10 10 FORWARD a a Forward declaration s s s s a 6 10 ESPEC paa a ve ee a a MA 10s21 FUNCTION 1 470 a anad a 1553 Function block s uno Funetron call 2 22 4 8 1 Function declaration s a s a 6 6 Function result s soe x e 5 76 GEF bn ca xb s ss GETFILE ma wow GETLOCKS s BOTO 5 V Sade xut fer ef a Heading aa an uw a a 5 1 H aD cmr Ban x wy oUm A o IAS L O errors mai 3 1 Identifier a a s n n 5 2 Identifier scope a a 2 2 TESTHEN vec a aaa ouo ORG 9 5 1 4 7 EF i ui IF THEN ELSE
2. DATA TYPES Page 7 15 PROGRAM VAR Y1 Y2 Y3 NT1 N2 N3 CHAR Query CHAR Yes No SET OF CHAR BEGIN eT Yes 5 Y No C n WRITELNC The only valid response to a Yes No question is Y or N WRITELNC We Ll Let you add your own answers WRITELN WRITELN Enter three one character symbols that can stand for YES ab WRITE separate them with a space not a comma READLN CY1 Y2 Y3 Yes Y1 Y2 Y31 Yes Add user defined symbols to Yes WRITEC Now enter three symbols for NO Dz READLN N1 N2 N3 2 No i N1 N2 N3 No Add user defined symbols to No gt WRITELN WRITEC Let s test this out Enter a Yes or No answer READLN Query WRITELN e e IF Query IN Yes THEN WRITELNC Yes ELSE TF Query IN No THEN WRITELN No ELSE WRITELNC T didn t understand you END 7 2 6 FILE A file is a structured data type that contains a sequence of elements of the same type Since you can only access one element at a time files might seem much like an array The important difference is that file are associated with AMOS disk files and so can store data permanently beween program runs Files are the means of communicating with devices such as terminals and printers In addition unlike other structured types the size of a file does not have to be declared and may be of any size supported by the AMOS file structure Files typically hold data of type CHAR or they contain records see Sectio
3. Equality Scalar STRING SET or pointer operands BOOLEAN result lt gt Inequality Scalar STRING SET or pointer operands BOOLEAN result lt Less than Scalar or STRING operands BOOLEAN result gt Greater than Scalar or STRING operands BOOLEAN result lt Less than or Scalar or STRING operands BOOLEAN result equal Cor set SET operands BOOLEAN resulta inclusion subset Greater than Scalar or STRING operands BOOLEAN result or equat Cor set SET operands BOOLEAN result inclusion superset IN Set First operand is any scalar second is its membership SET type BOOLEAN result 8 1 5 Logical Operators NOT Negation BOOLEAN operands BOOLEAN resuit AND Conjunction BOOLEAN operands BOOLEAN result OR Disjunction BOOLEAN operands BOOLEAN result EXPRESSIONS Page 8 7 8 1 6 Set Operators Union Given sets of type X result is of type Xa Set difference Given sets of type X result is of l type X Intersection Given sets of type X result is of type X 8 2 CONSTANTS A constant is a value that doesn t change For example the number 34 5 is a constant because it can assume no other value Certain constants have been pre defined by Pascal for your use They are MAXINT the maximum integer AlphaPascal can represent FALSE Boolean false TRUE Boolean true You can use these constants as you would any others For example Find the minimum of a list of numbers Initialize CurrentM
4. Let s look at an example of a function and function invocation Suppose your program frequently needs to check the range of input numbers A simple function to make sure that a number is between 1 and 100 might Look something Like this PROGRAM Validate Validate a numeric entry make sure that it is between 1 and 100 VAR Target REAL FUNCTION ErrCheck Local REAL BOOLEAN Function does error checking on entry If 100 lt number lt 1 ErrCheck reports error by returning a TRUE gt BEGIN Begin function ErrCheck gt ErrCheck Local lt 1 OR Local gt 100 END End function ErrCheck BEGIN Main Program WRITEC Enter a number between 1 and 100 READLN Target IF ERRCHECK Target THEN WRITELN Invalid entry try again ELSE WRITELN C Very good Correct entry END Main Program 3 Note that until the program begins executing the main program where the function is actually invoked the function is not executed even though the function definition appears at the front of the program 6 6 2 Procedures The major purpose of a function is to compute and return a value The main purpose of a procedure is to perform a Set of operations For example let s say that you are designing a program that plays a card game At various times throughout the program you may need to simulate the shuffling of a deck of cards Rather than include this same piece of code throughout your program which would
5. EXPRESSIONS The modifying assignment operators are Adding modifying assignment operator es Subtracting modifying assignment operator Multiplying modifying assignment operator 7 Dividing modifying assignment operator As another example the statements Number 1 FOR I 1 TO 5 DO Number 2 Same compute two to the fifth power and 32 8 1 3 Arithmetic Operators The arithmetic operators are lunary Identity unary 3 Sign inversion Addition Subtraction Multi plication DIV Integer division Real division MOD Modulus as Number Number 2 So Number takes on the values 2 4 8 16 Takes INTEGER or REAL operands result is same type as operands Takes INTEGER or REAL operands result is same type as operands Takes INTEGER or REAL operands result is same type as operands Takes INTEGER or REAL operands result is same type as operands Takes INTEGER or REAL operands result is same type as operands Takes INTEGER operands result is INTEGER Takes INTEGER or REAL operands result is INGEGER or REAL Takes INTEGER operands result is INTEGER NOTE If you wish to use the sign inversion symbol you must enclose the number in parentheses if another the expression 3 5 is illegal 0932 is valid and evaluates to 15 operator precedes the number For example but the expression EXPRESSIONS Page 8 6 8 1 4 Relational Operators
6. WRITING AND MODIFYING AN EXTERNAL LIBRARY Page 16 2 To allow programs to be written which can serve either directly as a program or indirectly as a library a special BOOLEAN function is provided called MAINPROG which takes no arguments and returns true if the program in which it is executing is being used as the main program and false if the program in which it is executing is being used as a Library to another program The idea is to write a program in such a way that if it is being used as a library all it does is initialize global variables 16 1 STDLIB STDLIB is a special library which itself has no library t provides a basic set of mandatory procedure and function definitions it is permissable for you to overide any of these definitions with your own external procedures or functions with the exception of RDC RDI ROR RPS REN WLN WRB WRC WRI WRR and WRS Calls to these procedures are automatically generated whenever you use READ and WRITE statements READ and WRITE will seriously malfunction if you redefine any of these The functions and procedures included in STDLIB are ARCCOS Arc cosine function ARCCOSH Hyperbolic arc cosine function ARCSIN Arc sine function ARCS INH Hyperbolic arc sine function ARCTAN Arc tangent function ARCTANH Hyperbolic arc tangent function CONCAT Function to cencatenate strings COPY Function to copy ch racters in string COS Cosine function COSH Hyperbolic cosine function
7. E J OF ARRAYE1 5 OF INTEGER Pascal also allows a shorthand form TYPE InvoiceNums ARRAYL A E 1 51 OF INTEGER The statements above create a two dimensional array of 25 elements Each element is referenced by a pair of subscripts If we wanted to make a pictorial representation of our array InvoiceNums it might Look something Like this with the Xs representing integer numbers contained in the array KE 2 wo E 3 A XxX x x x X B Xx X X X X Co x x x 023 X Do X xX X X x E Xx X X x X If we wanted to access any number in the array we would have to specify the subscripts that designate the proper location In the example above A LL E designate array rows 1 5 designate array columns The subscripts for a two dimensional array must identify the element s row and column For example to identify the element marked with a question mark in the table above we would ask for Row C Column 4 InvoiceNumsL C 41 The number of dimensions an array may contain is Limited only by the room in memory 7 2 5 STRING We have already mentioned the data type CHAR A variable of type CHAR contains a single ASCII character However we often need to refer to collections of characters such as words names or addresses rather than just single characters DATA TYPES Page 7 11 The standard data type STRING allows you to declare variables that contain a group or string of ASCII characters For examples VAR AccountID
8. First THEN WRITELN Correct The value returned by PRED is not a variable or an expression therefore trying to use WRITE or WRITELN to display that value causes an error That is you may not say WRITELN PRED Second 2 PROGRAM TestPred TYPE Daysoftheweek Mon Tue Wed Thu Fri VAR Day Daysoftheweek BEGIN TestPred Day Tue IF PRED Day Mon THEN WRITELN Today is Tuesday Day z PRED Day IF Day Mon THEN WRITELN It s Blue Monday END i TestPred 3 Changed 30 April 1981 MISCELLANEOUS FUNCTIONS AND PROCEDURES Page 11 5 When you run the program above it prints Today is Tuesday It s Blue Monday 11 1 7 RELEASE The RELEASE procedure is used with MARK and NEW to use dvnamic variables with a stack like structure called the heap See Section 11 1 5 MARK for information on the heap It de allocates the dynamic Variable at the specified heap location The RELEASE invocation takes the form RELEASE variable identifier where variable identifier is the same argument as that supplied to MARK For example if you use MARK to get the current state of the heap use NEW to aliocate a dynamic variable which advances the top of the heap past the value returned by the previous MARK and then use RELEASE with the value returned by the previous MARK RELEASE de allocates the dynamic variable from the heap A picture might help to clarify Procedure The Heap NEW VD YO M
9. DELETE Source Position 3 9 WRITELN Source END TestDelete gt The program above prints the string Now 3s the time for all STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 4 13 1 4 INSERT The INSERT procedure inserts the specified string into a specified destination string It begins the insertion at the specified position in the destination string The invocation of this procedure takes the form INSERT CInsert string Dest ination string Index where Destination string must be a string variable for example PROGRAM TestInsert VAR Insertion Destination STRING BEGIN TestInsert 3 Destination Customer name is Insertion Robert Allen INSERT CInsertion Destination 19 WRITELN Destination END Testinsert gt The program above prints Customer name is Robert Allen 13 1 5 LES The LCS procedure converts upper case characters to lower case The procedure invocation takes this form LCS SourceString where SourceString is the string to be converted For example PROGRAM TestLCS VAR CustomerID STRINGE22 BEGIN TestLCS CustomerID Alfred J Prufrock Jr LCSCCustomeriDO WRITELN C Converted name is CustomerlID END TestLCS D The program above prints Converted name is alfred j prufrock jr STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 5 13 1 6 LENGTH The LENGTH function returns the number of strin
10. SOFTWARE MANUAL AlphaPASCAL USER S GUIDE DV M 00100 08 REV BO1 Ce HR ALPHA PASCAL USER S MANUAL Page 11 NOTE This printing of the manual contains the contents of Change Page Packet 1 for the ALphaPASCAL p 8 10000 100 which Micro Al User s Manual may be ordered separately from Alpha First Printing 1 August 1980 Second Printing 30 April 1981 Alpha Micro AMOS ALphaBASTC AM 100 AlphaPASCAL AlphaL ISP and AlphaSERV are trademarks of ALPHA MICROSYSTEMS Irvine CA 92714 This book reflects ALphaPASCAL Versions 2 0 and Later 7981 ALPHA MICROSYSTEMS ALPHA MICROSYSTEMS 17881 Sky Park North Irvine CA 92714 C 2M 10 81 ALPHA PASCAL USER S MANUAL Table of Contents aage orap seem xa 5 om oe nawa naaa esee soso a hoo pana Desa ES Koro ses CHAPTER 1 INTRODUCTION 1 1 ORGANIZATION OF THIS BOOK o onoonscnananaso 1 2 PASCAL BIBLIOGRAPHY soonnrososonananasanas 1 32 GRAPHICS CONVENTIONS USED IN THIS BOOK CHAPTER 2 GETTING STARTED Pal WHAT CES BASCALUT ing ii ma M m oe Qus SAMPLE PROGRAM dera ns al eleva aes 2 3 BRIEF DEMONSTRATION oooocnnonnanananasso e 2 3 1 Building a Pascal Program senono on 2 5 1 1 The VUE Text Editor 2 3 2 Compiling and Linking a Pascal Program ennanananeannannan 202 3 Running a Pascal Program umasasssos PART I THE ALPHA PASCAL SYSTEM CHAPTER 3 COMPATIB
11. STRING The default maximum string length is 80 characters but you can set the string length maximum to from 1 to 255 characters To set maximum string Length follow the identifier STRING with an integer constant in square brackets For example TYPE OrderIb STRING 253 The STRING data type is approximately equivalent to TYPE STRINGINI PACKED RECORD LEN 0 255 TXT ARRAY 1 N OF CHAR END ud if N above is omitted STRING defaults to size 80 NOTE The structure given above for STRING is approximate and is only given for illustrative purposes you cannot access the length of string X by referring to X LEN The computer stores strings with one character per byte and one byte at the front of the string which telis Pascal how long the string is Pato TEXT The standard data type TEXT is equivalent to the type FILE OF CHAR For example suppose you want to declare and open a text file you could say PROGRAM ReadListing TYPE ListFile TEXT VAR ProgramList ListFile BEGIN ReadListing gt OPEN CProgramList ACCNTT DAT OUTPUTO read data from file gt END ReadListing 3 NOTE In the example above it would also have been valid just to say VAR ProgramList TEXT Note to users of previous versions of AiphaPascal the file type INTERACTIVE is no longer needed or supported Replace any occurrences of the identifier INTERACTIVE with TEXT or at the front of your program re define INTE
12. is called a ilocal GENERAL INFORMATION Page 5 8 _ K _ Main Program BlockA BlockB BlockB1 y BlockA1 BlockA2 BlockB2 o Figure 5 1 Nested Structure of Program Blocks Let s say that a constant is defined both in the main program and BlockA BlockA itself and the blocks enclosed in BlockA Block41 and BlockAd use the definition made in BlockA The main program BlockB Block B1 and BlockB2 use the constant definition made in the main program The following small program demonstrates identifier scoping The variable Counter is declared both within the main program and within the procedure InnerBlock Changed 30 April 1981 GENERAL INFORMATION Page 5 9 PROGRAM Scope This program tests identifier scoping 3 VAR Counter INTEGER t Counter declared for main program PROCEDURE InnerBlock VAR Counter INTEGER t Counter declared for Procedure InnerBlock gt BEGIN i Counter 1 FOR Counter 1 TO 10 po BEGIN HE WRITELN Procedure InnerBlock Counter Counter END END f End Procedure InnerBlock Y BEGIN Main Program Counter z 20 WRITELN Main Program Counter Counter InnerBlock Invoke Procedure InnerBlock WRITELN C Main Program again Counter Counter END End Main Program 3 If our description of identifier scoping is correct we would expect the statement WRITELNC Main Program ag
13. o e a 15 2 Data structures a e e a 2 2 ALPHA PASCAL USER S MANUAL Data type uu s esa s ea a a Hk 7 1 Debugging s wim Decimal notation s s a s e 5 10 Declarations a a a a e a a n 61 Declaring Page Index 3 Functions a 6 s ea a s as o 676 Labels o aww d a a oa u r 6 2 Procedures w eae suwan a o 679 TYVDG e Ge aow w a E beh Variables s a ao o a a v 671 6 6 Declaring external elements 6 12 Declaring variables s s uno f2 Defining constants s e s a e s Be DELETE x a a Disk blocks s Displaying file locks ea Dynamic variables s oce rece e Sl 13G E SYMbO Lk ute fe Sow ver gad END a X wo a wow ee ds 542 554 End of file s a a a s s e n a a a 103 10 16 End of line a e e s e a os a 10 4 a5 e wo BAO End of line separators a e ca 19 15 EOF e my el oe an om Seem TORS TOS TS EOLN eu loh ce moo x NOU osse P ow o 104 L ERASE 2 ee ee te ee 10 19 ERROR wow RR a ra Balle woes 14 10 Error codes WO coe we a T S Error handling aoa 14 12 15 5 ERRORINFO a a a a a a 14 13 EXIT o ms x wo SS 999 14 15 EXP moie we Be ley om ge Sb Ec erm wc RAS EXPONENT ma 2 a o 5 124 Expression a a 8 1 Expression handling a e 5 2 Expressions Assignment operator s a 322 CASE OF construct n e mana 92 9 6 IF THEN ELSE construct
14. scanning Only formal VAR FILE parameters are permitted C expected assumed missing Function must be of scalar subrange or pointer type Changed 30 April 1981 ALPHA PASCAL USER S MANUAL G compiler options SI compiler option a a L compiler options SP compiler option a SQ compiler options R compiler options INC files maa JPCF files sae wun PO files a nyo PSB files ILINK Linker option SMASH Linker option Qu Aborting command file execution ABS uox ox cw wo A Actual parameters AlphaBASIC file locks AMOS file specification AMOS files as AND s a vu ARCCOS a un nu ARCCOSH oo ARCSIN a wa ARCSINH wan ARCTAN ao a 0 ARCTANH a a 7 4 Arithmetic operator a a ARRAY 4 e sow a Array index au ASC ED woo ode wey See ASCII character set ASCII value n a a s Assembly Language subroutines Assignment operator a Assignment statement BEGIN a Vol woxocw x Bibliography a s s a gt Block m ww 0 qu Block structure s Blocking records a a LI Index ben hr 4 8 4 10 4 10 4 10 6 2 4 11 4 5 11 k 13 15 1 4 15 15 2 15 5 4 16 4 19 7 15 10 14 Page Index 1 ALPHA PASCAL USER S MANUAL Page Index BOOLEAN a s a s a so a e a o 7 83 15 4 Buffer variable s a a a 1 CASE expressions s a a s o es s
15. while other procedures generate an error if the file doesn t exist doing a LOOKUP before one of these procedures is a good idea For example PROGRAM LookForit VAR FileID FILE OF CHAR Target STRING Query CHAR X INTEGER BEGIN LookForlt 3 WRITE Enter the file you want to write to READLN Target X 285 FSPECCFileID Target DAT IF LOOKUPCFiLeID THEN BEGIN WRITE That file already exists Destroy it Y or Nd READLN Query IF Query N THEN EXIT PROGRAM ERASE FileID WRITELN File erased END OPENO CFiLeIDO WRITELNC File Target opened for output END LookForIt 3 The program above checks to see if the file specified by the user already exists If the file exists the user is asked to decide whether or not to save the file or get rid of it and start a new one of that name INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 25 10 2 12 OPEN The OPEN procedure opens a sequential file for input or output or opens a random fite for both input and output The invocation takes the form OPEN file identifier filespec mode where file identifier is a file variable and filespec is a valid AMOS file specification Mode may be INPUT OUTPUT or RANDOM and specifies whether the file is to be a sequential file used for input or output or in the case of RANDOM whether it is to be a random file used for input and output both If you are using OPEN in OUTPUT mode it d
16. 4 X AND Y gives a result of TRUE if both X and Y are TRUE or FALSE if either X or Y or both are FALSE When we use the relational operators on INTEGER REAL CHAR or STRING data types the result is always of type BOOLEAN You may use the PRED and SUCC functions on data of type BOOLEAN and you may use the set membership operator IN You may also use the ORD function ORDCFALSE 0 ORDCTRUE 1 Fetah CHAR The computer recognizes a specific set of characters that it can represent The elements of this set are ordered for example A lt B lt C In the case of the Alpha Micro computer this ordering is called the ASCII collating sequence and the set of characters is called the ASCII character set For a List of the ASCII characters see Appendix B The ASCII Character Set A CHAR variable contains one ASCII character To indicate an element of CHAR data type enclose it in single quotes For example VAR MenuChoice CHAR MenuChoice Af The relational operators have been defined for use on CHAR data Remember that A lt B because of their position in the ASCII collating sequence You may also use the set membership operator IN on data of type CHAR To designate data as type CHAR use the CHAR standard identifier VAR Initial CHAR or TYPE Character CHAR VAR Item Character Because CHAR is a non REAL scalar type you can use the SUCC and PRED functions to identify predeces
17. A 5 1 2 Scalar Data Types sanan ATE A 3 2 Structured Data Types oononooma wa Ark Ak Sagat Strinq 224 A a aia eed ASD A 5 2 2 APPAYS seuncaunes A A 5 A 5 2 5 SETS A o ASS A 35 2 4 File Type oooo oo www eas AO A 5 2 5 Record Type cooooonnnanans DS A 5 2 6 Pointer Data Types nonnono O T A 4 EXPRESSIONS Jaweunccounenannnn aan Panaad a OO A amp 1 Operators OA aaa Cn RBA ASSIGNMENT suesnoanssanasasnaae A 6 A 4 1 1 1 The Modifying Assignment Operators oonn 4 7 A 4 1 2 Arithmetic Operators Av A 4 1 5 Relational Operators ooo na An A 4 1 4 Logical Operators sa An A 4 1 5 Set Operators sonsooscnsonasss An A 4 2 COnstants SN M RN EARS E MEA vie es ATS A 4 5 Variables T nas ArB A 4 4 Function Calls sasaaa AR PAP ets dass APS A 4 5 TF THEN ELSE and CASE OF Constructs in Expressions a EN A A 9 Aad STATEMENTS zcuaaza the uis cw wid ar ey a Gees BIR oa mime eee as A9 A 5 1 Simple Statements iaaeuwnnuenwenunan sae A9 A 5 1 1 Assignment Statement A 9 A 5 1 2 Procedure Call sssaasausanszaas AWG A 5 1 3 GOTO Statement TEE AO A 5 1 4 Null Statement n n ne ATO 4 5 2 Structured Statements a oonaoon ooon nee 4 10 A 5 2 1 Compound Statements saena vex ATO A 5 2 2 Conditional Statements A 10 A 5 2 5 Repetitive Statements wa A711 A 5 2 4 WITH DO Statements ronnoaoanoro Ant A 6 ALPHA PASCAL STANDARD FU
18. AMOS command Level enter PRUN followed by the specification of the file that contains the program you want to execute Then type a RETURN For example PRUN LSTSQRC200 13 4 5 1 Library Version Checking Because you can add routines to the external Library the situation can arise where an old program was Linked with an external Library that is different from the current external Library PRUN will not execute a program that is not compatible with the Library it is being run with By compatible we mean that a program that was linked with a certain external library cannot be run with an older version of that Library or with a completely different library OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 18 You will rarely have to worry about Library version numbers if you modify a Library you can run programs Linked with earlier versions of that Library without re Linking the programs unless you changed functions and procedures used by those programs in which case you might have to change your programs to be compatible with the new procedures and functions AlphaPascal uses a system of version numbers and version stamps to keep track of program and Library versions These numbers are for internal use only they are not accessible to your programs Whenever a library is created or modified AlphaPascal writes a unique identifying number called the version stamp to that Library It also keeps track of the number of version stamps
19. DELETE Procedure to delete characters in string ERRORTRAP Default error handler EXP Function to compute e to the specified power FACTORIAL Factorial function x GETFILE Procedure to get information in filespec GETLOCKS Procedure to read file Locks INCHARMODE Returns true if terminal is in Charmode INSERT Procedure to insert characters into a string KILCMD Procedure to abort command file LCS Function to convert upper case characters to lower case LN Function to compute natural Napierian log LOG Function to compute log base ten of argument OPEN Procedure to open an AMOS file POS Function to compute position of character in string POWER POWER x y computes x to the y th power PROGRAM STDLIB initialization PWROFTWO Funetion to compute powers of two RDC Routine used by READ RDI Routine used by READ RDR Routine used by READ RDS Routine used by READ WRITING AND MODIFYING AN EXTERNAL LIBRARY Page 16 3 ia l RESET Procedure to close a file and then open for input REWRITE Procedure to close erase and then open a file for output RLN Routine used by READ SETFILE Procedure to place file information in filespec SIN Sine function S INH Hyperbolic sine function SPL Routine used by SPOOL must not be called directly SPOOL Procedure to spool files to Line printer STDERRORTRAP Standard error handler STRIP Procedure to strip trailing blanks from string SQRT Square root function TAN Tangent function TANH Hyperbolic tangent function
20. ERRFIB TEXT sea Additional information for internal use only END EXTERNAL PROCEDURE XERRORTRAP VAR INFO INFOREC EXTERNAL PROCEDURE STDERRORTRAP 14 10 2 ERRORTRAP To catch errors you must write a global procedure of no arguments with the name ERRORTRAP Here is a very simple example of such a procedure SYSTEMS FUNCTIONS AND PROCEDURES Page 14 13 O PROCEDURE ERRORTRAP BEGIN 3 STDERRORTRAP END In this example we simply call the standard system error handler STDERRORTRAP In order to determine the nature of the error which has Tnvoked errortrap you must use the function ERROR INFO in conjunction with a variable declared as type INFOREC PROCEDURE ERRORTRAP AR INFOP INFOREC BEGIN INFOP ERRORINFO WRITELN Error INFOP XEQERR STDERRORTRAP END In this example we also display the error code corresponding to the error which occurred before calling the standard error handler The List of error codes is as follows Error Code Meaning qu 1 Value range error 3 Exit from uncalled procedure 4 Memory capacity exceeded 5 Integer overflow 6 Divide by zero 7 Bad pointer reference 8 Control e 10 1 0 error 41 Unimplemented runtime instruction 12 Floating point error 13 String overflow 14 Programmed HALT 15 Programmed breakpoint 16 ARCSINOO or ARCCOS x where abs x gt 1 17 LOGOO or LNOO where x lt O 18 SARTOO where x lt 0 19 TANCPI 2 k PI is undefined for inte
21. IF CA B AND C D THEN See Section 8 1 1 Operators for information on operator precedence gt Two new keywords have been added to the List of reserved words EXTERNAL and MODULE In addition several identifiers have been added to the standard identifier List For a List of AlphaPascal standard identifiers see Section 5 4 2 Standard Identifiers Also several standard identifiers used by standard Pascal are NOT used by AiphaPascal DISPOSE PACK and UNPACK since AlphaPascal does not use these procedures AlphaPascal uses MARK and RELEASE to reclaim memory allocated by NEW and automatically unpacks packed data Structures for you when necessary See Section 11 1 4 NEW for information on allocating dynamic variables Standard Pascal supports the data type CHAR single character AlphaPascal also supports a non standard type STRING which contains a Length field as well as a field of characters See Section 7 2 3 STRING for a description of this data type COMPATIBILITY AND CONVERSION Page 3 7 3 3 MAKING PROGRAMS COMPATIBLE WITH THE NEW ALPHA PASCAL In general programs written in previous versions of AlphaPascal or standard Pascal will require very little modification before being runnable under the current AlphaPascal For example the sample program given in Chapter 2 runs correctly in any of these versions of Pascal The largest number af changes will probably involve functions and proce
22. Parameters a a Pascal L S ela des Sem ces Ue PEDO ous Haba a 4220 POLLDOS Le xS uu a ici xs PCU DO 4 o4 ex a ooo woo GZ PRIEE Q0 l2 Xxx ox a x c9 uw T026 PE DOs n were uec o wx s won DEDI UU e COMETE PLENKC ay Nai naw ues once vw ae GV a HEPES a PoYDteP s e wecw x 0e AO tO 7220 19 44 Pointer data type a s a a n e 7 19 POS eia la ue ise qur ell oan use tas USD PD D TRE 159 POWER S a sa na sm dw ww e vw a NARA Pre declared constants a s a 8 7 PRED amp 4 409 o xo mw wow 272p 7 S8 TEL Previous versions of AlphaPascal 71 Printer queue a a s n a 143 Procedure uiu aeo cas 573 Procedure call a a eo 91 Procedure declaration a e PROGRAM 4 m c scr w IU om UR Program declaration Program LUSTING 4 4o 4o 9x cx Program name Program structure s a no una Prohibiting BOTOS ormoc PU DO 2g ue oV ow BA VoU a da PUT sreca oou Ae ee le up Roc UN sie PWROFTEN pa dw cR UE Sok des Rss PWR FTWO Low os AL eoe 8 I i i j Pur d VAR VUL i to 10 6 A SR fun OS RIM 4 Quiet compiler display a s a 4 10 RADSO pa o a sa 10 26 Random files s a e s a 10 15 RANDOMIZE o amp w aa s 9o ow o x o 1e 5 Range checking a a non a 4710 READ y ae aa Wow ox cw DOTT READLN xvm Mer de oo3 a cmo m ces TORS REAL WG 4e Ge ak sw sa 03 4554 Real
23. Pascal evaluates the expression 312 34 20 as 312 34 20 EXPRESSIONS Page 8 2 evaluating the value 312 34 first and then subtracting 20 from it If the precedence of the operators differs Pascal evaluates the elements connected by the operator of highest precedence first and then evaluates the elements connected by the operator of the next highest precedence and so on For example multiplication has a higher precedence than addition so the expression T6 54 2 tells Pascal to multiply 76 by 54 and then add 2 to that value The expression evaluates to 76 54 2 or 4106 You can change the order in which Pascal processes operators by using parentheses Pascal always evaluates elements in the innermost set of parentheses first and then works outward For example if you want Pascal to act upon the addition operator first in the previous example you must use parentheses to tell Pascal to apply that operator first T6 54 2 This expression tells Pascal to add 54 and 2 and then multiply that value by 76 The expression thus evaluates to 4256 NOTE The operator precedence used by AlphaPascal differs slightly from that used by standard Pascal We have changed the precedence to be compatible with that of other Language processors on the Alpha Micra system Specifically in AlphaPascal the Boolean operators are of lower precedence than the relational operators The only time you will need to worry ab
24. even when called from an inner procedure Begin at the caller of the procedure which set X to ERRORINFO 14 10 4 ERROR The procedure ERROR x takes an INTEGER x as argument and generates the corresponding system error See the previous section for the list of error codes changed 30 April 1981 SYSTEMS FUNCTIONS AND PROCEDURES Page 14 15 exception of a Control C followed by a command to resume Thus the ERRORTRAP procedures themselves have aborted to AMOS in most circumstances In addition STDERRORTRAP resets INFOP XEQERR to zero before returning if execution is to be resumed This is because errors MUST NOT occur in the error handler itself for obvious reasons AlphaPascal assumes it is executing an error handler whenever XEGERR is nonzero If an occur does occur within an error handler the message Attempt to cali ERRORTRAP while in ERRORTRAP is displayed a direct abort to AMOS is made without closing any open files Thus by reseting XEQERR to zero STDERRORTRAP signals to AlphaPascal that error handling is finished and further errors are again acceptable Should you decide not to call STDERRORTRAP at all please keep in mind the following points 1 The only errors from which you may safely resume execution are amp a Control C and 10 1 0 error An attempt to resume execution by returning from ERRORTRAP with any other errors will probably crash the system 2 It is acceptable to use EXIT to abort some fu
25. must always mount a disk after you have changed it and before you write to Tt Otherwise the system will think that the old disk is still in the drive and use the old disk s bitmap to find unused disk blocks 14 7 1 Error Codes The error codes returned by XMOUNT are specified in a TYPE declaration at the beginning of program having provided the form TYPE MOUNTERROR MOUNTED UNMOUNTED DEVNOTFOUND BADHASH NOVOLIDO Next some variables will have to be defined XMOUNT requires a string variable to contain the device specification and another string variable that will contain the volume ID of the newly mounted disk XMOUNT will return an error code in a variable that should be of type MOUNTERROR VAR DEV VOLID STRING 10 RETCODE MOUNTERROR Next the function XMOUNT must be defined as follows EXTERNAL FUNCTION XMOUNT D STRING VAR V STRING MOUNTERROR LSI XMOUNT will include the required TYPE and EXTERNAL FUNCTION definitions required by XMOUNT XMOUNT 1s then called via RETCODE XMOUNT DEV VOLIDO SYSTEMS FUNCTIONS AND PROCEDURES Page 14 10 Where DEV is a string containing the device to be mounted LE Gu DEV DSK3 and WOLID is the string variable used to receive the volume Ib if any 14 7 2 Unmounting a Disk A disk may be unmounted by specifying U after the DEV spec i e RETCODE XMOUNT DSK23 U VOLID If a disk is to be unmounted the U must contain an upper case U When yo
26. that iS in decimal notation the number would be 2405 3 A positive number after the E telis you how many places to shift the decimal point to the right in order to read the number in decimal notation a negative number tells you how many places to shift the decimal point to the left For example to represent the number 5 678E 2 in decimal notation shift the decimal point to the Left two places 0 0567 AlphaPascal generally uses decimal notation to display real and integer numbers Of course if the number is integer no fractional part is shown However if a number is too large or too small to represent easily in decimal notation AlphaPascal displays it in scientific notation You may use either scientific or decimal notation when entering numbers to a Pascal program or within the program itself For information on using the WRITE and WRITELN procedures to format numeric and character output see Section 10 1 5 5 Formatting Output 5 6 2 STRINGS A string is a group of characters These characters may be numbers Letters or any combination of characters including the delimiters for a comment or A string is identified to Pascal by enclosing it in single quotation marks For example GENERAL INFORMATION Page 5 11 This is a string Data 1231 The END i near The characters in a string represent themselves rather than numeric values reserved words etc For example the third example
27. the error you can disregard that information Now you may type a RETURN to resume program compilation or you may type a Control C hold down the CONTROL key while you type a C to interrupt the compilation If you type a Control C CMPILR displays the message Compilation aborted and then returns you to AMOS command level If you type a RETURN CMPILR resumes the compilation and then returns you to AMOS command level in either case because an error has occurred PCL does not go on to Link the program and you are returned to AMOS command level Tf CMPILR reported something other than No compilation errors your program is incorrect You should use VUE on the orogram and check your copy Changed 30 April 1981 GETTING STARTED Page 2 8 of the program against the one in this book Correct any discrepancies and use the PCL command file again For full information on using CMPILR and its options refer to Section 4 3 The AlphaPascal Compiler That section also discusses the compiler display Let s say that your program has compiled without error PCL DO goes on to invoke the Linker PLINK At this point CMPILR has created three intermediate files SALARY POT SALARY PO2 and SALARY PO3 However your program still is not completely ready to run PLINK will fully resolve references within the intermediate files and will produce the final executable PCF file The second part of the screen display that you see looks somethi
28. there are minor Limits on the size of components of those programs 1 The object code version of any one procedure may not be larger than 2000 bytes 2 You may not have more th n 255 global procedures and functions in any one program or library 3 Any global procedure or function cannot have more than 255 Local procedures or functions 4 Maximum nesting of program block declarations is 15 5 Maximum nesting of procedures WITH DOs and RECORD type descriptions is 12 4 1 4 Memory Requirements Because AiphaPascal uses a virtual memory paging system there is no Limit to the size of your programs However a certain amount of memory is required to use CMPILR PLINK and PRUN Although the minimum size of your memory partition depends on the data space requirements of the Pascal program you want to use you should have at least 16K of memory to run a small program To compile and Link a program you should have at least 24K of memory OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 5 Also you should note that even though you may execute a program that is Larger than your memory partition the larger that memory partition is the less paging must be done and in general the faster your programs will run To help even more in speeding up orogram execution and in reducing the minimum memory partition size remember that you may load PRUN PRGEL1 4 into system memory Also if the assembly Language subroutines that y
29. which are to be indexed by the numbers 1 through 10 The elements are of type INTEGER 6 5 VARIABLE DECLARATIONS Pascal requires that all variables be declared This means that you assign a name to a variable and permanently associate a data type to that variable Since you tell Pascal the data type of each variable Pascal knows what operations can be performed on that variable and which functions and procedures can be used on it Be aware that Pascal does not assume an initial value e g zero for a declared variable you must explicitly assign a value to a variable If you try to assign a value that is not consistent with the data type associated with that variable the Pascal compiler generates an error message The variable declaration statement takes the form VAR identifier identifier data type identifier identifier dat type identifier identifier data type For exampie DECLARATIONS AND DEFINITIONS Page 6 6 VAR TestScores Variance Mean REAL StudentID ClassName StudentName Teacher STRING Passed BOOLEAN The variable name may be any Legal identifier The data types you can assign to a variable are discussed in Chapter 7 Data Types 6 6 FUNCTION AND PROCEDURE DECLARATIONS You may often need to perform the same sort of actions on a body of data throughout your program Rather than forcing you to tediously duplicate one piece of code every piace it is needed Pascal gives you tw
30. you might want to say TOTAL SUM Or you may want to break your programs up into modules For information on modules see Section 6 1 Program Declarations Of course if you want your programs written in standard Pascal so that they can run with other Pascal implementations you may want to restrict your programs to using features found only in standard Pascal CHAPTER 4 OPERATING INSTRUCTIONS AND CHARACTERISTICS This chapter assumes that you are ready to start compiling and running Pascal programs If you are not familiar with AlphaPascal you may want to skim through Part II Summary of AlphaPascal before you attempt to start using the AlphaPascal system This chapter gives you information that you will need to know about the programs that make up the AlphaPascal programming system The first few sections talk about file and memory requirements Operating instructions begin with Section 4 2 Creating a Pascal Program The AlphaPascal system consists of the compiler CMPILR the linker PLINK the run time package PRUN and the standard external Library STDLIB To create a Pascal source program use the system screen oriented text editor VUE VUE is an easy to use powerful editor that allows you to see your Pascal program on the screen of your terminal and to make changes to that program by moving the cursor around on the screen display and entering the new or replacement characters For information on us
31. 1 8 REWRITE The REWRITE procedure opens a file for output In effect it performs a CLOSE followed by an ERASE then it opens the file for output The invocation takes the form REWRITECfilec identifier2 where file identifier is a file variable that is associated with the file you want to rewrite REWRITE has the ability to generate file names if no file specification is associated with the specified file identifier These file names begin with TEMPAA TMP and go on to TEMPAB TMP TEMPAC TMP sae TEMPZZ TMP For example the program PROGRAM TestRewrite VAR NewFile FILE OF CHAR BEGIN TestRewrite REWRITE NewFile No file specification associated with NewFile 3 PFILE NewFile Print filespec now associated with NewFile END TestRewrite h prints Q VEMPAA TMP INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 14 10 2 SPECIAL FUNCTIONS AND PROCEDURES FOR FILE 1 0 Standard Pascal gives you several functions and procedures that allow you to read and write data from a file Cesga GET PUT READ etc We talked about these routines in the sections above Although you will often use most of the functions and procedures discussed in those earlier sections to transfer data between the terminal and your programs AlphaPascal also provides a number of additional functions and procedures that allow you to work with AMOS disk files Using the functions and procedures we discuss below you can search for define
32. 1 ASSIGNMENT STATEMENT The assignment statement assigns a value to a variable It takes this form variable expression Pascal evaluates the expression on the right side of the assignment operator symbol 15 The variable on the left side of the assignment operator then assumes the value of that expression Note that all variables to which values are assigned must have been previously declared For example given that your program previously contained the statement VAR AccountNum INTEGER the statement AccountNum 102441 assigns the integer value 1025 to the variable AccountNum For more information on the assignment operator see Section 8 2 Assignment Operator That section also discusses the use of the assignment operator in expressions discusses the precedence of the assignment operator and describes the AlphaPascal modifying assignment operators 9 2 PROCEDURE CALLS Procedure invocations may appear as program statements For information on procedure parameters see Section 6 6 1 Formal Parameters Liberal use of procedure calls in your programs illustrates one of the important features of Pascal modularity Given the appropriate procedure definitions a main program can be extremely easy to read For example Page 9 2 BEGIN Mair Openf i ventory part Compute which ee we are Low on and write to file p PrintR t Date LowFile END Main Inventory UY f s ng 4
33. 5 through 13 which give detailed discussions of the AlphaPascal statements and procedures you may want merely to turn to Appendix A A Quick Reference to AlphaPascal to get an idea of the functions and procedures included in this implementation of Pascal After you are somewhat familiar with the AlphaPascal system you may want to read Chapter 15 Writing and Modifying an External Library File If you are a systems programmer you may want to read Chapter 16 Assembly Language Subroutines IF YOU ARE NEW TO PASCAL You will probably want to read Chapter 2 Getting Started which gives a brief discussion of Pascal and goes through a quick demonstration of building compiling and running a small simple Pascal program Next you will probably want to start reading Part II Summary of AlphaPascal for information about this versian of the Pascal Language When you are ready to begin writing Pascal programs turn back to Chapter 4 Operating Instructions and Characteristics for information on using the AlphaPascal compiler and run time package NOTE We would appreciate any comments or suggestions note the Reader s Comments Form in the back of this book INTRODUCTION Page 1 3 1 2 PASCAL BIBLIOGRAPHY The most important source book for Pascal programmers containing the definition of standard Pascal is Jensen Ka and Wirth Na Pascal User Manual and Report Second Edition Springer Verlag 1976 I
34. Case Letter m 155 109 6b Lower Case Letter n 156 110 E Lower Case Letter o 157 111 Lower Case Letter Pa gt a oo paa THE ASCII CHARACTER SET Page B 5 OCTAL DECIMAL HEX MEANING p 160 112 70 Lower Case Letter i a 161 11433 74 Lower Case Letter r 162 114 72 Lower Case Letter s 163 115 73 Lower Case Letter t 164 116 74 Lower Case Letter u 165 TES 75 Lower Case Letter v 166 118 76 Lower Case Letter w 1467 119 7T Lower Case Letter x 170 120 78 Lower Case Letter y LM 121 79 Lower Case Letter z 172 122 7A Lower Case Letter 173 123 B Opening Brace 174 124 TC 1 Vertical Line 175 125 7D Closing Brace 176 126 7E Tilde DEL 177 127 TF Delete M art O e ME ON O A HH Oc O qn O NPA cuo SONO NO NO a EN ERD SA uns APPENDIX ALPHA PASCAL COMPILER ERROR MESSAGES Below is an alphabetic list of all error messages output by the ALphaPASCAL compiler For a discussion of how to compile programs and for information on error reporting and error recovery see Chapter 4 Operating Instructions and Characteristics We believe that the error messages below are very helpful in explaining exactiy what part of your program caused the error Therefore we have not provided detailed explanations for each error message For some of the messages be
35. Employee EmpRecord BOOLEAN Adds specified employee record to EmpFile Returns false if no room remains to add recordat VAR BEGIN InsertionPointFound BOOLEAN NewRecNum INTEGER Ada TRUE RecNum ControlRecord FirstdataRecordiEmployee NamesLasti117 PreviousRecNum 3 0 InsertionPointFound RecNum 0 WHILE NOT InsertionPointFound DO BEGIN SEEK CEmpF i le RecNum GET CEmpFile IF NamePrecedesName Employee Name EmpFi le Name THEN InsertionPointFound 5 TRUE ELSE BEGIN PreviousRecNum RecNum RecNum EmpFile NextbataRecord InsertionPointFound RecNum 0 END i END Search for insertion point IF RecNum lt gt O THEN IF SameNames Empioyee Name EmpFile Name THEN BEGIN Employee NextDataRecord EmpFile NextDataRecord EmpFile Employee PUT CEmpFile EXIT Add END IF O NewRecNum ControlRecord FirstUnusedRecord THEN BEGIN Add False EmpFile is full EXIT CAdd END SEEK CEmpFile NewRecNum GET CEmpFile ControlRecord FirstUnusedRecord EmpFile NextUnusedRecord EmpFile EmployeeRecord EmpFile NextDataRecord RecNum PUT CEmpFile INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 34 IF PreviousRecNum Q THEN BEGIN SEEK EmpFile 0 control Record FirstDataRecordLEmployee Name Lastt111 NewRecNum EmpF ile ControlRecord PUT EmpFile END ELSE BEGIN SEEKC EmpFile PreviousRecNum GET CEmpFile EmpFile NextDataRecord New
36. FUNCTIONS c onnaconmanonasna ALS aree T2 1 1 COSC oreet a chow D 125152 SINO ws bw a wa dra EORR UR PDT A TANO E IPA id E RUE SIUS 12 1 4 ARCCOSOO ganannannaaamosasounasarm a VELA ARCSIN O ii TESTS ARC TANCK aa a a e 12 2 HYPERBOLIC TRIGONOMETRIC FUNCTIONS panatauane lo 21 COSH qv Siete eee wi Seer E 12 2 2 SINHOO a E are tardes TANHOXD cix RR AO ales 12 2 4 ARCCOSH X vana amenn Emen PANA ca 12 2 5 ARCSINH X woauvvccccnnnanssenanuene 12 2 6 ARCTANH OO AAA A 12 5 MISCELLANEOUS MATHEMATICAL FUNCTIONS WE RUN eq 12 3 1 ABSUX AA AT PAA Vea Sa EXPCK aaa A PA dea irse EXPONENT OX dae o re 12 5 4 FACTORTALEX onooc os susce a PAM aa 1255 5 EN is An o a adan e aaa 10 2 19 SEEK ecce eee ue hh S seansas 12 5 6 LOG XD rococcnnnconacnroanannnoanaron Changed 30 April 1981 Page vii 10 27 10 27 10 29 10 29 10 31 10 38 10 38 10 38 10 39 11 1 11 1 11 2 11 2 11 3 11 3 11 4 11 5 11 5 11 6 11 6 11 7 11 7 11 7 1 8 11 9 ALPHA PASCAL USER S MANUAL Page viii 12 5 7 0DDOO ve AAA nano 1274 A E A A 12 4 12 5 9 PWROFTENCX co cc cece cee Civi ud cares ASS O 12 5 10 PWROFTWOQD aneconcononana m sess Vers 12 5 11 RANDOMIZE J cnc nccecace aa hee A AAA a ey wield org a M E WR 12 5 12 53 13 ROUNDOO a een ee sa aen s DOO 12 3 14 SHIET X Y dra ee e 12 6 12 5 15 SGROD ness NS Ai 12 6 NGA TO SORT OXI AS a d 12 3 17 STROO and STR
37. LOCKARRAY LARRAY Be sure to set up type LARRAY as an array large enough to hold the maximum number of possible locks on your system Since there is no range checking in external procedures or functions LARRAY must be Large enough to receive the maximum number of anticipated locks Therefore it is a good idea to set LARRAY to the number of queue blocks allocated in your system 1f there is a possibility that more than 25 locks may be set at a time when GETLOCKS see below is called then it is necessary that the size of LARRAY be increased The file DSKO XLOCK INC 7 51 which contains the definition of LARRAY may be modified To get a List of locks enter into your program GETLOCKS LOCKQTY JOBNUM LOCKARRAYO Where LOCKQTY is an integer that receives the number of set Locks JOBNUM is an integer that receives your job number and LOCKARRAY is the array that receives the list of locks SYSTEMS FUNCTIONS AND PROCEDURES Page 14 9 One thing you might do with this List of Locks is List it To do this FOR LOCKLIST 1 TO LOCKQTY DO WITH LOCKARRAYTLOCKLISTI DO BEGIN LIST LOCKS M TIWRITELN JOB J08 WRITELNC LOCK LOCK1 WRITELNC LOCK2 LOCK2 END LIST LOCKS nod 14 7 XMOUNT XMOUNT is an assembly Language routine that allows you to mount a disk from within a Pascal program without Leaving Pascal You should call it whenever you change a disk and your Pascal program is going to use that disk You
38. STR I Dh Paw ege aa oe o 11280 TAN a ces vac ar a aa mn dad N22 TANH m du od oho a a 10 2 TRUNG Cour uo de Ue peg des aL rac OST MAXINT eis doo 3 decem uou 606 BAL MEMAVAIL pa we mama o wow le Modifying assignment operators 3 2 8 4 Modifying STDLIB a s s a s 16 4 MODULE e aa aa QUE MOUNT INC a nonoo e a a a o a 14 10 Mounting a disk s e s s s a e a 149 MOVELEFT amp s aS ne ae o 13 8 MOVERIGHT a ew o 13 9 Multi dimensional arrays a 7 10 Multi user file Locks a a a noun 245 Multiple libraries oso o 316 1 Napierian logarithm s a s e s s 1274 Natural Logarithm s a s s 12 4 NEW lara a a c dac da uw IA A A AS NIL u Ka o a eG a ee xa Non local reference a a s e a 5 7 NOT uu a a on ox Ic 3 Null statement s a e 9 5 Numbers ita Wege woe s x owe 5 9 Numeric constants a s a a s 6 1 Numeric Literals s eaa 6 4 Numeric notation s s a a 5 9 Changed 30 April 1981 ALPHA PASCAL USER S MANUAL Page Index ODD AA A Tah OPEN we we ros 10 16 10 25 Opening files s s s s s a 10 16 OPENO a esc ow xo uxo eo 10525 OPENR Qu ma xoc ox we ag 10 26 Operator o s eas r a a a Bm Operator precedence s s s e 373 8 1 to 8 2 OR hide a a a IRI CUTS ORD we Mac Rl ee a Ss Ue en e a Sep Eae TTR OUTPUT es epee Ga Bia ee 027 PACK e x Wo dec Owe Sk Packing data a e a s s a 7 8 PAGE 2 o ge aa
39. TOD Returns time of day in seconds as a real number UCS Procedure to convert upper case characters to lower case WL N Routine used by WRITE WRB Routine used by WRITE WRC Routine used by WRITE WRI Routine used by WRITE WRR Routine used by WRITE WRS Routine used by WRITE XERRORTRAP Special version of error handler XLOCK Procedure to set or release file Locks XMNT Routine used by XMOUNT must not be called directiy XMOUNT Procedure to mount a disk 16 2 WRITING LIBRARY FILES It is not likely that you would want to dispense with the standard Library file altogether since the compiler relies on the presence of many of the procedures and routines in that Library If you did not use STDLIB you would have to duplicate for yourself all of the routines Listed above that make up that Library However it is possible for one library to make use of another For example suppose you want to write your own library which contains a set of functions that are particularly useful for the programs that you write e g You need a set of routines that construct and display screen menus you can write such a library then when you link it you can specify the STDLIB external Library as its library file The only time you ever Link a file without specifying a library is when you are linking a root library such as STDLIB itself a very rare occurrence In this case your library file perhaps named NEWLIB would be Linked with STDLIB Then when you Link a n
40. X a D sansan AR 12 6 12 5 18 TRUNCOO a Mes 12 4 SAMPLE PROGRAM TO PAD A NUMBER WITH LEADING CEROS aia wes is A a aw ea 12 6 CHAPTER 15 STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES 13 1 STRING INTRINSICS n e 13 2 tantet CONCAT Siue pw Bus arb Cog RUND AA GUN wow air 13 2 13 1 2 COPY l2 x APA e ERRORS EE eae 13 2 Satit DELETE am a EIS 1 3 TS Lot INSERT uuo mes ET m RUE iN RET RE wwe 15 4 13 145 LCS i v ee ob Fa a cp UR Once m WORT AIMER ROM RC ne 03 4 15 1 6 LENGTH o ooanos a AA x Re Trakat POS LA saw aa Aia PAGPAG MANA 13 5 Tae eho STRIP aa CR NS A M ec eov Reo ER Toe aD A Aa ow a SAA COS VAL ds 2 13 68 13 2 CHARACTER ARRAY INSTRINSICS a e nohuccces 1577 15 62 ETULCHAR Gasa eonun boa E TEN 013 7 13 2 2 MOVELEFT and MOVERIGHT o oononnnana 13 7 5 045 SCAN SS uve ads REPE saga magaang VOT PART III ADVANCED PROGRAMMING ON THE ALPHA PASCAL SYSTEM CHAPTER 14 SYSTEMS FUNCTIONS AND PROCEDURES 14 1 LOCATION wm SUR AUR UR US R aa T SIN MUTET 14 1 14 2 SIZEOF AR AAA m a alee M acm ame 14 1 14 3 MEMAYRIL AA aaa AE T 14 4 MAINPROG ncnscavcne GC Nee eiue ah AA ca Lei etek a 14 2 TAGS SPOOL vw mune sen Rut Area PISIS QUU OUR G usu ie ena ee 14 3 Tav UTE Suae gea lera e a en cr Rn a LATA 14 5 2 Error codes EE 14 4 14 5 3 Function definition ocencoonnosanona 1474 14 5 4 The SPOOL subroutine na Thanh 14 6 XLOCK AND GETLOCKS nanasoonnaa aise A iui qa ia
41. You may select one or more of these options at compile time by including the appropriate option codes in your program You tell the compiler that you want to make an option request by including the symbol S at the front of a program comment followed by the specific option code you want to use The compiler acts upon the option requests as it reaches them in the program Option codes may be in upper or lower case No space may separate the left comment delimiter and the option code For example 18G 3 is valid but 6 is not 4 5 2 1 The GOTO Options G and 6 The G code tells the compiler to allow use of the GOTO statement the G code tells the compiler to generate an error message if it encounters a GOTO statement You may use these options to turn GOTO recognition on and off within your program The compiler uses the G option as the default that is it does not recognize GOTO statements unless you use the 6 option 3n your program 4 4 2 2 The Include Option SI The I code telis the compiler to include the contents of the specified file in your program Supply a valid AMOS file specification For example CEI MACRO INC The default extension is INC The SI option code tells the compiler to physically insert the contents of the specified file into the file being compiled The insertion takes place at the point of the option request You may not include any other option codes after the file specification The C
42. a amp 2 x s Image mode s s s oo Include file a a a a Include files 9 Indentation conventions s a s e 5 4 INFOREC L uu a Goes tue fe AA INPUT zo x laa Se es te E INSERT Banig de Xo dL APO ee 13m4 INTEGER maaawa aa wa 67 7 2 15 4 Integer numbers a s s e 5 9 10 10 INTERACTIVE a X wow cx ces Ss cv cT Invoking functions a s s s 6 7 JOBDEV JOBUSER uu naaa maa ow 106235 maaawa na 10 24 RED d na KEYBOARD uo 2 2 2 2 10 2 10 14 nog a e 106P 11 6 ALPHA PASCAL USER S MANUAL Keywords um so s a a ARRAT uw ox E se BEGIN og ade a CASE Cy 2 1 2 de CASE OF a ovo vos CONST Ce ov ow 4 END V fie We ww la ee EXTERNAL a s ea FILE a c FOR DOS Sa WE ae FORWARD a FUNCTION a GOTO oq a X s te LE STREN 4 X 2 w c IF THEN ELSE LABEL 2 ox MODULE s ao wa PACKED ye var es et s PROCEDURE na a a PROGRAM won RECORD a REPEAT UNTIL a SET asa Sa VAR so uo Pe dtes ada WHILE DO gt a s a WITH D0 4 vox Xo KILCMD do kx wt G Label declaration a EES Fox Lah a ten seme ve Legal identifier a LENGTE Wu ee va el Library verston checki Line printer spooler Linked List s a a o Linker CQ wa a wo Linking a program Linking a single file EN ed wee wee EDO a 7g LOAD uve v vow So ee Local procedures Local reference LOCATION LOG cas cw a D
43. and abort the compilation because you tried to create the file in an account outside of the 100 project area You may use the codes L and L to turn program Listing off and back on again For example suppose you have a long program that contains a large section of comment that you don t want in your listing file At the front of your source program you might say CSL MYPROG Directly in front of the section you do not want in your Listing you would place SL Y At the point where you want the listing turned back on again place M The compiler tells you in the diagnostic display that it is writing a Listing file For example Changed 30 April 1981 OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 9 amp iphaPascal Compiler Version 2 0 lt 0 List to LIST ERRCHECK D gt mmm PROGRAM Bb ma maam 20 Lines 12 36 seconds 96 90 Lines minutes No compilation errors If you want the listing to appear on your terminal screen use the device specification TTY For example L TTY NOTE This display will be intermingled with that of the diagnostic display unless you send the diagnostic display to a file see Section 4 3 1 The Diagnostic Display No other option requests may appear after the L option The listing consists of a display of your program with additional information to the left of the program If your program contains errors the Listing file contains the appropriate error messa
44. can t open an open file It also makes the file identifier available for association with a possibly different AMOS file Files are automatically closed when you leave the procedure in which they were declared A simple case of opening and reading a file might look something like this VAR CustID FILE OF STRING Declare file identifier gt UserFile STRING a 9 BEGIN TestFile gt WRITEC Please enter name of your data file 2 READLN UserFile OPEN CCustiD UserFile INPUTO Open the file get the data gt WRITE CCustID Display data in buffer 5 CLOSE CCustIDO Close the file END TestFile The small program above asks the user for a file specification and opens that file The actual process of using the OPEN procedure inputs the first record of that file into the buffer variable automatically assigned to the file identifier CustID 10 2 2 CLOSE You will use the CLOSE procedure to close a sequential file that is open for output Closing the file ensures that the last record will get written ta the file it also enters the file into the disk directory You may not OPEN a file that is already open so if you have been using a sequential file for output and vou want to use it for input vou must first close it and then re open it for input The invocation takes the form CLOSE Cfile identifierd where file identifier is the file variable associated with the AMOS file you want to close For example
45. computed answer to the terminal display For information on Pascal program statements and procedures see Part II Summary of AlphaPascal GETTING STARTED Page 2 4 NOTE So that we could identify specific Lines of the program to you we mentioned identifiers such as first Line or fourth Line This was for our convenience only the Lines in Pascal programs do not ordinarily start with numbers 2 3 BRIEF DEMONSTRATION Now that you ve taken a Look at a small Pascal program we would Like ta walk you through a brief demonstration of building compiling Linking and running the program We Ll assume that the computer and your terminal are on and that you have been assigned an account in which to work Make sure that you are at AMOS command level that is that you see the prompt symbol that indicates that you are communicating with the operating system First log into the system by typing LOG followed by the device that contains the account you want to tog into and then entering the number of that account Then press the RETURN key on your terminal For example if you want to work in account 20 3 on device DSK1 enter LOG DSK1 20 3 Now you see something like Logged into Dsk1 20 3 You can now begin to create your Pascal program 2 5 1 Building a Pascal Program To build a Pascal program use one of the system text editors to create your program as a text file If you are using a video display terminal
46. examples given in this appendix A 5 2 2 Conditional Statements conditional statement contains statements whose execution depends on the result of a conditional test These statements may take the form XF Boolean expression THEN statement or IF Boolean expression THEN statement ELSE statement or CASE expression OF casel label statement1 case2 label statement caseN label statementN END Several case labels separated by commas may be written in place of a single case label QUICK REFERENCE TO ALPHA PASCAL i Page A 11 A 5 2 3 Repetitive Statements WHILE Boolean expression DO statement or REPEAT statement list UNTIL Boolean expression or FOR variable identifier expression TO expression DO statement ora FOR variable identifier expression DOWNTO expression DO statement A 5 2 4 WITH Statement The WITH DO statement allows you to access record fields as if they were simple variables WITH record variable1 record variable2 record variableN DO statement Changed 30 April 1981 QUICK REFERENCE TO ALPHA PASCAL A 6 ALPHA PASCAL STANDARD FUNCTIONS AND PROCEDURES Below is an alphabetic List procedures that you may use ABS ARCSINH CHR COS DELETE ERROR EXP FILLCHAR GETFILE JOBDEV LENGTH LOG MEMAVA TI ODD OPENR POS PVIRT RANDOMIZE RENAME ROUND SHIFT SPOOL STR TANH Ucs XEQERR ARCCOS ARCTAN CLOSE COSH EOF ERRORINFO EXPONENT FILESIZ
47. feed pair Given READLN Data Line where Data is a file variable READLN performs the following actions Line Data WHILE NOT EOLN Data DO GET Data GET Data in other words until we reach the end of the Line a carriage return line feed pair read data into the variable Line The invocation takes the form READLNCfiLe identifier list of variables INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 9 where file identifier is a file variable associated with the file you want to read from If you omit the file identifier READLNCList of variables READLN reads from the pre declared file INPUT that is it reads from the terminal Separate READLN arguments with commas 10 1 5 3 WRITE The WRITE procedure writes a List of expressions to a file or a terminal display To print a string enclose it within single quotation marks You must oniy use WRITE for TEXT files WRITE does not write an end of Line marker carriage return line feed pair after writing the specified data To begin a new line use the WRITELN procedure The invocation takes the form WRITECfiLecidentifier expression List2 where filecidentifier is a file variable associated with the AMOS file you want to write the data to and expression list is the data to he written The expression List may contain string literals constants variables of type INTEGER REAL CHAR PACKED ARRAY 1 n OF CHAR and STRING For examples WRITE QNew
48. given INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 18 VAR TaxRecs FILE OF CHAR once we have opened and used the AMOS file associated with TaxRecs we must close it CLOSE TaxRecs AS your program Leaves each procedure or function any files declared in those routines are automatically closed for you However using the CLOSE procedure ensures that if you are forced to do a hasty and untidy exit from your program for example if a system error occurs the last record of the file will be written when the CLOSE procedure is executed Closing a fite also makes its file identifier available for use with another file 10 2 3 CREATE ALL random files must be pre allocated on the disk before you can use them That means that their maximum size must be established before you use them You can copy random files to sequential files and vice versa so if you are in doubt about the ultimate size of a file that you are building it is a good idea to write the data to a sequential file first then copy the file to a random file after you know how many records have to be copied The CREATE procedure allocates a random file The invocation takes the form CREATE file identifier s ze where file identifier is a file variable associated with the AMOS file you want to create and size is a variable of type INTEGER that designates the number of disk blocks you want the file to contain NOTE You must associate an AMOS file specificatio
49. inclusion Greater than or equal Cor set inclusion IN Set membership A 4 1 4 Logical Operators NOT Negation OR Disjunction AND Conjunction A 65 1 5 Set Operators Union Set difference Intersection QUICK REFERENCE TO ALPHA PASCAL Page A 8 A 4 2 Constants ap Constants may consist of Characters and strings of characters in quotes TRUE and FALSE MAXINT which evaluates to the Largest integer on the AMOS system 32767 Values of user defined types Integers Decimal and exponential numbers If a number contains a decimal point at Least one digit must appear to the left of the decimal point The exponent in an exponential number is identified by the E symbol For example 36E 5 represents 0 000034 Asda Variables variable is a simple identifier an indexed variable of the form array variable indexl expression indexN expresion a referenced variable or file buffer variable of the form painter variable or file variable or a field designator of the form record variable field identifier A 4 4 Function Calls Function calls have the form function identifier ori function identifier parameter parameterN QUICK REFERENCE TO ALPHA PASCAL Page A 9 A amp 5 IF THEN ELSE and CASE OF Constructs in Expressions AlphaPascal allows you to use the IF THEN ELSE and CASE OF constructs to conditionally evaluate one of two in the case of the IF THEN ELSE o
50. make the program hard to read and maintain you may designate this piece of code as a procedure The procedure declaration names the procedure tells what kinds of variables it will use and gives the statements that make up the procedure It takes this form PROCEDURE procedure name formal parameters procedure block DECLARATIONS AND DEFINITIONS Page 6 9 The formal parameters list the variables and their types with which the procedure will work For example PROCEDURE PrintReport Title STRING PageSize INTEGER The procedure block takes this form Label declarations Constant declarations Type declarations Variable declarations Procedure function declarations BEGIN END block F To invoke the procedure include the name of the procedure within your program Unlike a function invocation a procedure invocation is a program statement not an expression For example say that you have a procedure named Shuffle that simulates the shuffle of a deck of cards BEGIN IF Dealer New OR Deck Empty THEN Shuffle END Although a procedure may take a form very much Like that of a function it does not necessarily return a value Notice that it also does not have ta accept any arguments For information on using procedures to return several results see Section 6 6 4 2 Reference Parameters 6 6 3 Forward Declarations What happens when a procedure or function declaration invokes a procedure or function
51. numbers and the keyword PACKED in the type declaration for such data types has no effect DATA TYPES Page 7 8 Your program does not need to handle packed data type differently than any other data type NOTE Standard Pascal requires that you use the UNPACK and PACK standard procedures to convert between packed format and a format that your program can read and write AlphaPascal performs this conversion for you automatically In fact AlphaPascal does not support the PACK and UNPACK procedures Although you do save memory space by packing a data type be aware af the fact that your program will run slower when it handles such a data structure because of the time required to unpack and repack data T 2 2 ARRAY An array has a fixed number of components which may be accessed in any order by referencing the Location of the element within the array To reference an element of the array you give the name of the array and the array index sometimes called a subscript which selects the location within the array whose contents you want to access The subscript appears after the array name in square brackets Arrayrnamel Index1 Index2 IndexN where each index is a simple type For example suppose the array PartNos contains thirty part numbers and you want to see what the twentieth one is You would access the twentieth location in the array by saying WRITELN PartNosl201 or perhaps WRITELN PartNosL2 Offset ALL e
52. perform a numeric operation on the value Notice the use of the optional parameters 8 2 in the Last WRITELN invocation to format the numeric answer in a field eight characters wide with two digits to the right of the decimal point A sample run of the program looks Like this Enter price of object 560 The price is in whole dollars With 6 tax the price is 593 60 O Changed 30 April 1981 STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 7 15 2 CHARACTER ARRAY INSTRINSICS The procedures and strings listed below are for use on packed arrays of type CHAR You must make sure that any string literal you assign to the array is the correct number of characters For example asssigning a string literal to an array of 24 elements will cause an error if that string literal has less than or more than 24 characters 13 2 1 FILLCHAR The FILLCHAR procedure modifies a character array by filling it with the specified character The invocation for the procedure takes this form FILLCHAR Destination Length Fillrcharacter where Destination must be a variable For example PROGRAM TestFiliChar VAR Destination PACKED ARRAY 1 101 OF CHAR Length INTEGER Character CHAR I INTEGER BEGIN TestFiliChar gt Length 10 Character A FILLCHAR Destination Length Character FOR I 1 TO 10 bo WRITE DestinationLI1 END TestFillChar gt The program above fills the character array Desti
53. procedure Begin at the caller of the procedure which set X to ERRORINFO 14 10 4 ERROR The procedure ERROR x takes an INTEGER x as argument and generates the corresponding system error See the previous section for the list of error codes CHAPTER 35 ASSEMBLY LANGUAGE SUBROUTINES Assembly Language subroutines are assembly Language programs that are callable by your AlphaPascal programs Why would you want to call assembly languages routines from a Pascal program There are at least two good reasons Firstly mot all the capabilities of the operating system AMOS have been directly included in AlphaPascal The ability to write assembly Language subroutines allows you to enrich AlphaPascal as need requires with additional capabilities Secondly routines written in assembly language execute significantiy faster than routines written in Pascal Thus you may wish to identify key functions and procedures which are bottle necks in your programs and rewrite them in assembly Language This chapter describes how to write and use assembly language subroutines It will be assumed in this chapter that you are an experienced assembly Language programmer on the AMOS system For more information on assembly Language programming please refer to the AMOS Assembly Language Programmer s Reference Manual DWM 00100 432 the WD16 Microcomputer Manual DWM 00100 04 and the AMOS Monitor Calls Manual DWM D0100 42 15 1 CALLING AS
54. red The records may be set up this way TYPE Carinfo RECORD Model STRINGE31 Year INTEGER Color STRINGL31 SerialNumber INTEGER END 1 record J VAR Counter farNumber INTEGER CarLot ARRAY 1 100 OF Carinfo Now you can process them Without using a WITH DO statement you would have to do something like this STATEMENTS Page 9 11 Counter D FOR CarNumber 1 TO 100 BO BEGIN IF CarLot CarNumber Models X20 AND CarLot CarNumberl Colorz red THEN Counter 1 WRITELN Number of red X20s is Counter END A more convenient way is to use the WITH DO statement Counter 0 FOR CarNumber 1 TO 100 DO BEGIN WITH CarLotLCarNumberi DO TE Modelz X20 AND Colorz red O THEN Counter 1 WRITELNC Number of red X20s is Counter END By specifying more than One variable identifier you can use the WITH DO statement to access fields that occur within record fields For example to access data in the record CarLot Make Model you could write something like this WITH CarLot Make DO Model HatchBack This is equivalent to WITH CarLot DO WiTH Make DO Model HatchBack CHAPTER 10 INPUT OUTPUT FUNCTIONS AND PROCEDURES The functions and procedures discussed in this chapter are used to transfer data between your programs and the users of those programs and between programs and files The routines we describe in the first part of the ch
55. sequential file has been reached INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 16 10 2 1 3 Logical Records Within each disk block of a file you can have one or more logical records The size of a Logical record is determined by your programs For example if a grouping of data in your data file is CustomerName 30 bytes CustomerAddress 50 bytes and SocialSecurity 9 Dytes your file logical records might be 89 bytes For information on blocking logical records into disk blocks see Section 12 2 5 CREATE A random file record may not be targer than 512 bytes and maximum random file size is 65535 records A sequential fite Logical record can cross biock boundaries and so may be larger than 512 bytes 10 2 1 4 Opening and Setting Up Files The usual sequence of events for opening and using a file goes this Way 1 Declare a file variable For example VAR DataFile FILE OF CHAR This variable establishes the file channel the communication Line over which your program will transfer data in and out of the file associated with that channel In our discussions below the term file identifier refers to the file variable associated with the actual AMOS file 2 Before you can use an AMOS file you have to associate the specification of that file with the file identifier you have declared and you must open the file This tells AMOS what AMOS file you will be accessing via the file identifier An AMOS file spe
56. statements within the compound statement must be separated by a semicolon For example PROGRAM Average T This program computes the average of a series of numbers gt VAR Count INTEGER Answer Total Num REAL CONST Maxval 10 BEGIN Average y Total 0 FOR Count 1 TO Maxval DO REG IN T WRITE Enter number please Prompt user for number READLN Num Get number from user Y Total Total Num Sum numbers END Answer Total Maxval Compute average gt WRITELN Average iss Answer END Average Tn the example above the statement section of the program block contains two nested BEGIN END compound statements Note that the BEGIN keyword does not require a semicolon after it and that you do not precede the END keyword with a semicolon This is because BEGIN and END are keywords but are not statements Therefore there is no need to separate BEGIN from the WRITE statement in fact doing so causes an error For the same reason do not place a semicolon between the END keyword and the statement before it 5 3 COMMENTS Sometimes the function of a section of a program is not immediately obvious to the casual observer To help the reader of a program understand what that program is doing Pascal allows you to enter comments in your program Comments are ignored by the compiler and serve only to document the source program AlphaPascal accepts as comments any text enclosed either b
57. to TRUE everything after the first THEN keyword is executed otherwise control passes to the next program statement NOTE You may include the keywords IF THEN in an expression to conditionally evaluate one of two alternative expressions See Section 8 4 IF THEN ELSE Expressions Qui tot TESTHENCELSE The addition of an ELSE clause to an IF THEN statement gives us a way to select one of two statements as a result of evaluating an expression The IF THEN ELSE statement takes the form IF Boolean expression THEN statement 1 ELSE statement 2 If the Boolean expression is TRUE the first statement is executed otherwise the second statement is executed As in the case of the simple IF THEN statement above a compound statement May appear in place of a single statement One of the two statements will always be executed For example IF Margin gt LineWidth THEN Error PGWDTH ELSE LineWidth Margin The Line above is from a program that formats documents If the value for Margin is greater than the current LineWidth then we set an error code into the Error flag otherwise we reset the LineWidth to the old value minus the Margin What happens if an IF THEN ELSE statement contains multiple IF THEN statements To which IF THEN statement does the ELSE apply For example If A B THEN IF B C THEN Flag 0 ELSE Flag i 1 Does Flag get set to 1 if A gt B or if B C AlphaPascal nests ELSEs That means that in the cas
58. to change to accommodate the changes in the procedure For more information on the external Library see Chapter 14 Writing and Modifying an External Library File OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 19 4 5 2 Interrupting a Program Whenever you use PRUN you can tell it to interrupt program execution by typing a Control C PRUN stops the program being executed and displays Interrupt Help You may enter one of four responses Q R B or followed by a RETURN Tells PRUN that you want to terminate program execution PRUN returns you to AMOS command level R Telis PRUN to resume program execution at the point of interruption B Tells PRUN to print a backtrace of all the procedures and functions invoked during the program execution to this point These procedures and functions are Listed in order with the Last called procedure or function listed first The display might look something Like this depending on the program you are executing interrupt Help B RET in STDLIB PCF RDR at IPC 33 in VALID PCF PROGRAM at IPC 43 in STDLIB PCF PROGRAM at IPC 423 Exit to AMOS interrupt w Help Q RET For information on keeping program users from using the backtrace function to see the names of the functions and procedures in your programs see Section 4 4 5 Preventing Backtracing of PCF Files the SMASH Option Tells PRUN that you need help PRUN now display
59. type definitions variable declarations external declarations procedure and function declarations A 2 DECLARATIONS AND DEFINITIONS Pascal requires that you define and declare all variables labels constants data types procedures and functions at the front of each program or procedure A 2 1 Label Declarations Labels are always unsigned integers A Label declaration takes the form LABEL integerl integer asea integerN A 2 2 Constant Definitions CONST identifier value identifier2 value 2 identifierN valueN A 2 3 Type Definitions TYPE identifier1 type Eno identifier Cidentifier3 identifiers 5 identifier5 valuet value2 sas p Wood QUICK REFERENCE TO ALPHA PASCAL Page 4 3 A 2 45 Variable Declarations VAR identifier identifier identifier identifier Rae 5 data type value1 value2 2 ao A 2 5 Procedure Declarations PROCEDURE procedure name TV BCE ka ors PROCEDURE procedure name formal parameters1 formal parametersN block l where formal parameters have the form identifier identifierN typel ors VAR identifier identifierN type A 2 6 Function Declarations FUNCTION function name result type block or FUNCTION function nametformal parameters1 se formal parametersN result type block where formal parameters have the form identifiert identifierN typel Or VAR identifieri identifi
60. ue 14 5 14 6 1 The XLOCK subroutine aaa CT 14 6 2 Setting a tock PAA PA AA 14 7 14 6 3 Setting a Lock and waiting until it is available u s 14 7 Changed 30 April 1981 ALPHA PASCAL USER S MANUAL Page ix 14 6 4 Clearing a lock 2 o oc nos acens 1478 ji 14 6 5 The GETLOCKS subroutine m u 14 9 qu 14 7 XMOUNT A EE ep juna 14 9 4 14 7 1 Error codes oooonoa corenacaenaon sa 14 10 14 7 2 Unmounting a disk doren 14710 14 7 5 Error COdes nonvcernanarnaanacacasaas ss 14 10 16 7 5 1 MOUNTED anaanano CIR PEE E 14 10 14 7 2 UNMOUNTED c a e 14 10 14 7 3 3 DEVNOTFOUND ooooooononno 14 10 14 7 5 4 BADHASH concanooonzanas Swine 14210 T 145 7 5 5 NOVOLID i unnm 14 10 TAGO TIME Naa aes m A RR beats Sere setae A 14 9 AA eee E ate hate ale IE 14 11 14 10 ERROR HANDLING PROCEDURES AND VARTABLES 14 12 14 10 17 Including ERT INC ono ocaco 14 12 14 10 2 ERRORTRAP ozcoonocosacsono 14 12 14 10 35 XERRORTRAP s e nens m Rm 14 15 14 10 4 ERROR ged Nia a ad ems ab CHAPTER 15 ASSEMBLY LANGUAGE SUBROUTINES 15 1 CALLING ASSEMBLY LANGUAGE SUBROUTINES lt anes 15 1 15 2 ARGUMENT PASSING CONVENTIONS ee o hh 15 2 15 2 1 Argument Passing sxaanaso sanda 4553 15 2 2 Data Formats canaananasaso BINALAAN 15 4 15 0 2 T1 CHAR c e R WU AW E 154 15 2 2 0 INTEGER 2 nonoansano sx oma 154 D 15 2 2 3 BOOLEAN sponornononsansanana 1274 15 2 2 4 Subranges and Scalar Types n oo
61. with a colon For example DECLARATIONS AND DEFINITIONS Page 6 2 25 IF EOF THEN WRITELN End of file To reference a labeled statement use the GOTO statement For information on GOTO see Section 9 4 GOTO In addition to the standard labels we talked about above AlphaPascal also recognizes another type of label which appears after the BEGIN and END keywords The purpose of these labels is to enlist the compiler s help in determining whether or not you are properly nesting BEGIN END blocks tf the same label appears after two BEGIN and END keywords the compiler checks to make sure that the keywords do indeed mark the beginning and end of a block if they do not the compiler reports an error ESTMBIDI Wrong BEGIN END identifier XXX expected where XXX is the block label expected This helps you to make sure that the structure of your program is correct An example may help to clarify Look at the following program diagram BEGIN Label BEGIN Label a END Label END Label The example above shows a program in which the blocks are properly nested By including the labels Labeli and Label2 we have asked the compiler to check the program structure and make sure that the BEGIN and END keywords are indeed nested properly The program below will cause the compiler to report an error BEGIN gt Riock1 BEGIN Blocke END Block END Block2 since the END keyword for Blo
62. you to enlarge the size of global variables with an update thus it is wise to avoid having global variables which you may wish to enlarge such as records strings or arrays Instead use a global pointer variable which points the desired object In this way if you change the size of the object no global variable will change size 16 3 MODIFYING STDLIB If you decide to modify STDLIB you must do so very carefully Because PLINK uses STDLIB while it is working you must not directly modify STDLIB if you want to add routines to STDLIB use the AMOS COPY command to make a duplicate of STDLIB under another name Then add vour routines to the copy of STDLIB using PLINK Finally rename your copy to STDLIB making sure to keep a copy of the old STDLIB somewhere in case of emergencies However it is far wiser to create a library which has STDLIB as its Library rather than to directly modify STDLIB Otherwise when Alpha Micro releases an update to STDLIB all your programs will need to be re linked WRITING AND MODIFYING AN EXTERNAL LIBRARY Page 16 5 16 4 VERSION CHECKING Both PLINK and PRUN check to insure that a program is only given its original Library or an update of that file since an attempt to use any other file as a library results in a system crash if you attempt to execute a program with an improper Library you will receive the error Wrong version of xxx for use with yyy where xxx is the name of your progr
63. you will probably want to use the screen oriented text editor VUE rather than the character oriented text editor EDIT BF dud The VUE Text Editor First we ll make sure that no earlier versions exist of the program we re going to create So we ll erase from the disk any file called SALARY PAS At AMOS command Level enter ERASE SALARY PAS If you s m b SALARY PAS erased Total of 1 file deleted 2 disk blocks freed GETTING STARTED Page 2 5 that means that the file did exist on the disk and that we have now erased it If vou see No files erased no error occurred it s just that no file named SALARY PAS was in the account you are logged into and so we couldn t erase it In either case you now are free to create a new file of the name SALARY PAS So enter VUE SALARY PAS BEN Now VUE Looks for the disk file SALARY PAS in the account you are logged into Since the file does not yet exist VUE says SALARY PAS does not exist create it Enter a Y followed by a RETURN to tell VUE that you do want to create a new file named SALARY PAS Now you see one or more Lines of asterisks If you do not see this display but instead see a display whose first Line begins AlphaVue n n Status where n n is the version number of VUE simply type an Escape sometimes Labeled ESC or ALT MODE on your keyboard and VUE will display the asterisks The display of asterisks means that you are in editing mo
64. 5 DSKO ERT INCE 5 DSK SPOOL INC 7 5 DSKO XLOCK INCC7 5 DSKO XLOCK SYS 1 4 DSKO XMOUNT INCC 7 57 DSKO PC DOL2 2 DSKO PCL D0L2 23 DSKO PL DO 2 23 DSK PCU D0L2 2J DSKO PU DOC2 27 The first four of these files must be on your system if you are to use the AlphaPascal system PRUN PRGL1 4 is a re entrant assembly Language program you may load it into system memory CMPILR 7 51 PLINK 7 51 and STDLIB 5 are Pascal code file programs PCF files may not he loaded into system memory DEMO PAS and DEMO PCF are the source and compiled versions of a sample Pascal program that demonstrates file handling This program also appears at the end of Chapter 10 of this book The INC files are special files you will include in programs that make use of several of the subroutines we have provided with the AtphaPascal system The special routines that make use of the INC files are described in Chapter 14 Systems Functions and Procedures See Section 4 5 2 0 The include Option 1 for information on include files The last five files Listed above are DO files these are special command files that help you to compile and Link files They invoke the compiler and Linker for you and automatically answer all of the questions asked by those programs Although these command files are not for use in all cases you will probably be able to use them most of the time when you are compiling Linking or updating a single file
65. 879 Case label a e an a FNS CAS EOE si a a a a A Deo CHAR a we a es a a AD Pes 1574 Character array functions and procedures PALLCHAR CD rar ox AA MOVELEFT a a s so ca a ae 13 7 MOVERIGHT a a a ao wt Ge s a a a e 1548 SCAN woeri m woa A SO Character editing s a 10 14 Character mode a s s a e a a s 11 6 Character set soan a ao a Feb Charmode s um aa ew nu a 10 2 10 14 11 6 CHR uan UR e u cw Tix wil eos oe C P Ded Clearing file locks s ea 14 5 Clocks System su a a so a a a a a 44511 CLOSE eas dy aa A 2017 CMPILR EE a a A Callating sequence a s s e s no Command files mau n a a Comments mo a COmpVLer dus ouk dece xo e ce dac qe c Compiler display Compiler Listing soa a s a a u Compiler options a e s s G and G nonoa so a a rono a s A CP SLE and A AO DE a ES Sat and Q s soa a s roo Rt and R a 2 s Compiling a program a tee nl we 5 Compiling a single fi le L SII Compiling updating one nodules NG Compound statement s a a s CONCAT tue lucem i oe oho CONS TT a da AL cam m rcu a ar de Constant definition s a esa Constants a s a a a A p Control C handling s e a a a 14 15 CORY ov ocu A COS X g a XR DJ a COSH a wei CREATE 2 maa wa 4 2 10 18 Creating a source file s soas a Fi CRT e a US dI a a a ELL iod Po q pasa f e Ov H gt bata objects a xw 2 5 51 Data stack
66. AGE non 4 17 4 5 1 Library Version Checking oocononn ana Sri 4 5 2 Interrupting a Program isc 4 19 4 6 HELPFUL COMMAND FILES oaceconcoranos wk aaa 420 4 6 1 Compiling a Single File PC DO 4 20 4 6 2 Linking a Single File PL DO uunnesusn 4 24 4 6 3 Compiling and Linking a Single File PCL DO ocooconoaneonos 4 21 4 6 4 Updating a Single Program Module CPUs DOJ na o id 4 44 4 5 5 Compiling and Updating a Single Program Module PCU DO E 4 22 PART II SUMMARY OF ALPHA PASCAL CHAPTER 5 GENERAL INFORMATION 5 1 BASIC STRUCTURE OF A PROGRAM 2 cncnncveceee 5 4 3 2 COMPOUND STATEMENTS BEGIN AND END 5 3 5 3 COMMENTS ual rr ata dis om fave as PA a 5 4 Ta LEGAL IDENTIFIERS sau x aaa GM EA UAE n 5 5 Sahat Reserved WOrdS Kaawaan raus RRR A A 5 6 5 4 2 Standard Identifiers cee ore 5 6 2 0 SCOPE OF IDENTIFIERS oonoooncasansonsonanonas 5 7 5 6 NOTATION A ccwcw cco censos AE E RUM wea ew aod ie m MI RA 5 9 5 6 1 NUMBERS PA EA a 58 49 5 6 2 STRINGS wisis p Wii O 5 10 CHAPTER 6 DECLARATIONS AND DEFINITIONS 6 1 PROGRAM DECLARATIONS ancoeoeneasas S aca hyena ele amp 1 5 2 CABEL DECLARATIONS crea Qu 5 So san Non p CER US 6 72 6 5 CONSTANT DEFINITIONS oonoccorsanonasononnona so O74 Gat TYPE DECLARATIONS la cod vw deere RE exe ae 6745 6 5 VARIABLE DECLARATIONS nnencescuncuns UIS 6 5 6 6 FUNCTION AND PROCEDURE DECLARATIONS AA 6 6 6 1 Functions A A o Ios 6 6 2 Pro
67. ARK LocationVl ag NEWCV1 v1 MARK LocationV2 NEWCV2 v2 Then Use RELEASE Locationv2 Use RELEASE Locationv1 RELEASE LocationV2 de allocates V2 RELEASE LocationV1 de allocates V1 VO is left on the stack in the example above You cannot RELEASE a dynamic variable in the middle of the heap you may only release variables from the bottom of the list NOTE Be very careful when using MARK and RELEASE unwise use of these procedures can leave you pointing to areas of memory that are not part of the heap which can cause severe problems 11 148 SUCE The SUCC procedure allows you to determine the successor element to the sepcified scalar constant The invocation takes the form SUCCCelement MISCELLANEOUS FUNCTIONS AND PROCEDURES Page 11 6 where element is a variable identifier or constant of a scalar type Far example PROGRAM VAR Int INTEGER Dat YES NO Y ND BEGIN WRITE Enter integer O READLN Int WRITELN SUCCCInt O Dat YES IF SUCC Dat NO THEN WRITELN YES D END If you enter the number 11 to the program above it prints 12 YES See also Section 11 6 PRED for more information on manipulating scalar types 11 2 SPECIAL TERMINAL DISPLAY PROCEDURES 11 2 1 CHARMODE The CHARMODE procedure allows you to set the terminal of the user of your program into character mode When a terminal is in character mode your program is able to read keyboard input a cha
68. ASP and leave an execution error code in R1 For additional information on ERRORTRAP and a List of execution error codes see section 14 10 Error Handling Procedures and Variables 15 3 CODE RESIDENCY This section discusses the variety of ways in which your routine may appear in memory 15 3 4 Routines PLINKed with LINK Routines which have been linked into a code file with the LINK option must have a final PSB file which is exactly one block in size Such routines are dynamically paged into memory along with Pascal psuedo code They are deleted from memory and reloaded as memory requirements and usage demand They place no burden on available memory when not being used ASSEMBLY LANGUAGE SUBROUTINES Page 15 6 15 5 2 Routines PLINKed without LINK Routines which have been Linked into a code file without the LINK option will be searched for in memory and on disk each time they are called What has been linked into the code file is not the actual routine but rather the name of the PSB file containing that routine see section 4 4 4 If your routine has been loaded before entering AlphaPascal via the LOAD command either into system memory or user memory then that copy of your routine will be used If your routine is not present in memory it will be temporarily loaded in order for it to be executed and then deleted from memory immediately after execution 15 4 OBTAINING MEMORY FOR DATA AREAS When writing an assembly la
69. April 1981 COMPATIBILITY AND CONVERSION Page 3 4 7 Two new keywords have been added to AlphaPascal EXTERNAL and MODULE These words may no Longer be used as identifiers If they do appear in your programs you see an error message Ce g CTRYSCAN VAR PROCEDURE or FUNCTION expected scanning when you compile the programs EXTERNAL allows you to access variables procedures and functions in an external library and allows a file in a multiple file program to access variables procedures and functions in another file See Section 6 7 External Declarations for more information The MODULE keyword designates a file that does not contain the main program portion of the program Modules may contain declaration and definition statements but may not contain the final BEGIN END block That is BEGIN END blocks may only appear in function or procedure definitions if they appear in modules See Section 6 1 Program Declarations for more information The SEGMENT keyword and segment procedures are no longer supported See the discussions of EXTERNAL and MODULE above Remove the SEGMENT keyword from your programs gt Floating point numbers are now three words in length i e 12 digits They used to be two words and could only represent six digits gt You may cali assembly language subroutines from within your Pascal programs For information on writing assembly Language subroutines see Chapter 15 Assembly Langu
70. BLOCKS FILENOTFOUNDO 14 5 3 Function Definition Finally the external function linkage definition is made as follows EXTERNAL FUNCTION SPOOL F P STRING l SW CP INTEGER FRM STRING L W INTEGER SPOOLERROR 14 5 4 The SPOOL Subroutine Call SPOOL via SPOOL CODE zsSPQOL CFILENAME PRINTER SWITCHES COPIES FORMS LPP WIDTH where SPOOLCODE A variable of type SPOOLERROR which gets the completion code shown in the above TYPE declaration If SPOOLCODE is not set to SPOOLED after the call is made then an error of some kind Occurred and the file was not printed FILENAME A string variable or expression that gives the specification of the file you want to print PRINTER A string variable or expression that gives the name of the printer to which you want to send the file If PRINTER is a null string SPOOL uses the default printer SWITCHES An integer variable or expression that specifies various control switches and flags that affect the printing of the file The control switches that SPOOL uses are exactly the same as the switches used by the monitor PRINT command See the AMOS System Commands Reference Sheets in the User s information section of the AM 100 documentation packet for information on PRINT Each switch you can use has a numeric code associated with it see below For example the BANNER switch code is 1 the DELETE switch code is 4 Set control switches by putting the sum of the appropriate switc
71. CF Do you wish to change this Answer Y or N You will probably want to answer N to instruct PLINK to use the same library the file was originally Linked with If you answer Y PLINK asks for the new library New standard library OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 15 Enter the specification of the external library you want to use Now PLINK asks what files you want to link together Just enter the specifications of the module or modules you have re compiled The rest of the modules in the PCF file will be Left alone NOTE If you do change to a new library you will have to re link all modules used in the program and the main program file since the old modules will be incompatible with the new Library See Section 4 5 1 Library Version Checking for more information on program library compatibility PLINK will tell you what new procedures or functions have been Linked in and what old procedures or functions have been kept For example Keeping global func proc ERRCHECK Keeping global func proc PROGRAM Linking global func proc NEWPROC 4 4 4 Linking Assembly Language Subroutines the LINK Option We mentioned briefly above in Section 4 4 1 Linking a New PCF File that you can Link assembly Language subroutine PSB files into your PCF file by specifying the PSB extension when you use PLINK to link the subroutine files into the program For information on such routines see Chapter Lay Assembl
72. E EXTENSION does not change the extension of the file on the disk it only changes the extension of the file specification associated with the file identifier 10 2 6 FILESIZE The FILESIZE function returns the number of disk blocks taken up by the AMOS file associated with the specified file variable You must have previously used the OPEN or LOOKUP procedure on the AMOS file The invocation takes the form FILESIZE file identifier where file identifier is a file variable For example PROGRAM TestFileSize VAR TheFile FILE OF CHAR Counter INTEGER BEGIN TestFileSize gt Counter FSPEC TheFile BIGFIL DAT CREATE TheFile 50 WRITELNC The number of disk blocks is FILESIZE TheFile END TestFileSize First the program above creates the random file BIGFIL DAT then it prints The number of disk blocks is 50 INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 21 10 2 7 FSPEC The FSPEC function performs two main functions it associates the specified file variable with the specified AMOS file and it returns the number of characters in the specified variable or string literal that make up the file specification part The invocation takes the form FSPECCfileridentifier filename default extension where file identifier is a file variable with which you want to associate the AMOS filespec filename gives the name of the AMOS file and default extension gives the extension you want to use i
73. E GETLOCKS JOBUSER LINEMODE LOOKUP MOVELEFT OPEN ORD POWER PWROFTEN READ RESET SCAN SIN SGR STRIP TIME VAL XLOCK AiphaPascal ARCCOSH ARCTANH CONCAT CREATE EOLN ERRORTRAP EXTENSION FSPEC INCHARMODE KILCMD LN MA INPROG MOVER IGHT OPENI PAGE PRED PWROFTWO READLN REWRITE SEEK SINH SQRT SUCC TOD WRITE XMOUNT Page A 12 standard functions and To find out what pages of this book discuss a particular procedure or function refer to the Index ARCSIN CHARMODE COPY CRT ERASE EXIT FACTORIAL GET INSERT LCS LOCATION MARK NEW OPENO PFILE PUT RADSO RELEASE RND SETFILE SIZEOF STDERRORTRAP TAN TRUNC WRITELN For a List of all standard identifiers and reserved words see Section 5 4 Legal Identifiers Changed 30 April 1981 QUICK REFERENCE TO ALPHA PASCAL Page A 11 A 5 2 5 Repetitive Statements WHILE Boolean expression DO statement or REPEAT statement list UNTIL Boolean expression Or FOR variable identifier expression TO expression DO statement or FOR variable identifier 5 expression DOWNTO expression DO statement A 5 2 WITH Statement The WITH DO statement allows you to access record fields as if they were simple variables WITH record variable1 record variable2 record variableN DO statement QUICK REFERENCE TO ALPHA PASCAL A G ALPHA Below is procedures particular Page A 12 PASCAL STANDARD FUNC
74. ECORD variants TCALTMA Too many arguments supplied CCALTXT Preceding argument must be of type TEXT FILE OF CHAR CCALWRMJ Preceding modifier must be of type INTEGER CCALWRT Must be INTEGER REAL CHAR String or pck d arry of chr CSDJNK Junk after constant definition scanning CCSTSGN Only INTEGER and REAL constants may be signed LEXPORX In x OR v x must be of type BOOLEAN CFACCETI In CASE x OF x must be a non REAL scalar type CFACCLTJ In CASE x OF labels must be compatible with x CFACCVTJ In CASE expressions all cases must have compatible types CFACDCS The previous case label has already appeared CFACIFT THEN and ELSE expressions must have compatible types CFACRTL Proc or func too Large split it into smaller pieces CFACSCK In set constructor set elements must be scalars CFACSCT In set constructor all elements must be compatible CGVDFILA Global files must be declared in PROGRAM file GVDFWP x present and x never declared for some x CGVDJNKJ Junk after variable definition scanning LINIESF Empty source file CINILTL First source Line too long truncated to 132 characters CINTPOM PROGRAM or MODULE expected PROGRAM assumed CINTRPR O expected inserting 2 CINISEMJ expected inserting CINISOI or identifier expected inserting LINISOPI s or expected inserting Changed 30 April 1981 ALPHA PASCAL COMPILER ER
75. EOLN 2 The program above keeps reading characters until the user enters a RETURN that is until EOLN is TRUE Then it prints the number of characters in the input string For example a sample run of the program might Look like this e Enter a line of characters NOW I5 THE TIME NOW IS THE TIME number of characters 15 10 4 4 GET and PUT GET and PUT are the two basic file 1 0 procedures You may use GET and PUT on files of any type not just TEXT files 10 1 4 1 GET GET advances the buffer variable to the next file component in doing so it assigns the value of that file component to the buffer variable The invocation takes the form GETCfile identifier INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 6 where file identifier is a file variable If doing a GET moves the buffer J variable past the end of the file then the EOF function returns TRUE and the contents of the buffer variable is undefined So save the contents of the buffer variable into another variable before doing a GET if vou need to access the very Last item in the file 10 1 4 2 PUT PUT writes the value of the buffer variable into the component at the current file position The procedure invocation takes the form PUT fileridentifierd where file identifier is a file variable The EOF function remains TRUE 10 1 4 3 Sample Program Using GET and PUT Below is a very simple program using GET and PUT Notice that we use the OPEN st
76. ERISTICS Page 4 16 NOTE Usually if you modify a module or PSB file you only need to re Link the modified file into the Linked PCF file of which it is a part For example if you changed the file XPUT PSB in our example above you would not need to re link MAINPR and MODULI only XPUT PSB However if you decide to replace a PSB file with a Pascal file of the same name or vice versa you will need to re link all modules that form the PCF file of which that file is apart For example Looking at our example above again if you decide that the file MODULI would be better as an assembly Language file MODUL1 PSB you will need to re Link all of the files that form the complete PCF file MODULI PSB MAINPR and XPUT PS amp 4 4 5 Preventing Backtracing of PCF Files the SMASH Option AlphaPascal allows you to trace the functions and procedures called by a program This is a useful debugging feature when you are developing a program since you can interrupt the program at a trouble spot and see what function or procedure it is in For more information on backtracing see Section 4 5 2 Interrupting a Program However once a program has been finished and tested you may not want users of that program to be able to find out the names of the program functions and procedures which they can ordinarily do by interrupting the execution of the program and backtracing Therefore AlphaPascal provides the linker SMASH option When you Li
77. ERRORTRAP gt PROCEDURE Format VAR X STRING Left Right INTEGER Num REAL VAR Pow REAL BEGIN Procedure Format TF Left gt 11 OR Left lt O THEN ERROR 1 Pow PWROFTEN Left IF ABS Num gt Pow THEN ERRORC1 Value range error Y STR Pow ABSCNum O Right Force leading zeros by adding power of ten and converting to STRING gt DELETECX 1 1 Remove leading 1 gt X 45 TF Num lt 0 THEN CONCAT X ELSE CONCAT X END Format 7 BEGIN Main program Format S 5 2 12 72 Return answer in S gt WRITELN C Format 5 2 12 7 S 2 WRITELNC Result should be 00012 70 END Main program Changed 30 April 1981 CHAPTER 13 STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES This chapter contains descriptions of the standard functions and procedures you can use on data that have been declared as type STRING or packed These functions and procedures have been pre deciared for you For a full List of all functions and procedures refer to Of type CHAR by AlphaPascal Appendix A Quick Reference to AlphaPascal These are the functions and procedures described in this chapter For data of type STRING CONCAT COPY DELETE INSERT LENGTH LCS POS STRIP ucs VAL Concatenates specified strings Copies specified string Cor partial string into another string Deletes specified number of characters from string Inserts specified string or partial string i
78. ES Page 7 19 TYPE Customer RECORD Name STRING SO7 Number INTEGER CASE Car BOOLEAN OF TRUE LicenseNo STRINGC Model STRING 1531 Year INTEGER FALSE 2 O You may omit this Line gt END VAR Query 2 ARRAY 1 200 OF Customer 7 2 8 Painter Type Pascal recognizes two categories of variables static and dynamic Static Variables Static variables are declared in variable declarations which determine their types and identifiers You use these identifiers to refer to the variables Static variables are created when the block in which they are declared is executed and remain in effect until vour program leaves that block Most of the variables shown in this book are static variables They can only be used when you know ahead of time what the storage requirements of your program is going to be Dynamic Variables Dynamic variables are created on demand They do not appear in variable declarations and so cannot be referenced by variable identifiers Instead each dynamic variable of type X has associated with it a value of type X which is called the pointer to X The pointer to X is used to access the corresponding dynamic variable and contains the value of the address of the value The pointer type is declared via the type declaration statement TYPE Identifier base type The symbol identifies a pointer For example TYPE Location INTEGER The declaration above establishes
79. ES Page 15 4 15 2 2 Data Formats This section describes the internal format of each data type Ail data types are aligned on a word boundary unless contained as a packed field 15 2 2 1 CHAR Characters are represented by their ASCII code in a full machine word They are only stored within single bytes of memory when contained in packed arrays or records 15 2 2 2 INTEGER Integers are represented in a single machine word 15 2 2 5 BOOLEAN Booleans are represented by a zero FALSE or one TRUE in a full machine word They are only stored as single bits when contained in packed arrays or records 15 2 2 4 Subranges and Scalar types These are represented in a full machine word unless they appear in a packed array or record in which case they are stored in a field of as many bits as necessary to hold their maximum value User scalar types are numbered starting from zero 15 2 2 5 REAL Reals occupy three words of memory and conform with the format for reals used by the FADD FSUB FMUL FDIV and FCMP machine instructions 15 2 2 6 STRING Strings are represented by a length byte containing 0 255 followed by a sequence of bytes which are used to hold the actual characters of the string d5 d dor Pointers Pointers require a full machine word 15 2 2 8 Sets Sets require one or more words depending upon the size of the set Sets are represented as a bit pattern where a one bit denotes the presence of a set element T
80. F 106 70 46 Upper Case Letter G 107 71 47 Upper Case Letter H 110 72 48 Upper Case Letter I aaa A4 73 49 Upper Case Letter J 112 74 4A Upper Case Letter K 413 d 75 48 Upper Case Letter i L 114 6 4c Upper Case Letter i M 115 7 4p Upper Case Letter N 116 78 4E Upper Case Letter 0 kb 4117 79 4F Upper Case Letter P 120 80 50 Upper Case Letter Q 121 81 51 Upper Case Letter R 122 82 52 Upper Case Letter S 123 83 53 Upper Case Letter T 124 84 54 Upper Case Letter U 125 85 55 Upper Case Letter V 126 86 56 Upper Case Letter W 127 87 57 Upper Case Letter X 130 88 58 Upper Case Letter Y 131 29 59 Upper Case Letter T 132 90 SA Upper Case Letter E 133 91 58 Opening Bracket 134 92 5c Back Slash 3 135 93 5p Closing Bracket 136 94 SE Circumflex E 137 95 SE 1 Underline 140 96 60 Grave Accent a 141 97 i Lower Case Letter b 142 98 62 Lower Case Letter c 143 99 63 Lower Case Letter d 144 100 54 Lower Case Letter e 145 101 65 Lower Case Letter f 146 102 66 Lower Case Letter g 147 103 67 Lower Case Letter h 150 104 68 Lower Case Letter i 151 105 69 Lower Case Letter j 152 106 6A Lower Case Letter k 153 107 68 Lower Case Letter L 154 108 6c Lower
81. File Two INTEGERs followed by STRING INT 12 IsaString Lf you omit the file identifiers WRITE Cexpression List WRITE assumes you want to write to the Dpre declared file QUTPUT the terminal display 10 1 5 4 WRITELN WRITELN outputs a List of expressions to a file or terminal To print a string literal enclose it within single quotation marks You must only use WRITELN with TEXT files WRITELN differs from WRITE in that it writes an end of Line marker carriage return line feed pair after writing the specified data The invocation takes the form WRITELNCFA Le identifier expression iist where file identifier is a file variable and expression list is a list of expressions to be written Separate the WRITELN arguments with commas If you omit the file identifier WRITELNCexpression List INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 10 WRITELN assumes that you want to write to OUTPUT the terminal display You may write just a carriage return line feed to a file or terminal by omitting the expression List WRITELNCfile identifier or WRITELN 10 1 5 5 Formatting Output AlphaPascal uses certain conventions for outputting data STRING data and data of type CHAR are displayed with no Leading spaces Numbers are written differently depending on whether they are REAL or INTEGER AiphaPascal will always print REAL and INTEGER numbers in decimal notation if the number is Less than 12 digits If the
82. For information on how to use these files see Section 4 6 Helpful Command Files 4 1 1 File Extensions Some of the extensions recognized Dy various components of the Pascal programming system are Changed 30 April 1981 OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 3 PAS Pascal source file created by text editora PO1 Pascal intermediate files created by the 2PO2 compiler Not directly executable P03 PCF Pascal code file The executable program file created by the Linker PSB Pascal assembly Language subroutine INC Include files NOTE No PSB files have been included with this release although many of the routines in the standard library are actually Linkedin assembly Language programs If you write your own assembly Language subroutines they must have the PSB extension The advantage in using assembly language programs in combination with your Pascal functions and procedures is that some systems functions can best be performed by an assembly Language program because of speed size or hardware requirements allez File Search Pattern Pascal uses a standard search pattern in looking for those files that it needs For PCF and INC files this pattern is The account you are logged into Your project library account 03 The Pascal Library Account PAS DSKO 7 5 For PRUN PRG this pattern is System memory User memory partition System Library Account SYS DSKO0 1 4J Yo
83. H mad PO Q CHAPTER 8 EXPRESSIONS 8 1 OPERATORS A AA cers BS 8 1 1 Operator Precedence o o onasonan ar 81 8 1 2 Assignment Operator nconosonsnaoono co 8753 8 1 2 1 Modifying Assignment Operators E 8 1 5 Arithmetic Operators nonaroooos 8 1 4 Relational Operators eanoasonesnansosa 8 1 5 Logical Operators cosanasnsoasansasoa 8 1 6 Set Operators veanaesnsnnceas 2 CONSTANTS ozono A 5 VARIABLES annoe nro ss ee E A 5 H E 3 a a E reb KO a de ur ds DYN GAT IF THEN ELSE EXPRESSIONS ancaananaana CASE EXPRESSIONS suanaaaan ee eu em ae i CHAPTER 9 STATEMENTS ASSIGNMENT STATEMENT snaasaon PROCEDURE CALLS s onconnanconanona B i Hd EXIT suawanasaasananaonaaamananaaanuo 4 2 3 4 GOTO STATEMENT escccsucesacen 5 6 f 1 NULL STATEMENT eoa nhan COMPOUND STATEMENT nonsoononos CONDITIONAL STATEMENTS euo onus PIE Es ab Falat IEPSTHEN sat es AG KING ns conuononns 9 7 1 1 IF THEN ELSE pod g a s 2 a P 8 0 9 9 00 0 0 0 WED PUN a ALPHA PASCAL USER S MANUAL Page vi Sara CDASESUR yt os 2 p TE 9 6 9 7 2 1 CASE OF ELSE SR s Id were ium BOR ed d 9 9 8 REPETITIVE STATEMENTS WIN E eam wa X e ein poe EN n cR cu NUR we 9 38 9 8 1 WHILE DO a s v x WES where e e ura fase 9 8 9 8 2 REPEAT UNTIL rn 9 8 3 FOR DO uu A E E mU WA NOT 9 9 929 MITAD mg se alo os ws a la PAREN PRA AE 9 10 CHAPTER 10 IN
84. ILITY AND CONVERSION 3 1 PREVIOUS VERSIONS OF ALPHA PASCAL 5 2 STANDARD PASCAL annansanncace dw E ote nace ae 3 3 MAKING PROGRAMS COMPATIBLE WITH THE NEW ALPHA PASCAL A anales a ae CHAPTER 4 OPERATIMG INSTRUCTIONS AND CHARACTERISTICS amp 1 FILE AND MEMORY REQUIREMENTS 22ose 4 1 1 File ExtensionS o ro Wisin us m ai n amp 1 2 File Search Pattern e 4 1 5 Program Restrictions e iue ids amp 1 4 Memory Requirements r eanovsaononona 4 2 CREATING A PASCAL PROGRAM nunacnuevenauacen 4 5 THE ALPHA PASCAL COMPILER aceononcanroson 4 3 1 The Diagnostic Display nanaosana amp 5 2 Compiler Options s TTE 4 3 2 1 The GOTO Options G and 6 on 4 5 2 2 The Include Option I amp 5 2 5 The List Options SL SL and SL 4 3 2 4 The Page Option SP amp 5 2 5 The Quiet Options Q and 0 waa Page 111 ALPHA PASCAL USER S MANUAL Page iy 4 5 2 6 The Range Check Options CER and BR Seray raa 4 10 4 4 THE ALPHA PASCAL LINKER 2 cacacccuncunccecuce 4 11 4 4 1 Linking a New PCF File cevacuacaccacn 4 12 4 4 2 Replacing a PCF File cecnawuce D 4 15 4 5 5 Updating a PCF File eU e etat a ue sd 4 1 4 4 4 Linking Assembly Language Subroutines the LINK Option Wi aim A RUBUS ae 415 4 4 5 Preventing Backtracing of PCF Files the SMASH Option s etna ea ae 4 16 4 5 THE ALPHA PASCAL RUN TIME PACK
85. Logical operators Logical records LOOKUP os X v oco LOOP Xs s a MAINPROG a s e e MARI ovo owe oo Mathematical function ABS al cae a Oe ARCCOS w mau gt Changed 30 April 19812 bit 3 d d 4 AA ia Co b e i 44 HA P Lb f J Uo Cx i P WA D OR e WORM UP AS o Oe L LA GR OS 1A 00 al bh fo O DOO M AREE Ua ELT Tr m a IN wi gt D Poux d vin A amp 13 5 4 717 14 3 7 22 4 11 an 4 21 12 4 15 6 6 6 14 1 12 4 10 16 10 24 14 2 7 22 12 1 12 43 12 2 us t 147 AA i Lak ow E F nuc e pa o i 11 3 11 5 Page Index 5 ALPHA PASCAL USER S MANUAL r Page Index 6 ARCCOSH 2 ss n mow a 12 3 ARCSIN x qox wow ow vow cw wc Tere ARCSINH soa u on on o n n9 1273 ARCTAN a aa Ax alte o e ETO ARCTANH ma s on no n ew 1273 COS m qnasi E a GOSH Mina o v de Neu em or Sead rete EXPL e rat uel ugs wg Et EXPONENT so ew a a o 1275 FACTORIAL mooo o Teh 1 MEE ES Br COG 26 ea aS ewe et dz ras yk Lena ODD hm Ga e Mee et od ar ce a SVG POWER a s a s so n n o o a a 12u4 PWROFTEN sa mo o awan 125 PWROFTWO 6 wa way 125 RANDOMIZE a oo 12 75 RND X DD iha oe Jew a 31679 ROUND e ov Wow Ae ai an xo 0670 SHIFT nie ov lc wow wow 10 6 DIN a casa LAUS cepi wi ar diez SINH caede seo ole eco uw AE SQR e se ae Uu vw ee uml cw ceca ING36 SORT 2 WG kad maang T256
86. MARK and RELEASE allow you to perform very powerful operations with dynamic variables However they can be dangerous if used unwisely you should be an experienced Pascal programmer before using MARK and RELEASE Changed 30 April 1981 CHAPTER 8 EXPRESSIONS An expression is any combination of operators Constants function calls and variables For example 238 6 x Invoice SQRTCTaxBill 365 This chapter discusses the legal AlphaPascal operators and gives the rules of operator precedence We also talk about some special expression handling abilities of AlphaPascal Bel OPERATORS An operator is a symbol that directs Pascal to perform an action on the elements of an expression For example the addition operator in the expression 344123 tells Pascal to add the numbers 34 and 123 The operator types in Pascal are arithmetic Boolean relational Logical and set Another special operator the assignment operator is used to assign values to variables 8 1 1 Operator Precedence When Pascal sees the various operators in an expression it evaluates the elements in the expression in response to those operators When more than one type of operator appears in one expression Pascal follows a set of rules called operator precedence in determining which operators to act upon first If the precedence of all operators in the expression is the same Pascal evaluates the expression from left to right For example
87. MODULE FIND I NAMREC INC I EMPREC INC3 EXTERNAL FUNCTION SameNames Namel Name2 NameRecord BOOLEAN EXTERNAL VAR EmpFiie EmpFileType RecNum PreviousRecNum INTEGER FUNCTION Find Name NameRecord BOOLEAN Searches for specified record in Empfile Returns true if found leaving file positioned at desired record BEGIN RecNum ControlRecord FirstPataRecord Name LastC 113 PreviousRecNum QO WHILE RecNum lt gt O DO BEGIN SEEK EmpFile RecNum GET EmpFile IF SameNames Name EmpFile Name THEN BEGIN Find zTRUE EXITCFind END PreviousRecNum RecNum RecNum z EmpFile NextDataRecord END Find FALSE END Find CHAPTER 11 MISCELLAMEOUS FUNCTIONS AND PROCEDURES The functions and procedures described in this chapter perform a variety of functions such as allowing your programs to position the cursor on the terminal screen and manipulating dynamic variables The functions and procedures discussed in this chapter are CHR Convert ASCII value to its character representation ORD Returns ordinal number of element in scalar type PRED Returns predecessor i e previous item of scalar type SUCC Returns sucessor isea next item of scalar type KILCMD Abort command file execution NEW Creates new dynamic variable MARK Marks element on the heap RELEASE Releases element on the heap CRT Position screen cursor and enable certain terminal display options CHARMODE Sets terminal i
88. N WRITE C How many records to you wish to use READLN Quantity WHILE Quantity lt 1 OR Quantity gt 100 pO BEGIN WRITE C Please enter a number between 1 and 100 li READLN Quantity END CreateEmployeeFile Quantity END OpenEmpFi le CRT 1 0 3 Clear screen END Introduction PROCEDURE GetName VAR Name NameRecord Note UCS only works on strings and Middle is of type CHAR VAR S STRINGI BEGIN WITH Name DO BEGIN WRITEC Last Name 2 READLN Last UCS Last WRITEC First Name READLN First UCSCFirst WRITE Middle Initial 33 READLN SO UCS SO Middle IF Sz THEN ELSE S 11 END END PROCEDURE GetEmploveeInfo VAR Employee EmpRecord BEGIN WITH Employee DO BEGIN WRITEC How old is Name First READLN Age WRITEC Is Name First Sex 35 IF Yes male THEN Male ELSE Female END END GetEmployeeInfo INPUT OUTPUT FUNCTIONS AND PROCEDURES PROCEDURE ShowEmployeelnfo Employee EmpRecord BEGIN WITH Employee Name DO BEGIN WRITE Last First Middle ds WRITE Age years old WRITELN sex CASE Sex OF Male male Female female ELSE END END PROCEDURE ProcessRequests VAR Options CHAR PROCEDURE ListEmployees VAR CH CHAR Count INTEGER BEGIN Count 5 WRITELN FOR CH s A TO Z po BEGIN RecNum ControlRecord FirstDataRecord CH WHILE RecNum lt gt 0 DO BEGIN SEEK EmpFile RecNum GET EmpF ile ShowEm
89. NCTIONS AND PROCEDURES l ll rures A 12 APPENDIX B THE ASCII CHARACTER SET APPENDIX C ALPHA PASCAL COMPILER ERROR MESSAGES INDEX CHAPTER 1 INTRODUCTION This book is a reference manual for the AlphaPascal programming system We realize that some of you may be experienced Pascal programmers while others may never have seen a Pascal program before Therefore t suit the wide range of interests and backgrounds our readers are likely to have we have tried to organize this book so that you can easily find the information that you need without spending unnecessary time on chapters that contain information that you already know or that is not important to you For information on the organization of this book see Section 1 1 below Because there are so many excellent books available that teach you hew to program in Pascal we have not attempted to do so in this book For a list of some of the books that we found helpful see Section 1 2 Pascal Bibliography However our intention is to provide a detailed enough description of AlphaPascal that an experienced computer programmer who is unfamiliar with Pascal can get some idea of how to write Pascal programs The major purpose of the book is threefold 1 To describe this implementation of AlphaPascal 2 To discuss how this implementation differs from previous versions of AlphaPascal and from the standard Pascal as set forth in the Pascal User Manual and Report by Jensen and Wirth a
90. NOMETRIC FUNCTIONS 12 1 1 COS Cosine trigonometric function Accepts a REAL or INTEGER argument and returns a REAL result Argument must be in radians 12 1 2 SINO Sine trigonometric function Accepts a REAL or INTEGER argument and returns a REAL result 12 1 3 TANOO Tangent trigonometric function Accepts a REAL or INTEGER argument and returns a REAL result Changed 30 April 1981 MATHEMATICAL FUNCTIONS Page 12 2 12 1 4 ARCCOSIX Arc cosine trigonometric function Computes the inverse cosine function See COS above Accepts a REAL or INTEGER argument and returns a REAL result X must be greater than or equal to 1 and less than or equal to 1 12 1 5 ARCSINOO Arc sine function Computes the inverse sine function See SIN above Accepts a REAL or INTEGER argument and returns a REAL result X must be greater than or equal to 1 and less than or equal to 1 12 1 6 ARCTAN X Arc tangent trigonometric function Computes the inverse tangent function See TAN above Accepts a REAL or INTEGER argument and returns a REAL result 12 2 HYPERBOLIC TRIGONOMETRIC FUNCTIONS 12 2 1 C0SHOO Hyperbolic cosine trigonometric function Accepts a REAL or INTEGER argument and returns a REAL result Argument must be in radians 12 2 2 SINHOO Hyperbolic sine trigonometric function Accepts a REAL or INTEGER argument and returns a REAL result 12 2 3 TANH X Hyperbolic tangent trigonometric function Accepts a
91. OARD have associated with them special AMOS file specifications TTY TTY and KBD TTY specifies your terminal For example if you give TTY as the file specification to the compiler Listing option L the compiler sends the Listing to vour terminal display The KBD specification is equivalent to the TTY specification except that it prevents input from being echoed to INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 15 the terminal display if the terminal is in Charmode See Section 11 2 1 Charmode for information on charmade NOTE The normal end of Line separator is a carriage return Normally the monitor appends a Line feed character onto the end of a carriage return If you are in Charmode and are using the KBD device the monitor does not automatically append a line feed onto the end of a carriage return Therefore if you are using KBD in Charmode you should use GETs and PUTs to retrieve data since READ has a one character lookahead buffer which will cause it to wait on the Line feed when it encounters a carriage return 10 2 1 1 Random Files Random file blocks are allocated contiguously on the disk and access to such a file is random that is by computing an offset the system can access any one record in that file without accessing any other record Random file blocks are 512 bytes To create a random file you will use the CREATE procedure One advantage in using a random file is that access to tha
92. ONCAT LOSH CREATE EOF EOLN ERRORINFO ERRORTRAP EXPONENT EXTENSION FILESIZE FSPEC GETLOCKS IDSEARCH JOBDEV JOBUSER LENGTH LINEMODE LOG LOOKUP MEMAVA IL MOVELEFT ODD OPEN OPENR ORD POS POWER PVIRT PWROFTEN RANDOMIZE RDC RDS READ RENAME RESET RND ROUND SETFILE SHIFT SIZEOF SPL SQRT STDERRORTRAP SUCC TAN TOD TREESEARCH VAL WIN WRT WRITE WRS XERRORTRAP XMOUNT block structured Language See Figure 5 1 below Page 5 7 ARCSIN CHARMODE COPY CRT ERASE EXIT FACTORIAL GET INCHARMODE KILCMD LN MAINPROG MOVERTGHT OPENI PAGE PRED PWROFTWO RDI READLN REWRITE SCAN SIN SPOOL STR TANH TRUNC WRB WRITELN XL OCK program falls Each Block in Pascal the diagram represents some procedure or function within the program What happens if for example a variable is declared in the main program and then re declared in a procedure called by main program Which declaration is valid This problem is resolved by defining the scope of the identifier that is by defining the area of a declaration of an identifier is valid The scope it is defined and any enclosed blocks which do not redefine it an identifier in the same block as use of an identifier declared in an outer block is called a reference the non local reference Changed 30 April 1987 its program declaration for which the of an identifier is the program procedure or function in which The use af
93. PUT OUTPUT FUNCTIONS AND PROCEDURES 10 1 BASIC FUNCTIONS AND PROCEDURES acconvacenee 101 10 1 1 The File WINdOW a ta su 10 3 10 1 2 EOF End of file Function eae 1073 10 1 3 EOLN End of Line Function 10 4 IUXTA GET PUE aia ous a rada 21 10 5 WASTE GET ara TES TO ee PU A e 10 6 10 1 4 3 Sample Program Using BET and PUT cercada nex e 10 6 10 1 5 READ READLN WRITE and WRITELN 10 7 10 1 25 3 READ ca hwa kaaa EM 10 7 esa READER Savas ee Excess des 1021 53 WRITE aria das tw 10 1 5 4 WRITELN 2no ooonrocos re ee 10 9 10 1 5 5 Formatting Output s 10 10 10 1 6 PAGE MUR ARCA Ra RU pis X KWAN s Red 10 13 TO 27 RESET cs WR uM m ur MIR AUS sig 10 13 1041 8 REWRITE ll alaba so 10 13 10 2 SPECIAL FUNCTIONS AND PROCEDURES EUR ILE C DOO aca sequ ON 10 14 10 2 1 Information on AMOS Files 10 14 10 2 1 1 Random Files wxwsses m5 10 2 1 2 Sequential Files s 10 15 10 2 1 3 Logical Records 10 16 10 2 1 4 Opening and Setting Up Files 10 16 FUE CLOSE Sulis sa saaaanaaaaonananaxaaon 1017 Mogae CREATE ac tro TOTO Mee ah ERASE a VOTA Mitos EXTENSI N ius a a emis E RR sono 10 19 10 267 FILESIZE aaa MO Sel TR Ru VESPERE arado ios 10 21 TUsQes GETPIEE eras 4enen acuueenonctenean 10 22 T0 2 9 JOBDEV ra retesaonssoneo nxa 10 23 10 2 10 JOBUSER ada sancsuonpussana ai e s 10 24 Wes EOOR o a roland ano 10 24 10 2 12 OPEN nanaon shsurt
94. R Number X Y STR CNumber X where X specifies a minimum field width and Y specifies the number of digits to write after the decimal point If the number is Larger than the field specified by X PASCAL does not truncate the number but prints the number using the necessary number of digit positions Changed 30 April 1981 MATHEMATICAL FUNCTIONS l i Page 12 7 If Number is INTEGER you may not specify Y These two variations of STR perform formatting in exactly the same way as WRITE and WRITELN except that they do not generate a leading space for positive numbers For example given the REAL data 123 44 WRITELNCSTR 123 44 10 4 3 returns the string 123 4400 where the number is right justified in a field of ten blanks and four digits are written to the right of the decimal point 12 5 18 TRUNCOO Truncates X Accepts REAL argument returns INTEGER result For example TRUNC 26 3 returns the integer 24 12 4 SAMPLE PROGRAM TO PAD A NUMBER WITH LEADING ZEROS Below is a useful procedure to pad a number with Leading zeros along with a sample program that makes use of it PROGRAM Format VAR S STRING Lic f The procedure call Format String Left Right Number formats the number with Left zero filled digits before the decimal point and Right zero filled digits after the decimal point A trailing space or minus sign is added to indicate the sign of the number Illegal arguments generate an error to
95. RACTIVE e g TYPE INTERACTIVE TEXTO For information on type FILE see Section 7 2 6 below DATA TYPES Page 7 12 7 2 5 SET Sets give you a very efficient way ot handling certain kinds of information Although they are not exactly analogous you might think of sets as a kind of packed Boolean array The use of sets allows complex logical expressions to be written concisely and also gives a more flexible way of performing Logical tests For example instead of the cumbersome statement IF Character A OR Character B OR Character C OR Character Dn OR Character E THEN Flag TRUE using sets you can simply say IF Character IN A E THEN Flag TRUE To define a set type use the type declaration statement Every element of the set must be of the same type and that type may not be structured You must specify the name of the set data type and the base type of that set TYPE Identifier SET OF base type For example TYPE Player SET OF 1 5 Once you have defined the set you can now declare a variable of that type VAR Piece Player which can assume one or more of the values of that set Pascal also allows a shorthand declaration VAR Piece SET OF 1 5 The symbol C J is the set constructor operator It takes a List of expressions of the form lCexpressionl Lexpression expression For example given that Y is of type SET the following is a valid assignment stat
96. RAM BubbleSort An AtphaPascal program may consist of more than one file You can compile these files separately then using PLINK you can Link them together into one program Of the files that you are going to link together only one may be a main program file You tell the Linker which files are not the main program file by including an external program declaration at the front of those files This declaration tells the Linker that the file is not the main program that it is in effect an external file to the main program The declaration takes the form MODULE module name where module name identifies the non program file and does not need to be the same as the name of the main program or MODULE If a file does not contain the main program there are some restrictions on the elements that 3t can contain For information on the format of a non program file see Section 5 1 Program Structure 5 2 LABEL DECLARATIONS if vou want to transfer control to a particular section of a program you must label that section with a statement label Labels are unsigned integers from 0 to 32767 and must be declared in a label declaration statement The label declaration statement takes this form LABEL one or more numbers separated by commas For example if we want to use the labels 25 and 100 in a program the declaration looks like LABEL 25 100 Labeis appear in the program in front of the statement they designate and end
97. RAY 1 503 OF INTEGER END VAR X ARRAY 1 203 OF Rec you would have to perform a great many record moves a slow and inefficient process If you instead use pointers VAR X ARRAY 1 201 OF Rec you only need to sort pointers which is much faster Here is a very smali sample of the use of pointers VAR X Y INTEGER BEGIN NEWOO Yi x 8 X 5 WRITE X Y r 67 WRITE WRITE CX Note X and Y are pointing to the same Location so output will be 5 8 6 gt END A Linked List is one example of a useful data structure you can build with pointers You might also consider building doubly Linked Lists trees queues etc Let s take a look at the linked List and see why it is SO useful and how to build one DATA TYPES l i Page 7 21 Each element of a linked list contains 1 data and 2 a pointer to the next element of the List To change the order of the elements in the list therefore you only have to change the pointers not the elements themselves E Let s say that you have a sorted array of integers 1f you add another number to the array you must sort the entire array to get the elements back into the proper order If however the numbers are stored as a Linked List adding a new number just entails changing two pointers in the list For examples List 23 MH 32 HA 6 PA A etc NewList EN etc 40 To delete an element of the list you only need to Link around it Declar
98. READ UNITWRITE UNITWAIT UNITBUSY UNITCLEAR GOTOXY Refer to Section 11 2 2 CRT for information on cursor positioning HALT IORESULT INTERACTIVE files PROGRAM the main program may not be called recursively You should be aware of these changes to the standard procedures t 2 RESET and REWRITE accept only one argument a variable of type FILE You may not specify a filename after that argument The file type INTERACTIVE is no longer supported or needed replace it with the standard file type TEXT in earlier versions of AlphaPascal CLOSE took an option as an argument in addition to a variable of type FILE it now accepts only a single argument a variable of type FILE When you use the EXIT statement to exit a program you must supply the PROGRAM keyword as the argument not the program name That is EXITCPROGRAM is valid but EXIT NewProgram is not You may however exit a procedure or function by giving the name of that procedure or function e g EXIT EvalErrord WRITE and WRITELN do not accept a Boolean variable as an argument That is if NewFile is a Boolean variable which evaluates to TRUE WRITELN NewFile does not print TRUE but instead generates an error COMPATIBILITY AND CONVERSION Page 3 6 5 2 STANDARD PASCAL The standard Pascal is described by Jensen and Wirth in the Pascal User s Manual and Report Second Edition AlphaPascal differs from this standard in several ways
99. REAL or INTEGER argument and returns a REAL result Changed 30 April 1981 MATHEMATICAL FUNCTIONS Page 12 3 12 2 4 ARCCOSH X Hyperbolic arc cosine trigonometric function Accepts a REAL or INTEGER argument and returns a REAL result See ARCCOS above X must be greater than or equal to 1 12 2 5 ARCSINH X Hyperbolic arc sine trigonometric function Accepts a REAL or INTEGER argument and returns a REAL result See ARCSIN above 12 2 6 ARCTANH QO Hyperbolic arc tangent trigonometric function Accepts a REAL or INTEGER argument and returns a REAL result See ARCTAN above The absolute value of X must be less than 1 12 3 MISCELLANEOUS MATHEMATICAL FUNCTIONS 12 3 1 ABSOO Computes the absolute value of the argument Accepts one INTEGER or REAL argument and returns an INTEGER or REAL result For examples WRITELNCABS 32 12322 displays the answer 32 125 12 3 2 EXPOD Exponential function Computes e to the X power where e is the base of natural logarithms Accepts a REAL or INTEGER argument returns REAL result Changed 30 April 1981 MATHEMATICAL FUNCTIONS Page 12 4 12 3 3 EXPONENT OO Computes K such that X J 2 K where J is greater than or equal to a5 and less than 1 Accepts a REAL argument 12 3 4 FACTORIAL X Computes the factorial of X Accepts a REAL argument returns a REAL result For example FACTORIAL 6 0 returns 720 720 6 5 4 3k2Xk1 12 3 5 LNOO Co
100. RETURN To what file REMOTE C Now Transfer asks Using what AMOS file Enter a valid AMOS file specification For example DSK1 CONVRT PAS IMPORTANT NOTE You must make sure that this file does not already exist if it does the UCSD AlphaPascal system will not do the transfer and will make the accessed drive inaccessible to you that is it will declare that drive off line until you exit or re enter Pascal d Now Transfer asks CONVRT PAS mode T ext I mage Enter an upper case T followed by a RETURN e Now transfer begins to copy ROMAN TEXT into the AMOS file DSK1 CONVRT PAS When Transfer is done you see SCR ROMAN TEXT transferred to REMOTE You may now use the text editor VUE to modify the AMOS file that contains your program NOTE If your file is too large Transfer may ask for additional AMOS file specifications When you are finally finished you will need to append all such files into a single file using the AMOS APPEND command Here is List of things to check when converting your old programs to current AlphaPascal format Ng Make sure that you da not use the reserved words EXTERNAL or MODULE as identifiers Check the List of standard identifiers in Section 5 4 2 Standard identifiers to make sure that you do not redefine any identifiers that designate functions or procedures you need by including them in global declarations COMPATIBILITY AND CONVERSION Page 3 9 3 Remove any in
101. RITEC and PFILE USserSpeci WRITELN WRITELN WRITELNC Both of your data files must be on the same WRITELN device and unit we are moving them both to DSK0 5 SETFILE Mai lLabel RADSOC DSK RADSOC O Fi lea FileB Ext Proj Prog SETFILE CAddresses RADSQC DSK O RADSOC O D FileAT FileB1 Extt Proj1 Prog1 END WRITES Your files are O PFILE UserSpec WRITEC and PFILECUserSpect END Main Program 3 10 2 9 JOBDEV The JOBDEV function takes two INTEGER variable arguments The invocation takes the form JOBDEV Dev Unit JOBDEV returns in Dev the device you are currently Logged inte in RADSO form and returns in Unit the device unit you are currently Logged into Cin INTEGER form INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 24 10 2 10 JOBUSER The JOBUSER function takes two INTEGER variable arguments The invocation takes the form JOBUSER Project Programmer It returns in Project the project number in decimal you are logged into and returns in Programmer the programmer number in decimal you are Logged into Ki 10 2 11 Lookup The LOOKUP function returns a TRUE or a FALSE depending on whether the specified file exists The invocation takes the form LOOKUP file identifier where file identifier is the file variable associated with the AMOS file you are looking for Since several file procedures generate an error if the file specified to them already exists e g OPENO CREATE
102. ROR MESSAGES Page C 5 CLADERR CLADP CK CLELDDCI CMPATBGI CPRDAFLI CPRDDDFJ CPRDDDPI CPRDENRI CPROFTMI CPRDLPX CPRONSTI CPROPDF CPRDPRFJ LPRDPRPJ CPRDSSPI CSCNINS CSCNMISJ CSELATOJ CSELERRI CSELFOP CSELIXT CSELNIS CSELNSF SELRTO CSELSTF LSELSXOJ CSTDUDFI CSIDWRCI CSMPNUMJ LSTMBIDj STMCSDJ CSTMCSTI STMbOWJ CSTMEWIJ LSTMFFK CSTMFFTI Changed Compiler error in LOADADDRESS xxx You should never see this error message Please report it and the circumstances under which you saw it to Alpha Micro Packed variables may not be used in this context Label already declared in this scope Maximum string size is 255 Only formal VAR FILE parameters are permitted Function or procedure already declared forward Parameter list must only appear in FORWARD declaration a result type identifier gt expected assumed missing Function type not compatible with forward declaration For information on forward declarations see Chapter 6 NG expected assumed missing Procedure function declarations nested too deeply Function or procedure previously defined Previously declared a function in same scope Previously declared a procedure in same scope Function must be of scalar subrange or pointer type Giving up scan inserting xxx Giving up scan xxx assumed missing In xiy or x b v x or xL 3 must be of ARRAY type Compiler error in SELECT You should n
103. RRAY 1 1000 OF CHAR you could cause LongLine to be a packed array by saying VAR LongLine PACKED ARRAY 1 1000 OF CHAR QUICK REFERENCE TO ALPHA PASCAL Page A 5 The structured data types are A 3 2 1 STRING STRING data is a group of characters You may optionally specify a maximum Length by following the keyword STRING with square brackets enclosing the number e g STRING 23J A 5 2 2 Arrays ARRAY Lindexi type index2 type indexN typel OF component type A 3 2 5 Sets SET OF element type A 3 2 amp File Type FILE OF element type or TEXT This is the same as FILE OF CHARY A 5 2 5 Record Type RECORD field list END where field List is of the form field identifier field identifierN fieldi typel fieid identifier aap fielde identifierN field2 type2 field identifier field identifierN fieldN typeN The field List may also contain a variant part which implies that the information in that field may vary as to type The variant part takes this form QUICK REFERENCE TO ALPHA PASCAL i Page A 6 CASE field type OF case label case label field List1 case Label case label field list2 case Label aap case label fieid ListN or CASE case field identifier field type OF case label case label field list1 case Label case label s fieldelist2 IE case label case label field ListN A 3 2 6 Pointer Data Types Th
104. RecNum PUTCEmpFile a E END Add PROCEDURE CreateEmployeeFile Size INTEGER fCreate Recreate Employee File with specified number of employee records VAR X SizelinBlocks INTEGER CH CHAR BEGIN SizelnBlocks 1 Size 1 DIV 512 DIV SIZEOF CEmpRecord X im FSPECCEmpFile EMPFIL DAT 2 CLOSE EmpFile Close file if it is open ERASE EmpFile Erase file if it already exists CREATE EmpFile SizeInBlocks OPENR EmpFile ControlRecord FirstUnusedRecord 1 FOR CH z A TO Z DO ControlRecord FirstDataRecord CH 0 EmpFile ControlRecord PUT EmpFile FOR X s 1 TO Size 1 DO BEGIN EmpFile NextUnusedRecord X 1 PUT CEmpFile as END EmpFite NextUnusedRecord 0 PUT EmpFile2 CLOSE CEmpFile END CreateEmployeeFile PROCEDURE OpenEmpFile BEGIN OPEN CEmpF ile EMPFIL RANDONMD ControlRecord EmpFile END FUNCTION Yes Message STRING BOOLEAN VAR Answers STRING BEGIN WRITE Message READLN Answer LCS Answer IF Answer y OR Answer yes THEN Yes TRUE ELSE IF Answer n OR Answer 7 no THEN Yes FALSE ELSE Yes Yes Please answer yes or noz END Yes INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 35 PROCEDURE Introduction VAR Quantity INTEGER BEGIN CRT 1 00 Clear Screen WRITELNC AlphaPascal Random File Demonstration WRITELN WRITELN IF Yes Do you wish to re create employee file THEN BEGI
105. S file specifications and not the internal names of your programs or modules each specification must contain a six character or less file name that designates an AMOS disk file NOTE Although you will usuatly be Linking together compiled Pascal files you may also want to use PSB Pascal assembly Language subroutine files To tell AtphaPascal that a file is an assembly Language subroutine rather than a Pascal program file you will specify the PSB extension For example File 1 MODUL 1 File 2 MAINPR RET File 2 INPUT PSB RET File 3 ANYCN PSB LINK RET File 4 RET The example above shows us Linking together a main program file MAINPR a module file MODULI an assembly Language subroutine file reference INPUT PSB and an assembly Language subroutine ANYCN PSB For a discussion of how these PSB files are Linked in see Section 4 4 4 Linking Assembly Language Subroutines the LINK Option For information on assembly Language subroutines see Chapter 15 Assembly Language Subroutines 4 4 2 Replacing a PCF File If the VALIO PCF file that we specified as code file already exists PLINK knows that we want to either update or replace the file Therefore after it asks for the code file PLINK asks Do you wish to 1 replace or 2 update VALID PCF To replace the file enter a 1 PLINK now Says OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 14 Creating new code file VALID PCF It asks which extern
106. SEMBLY LANGUAGE SUBROUTINES In AlphaPascal there is no distinction between calling an assembly language function or procedure and calling a Pascal function or procedure which occurs in a separately compiled module Modules were discussed in Section Du wa Section 4 4 4 describes how to Link an assembly Language subroutine into a program during the PLINK process Instead of Linking output files from the compiler you Link a PRG file with an extension of PSB which contains code for a single function or procedure The name of the PSB file must be the first six Letters of the name to be used for calling the assembly Language routine When specifying the file to PLINK you must of course specify the full name of the procedure or function contained in the PSB file otherwise PLINK would not know the full name you wish to use for it ASSEMBLY LANGUAGE SUBROUTINES Page 15 2 For example if you code in assembly Language a procedure that displays a menu the procedure name might be MENUDISP The disk file containing that routine must then be called MENUDI When you specify the file to PLINK though you use the full eight character name of the procedure For example File 1 MENUDISP PSB LINK 15 2 ARGUMENT PASSING CONVENTIONS Your assembly language routine must work with two stacks One of these stacks is the familar SP stack The other is a data stack used by AlphaPascal for passing arguments and recieving results The data stack is indexe
107. STARTED Page 2 6 Of course there are many more VUE editing commands that we won t discuss here You can for example erase characters a word at a time insert entire new Lines of text search for particular groups of characters or move the cursor a word at a time For more information on using VUE see the AlphaVUE User s Manual DWM 00100 15 When the program is entered correctly you are ready to leave VUE Type an Escape The screen clears and the cursor is now positioned next to the VUE prompt symbol gt You are now in command mode Type an F followed by a RETURN This tells VUE that you are finished it therefore writes your file SALARY PAS out to the disk Next you see the AMOS prompt symbol a dot which telis you that you have exited VUE and are now back at AMOS command level Here is a summary of the keys that you will use the most when editing programs with VUE RETURN End each line with a carriage return symbol by pressing the RETURN key sometimes Labeled RET CR or CARRIAGE RETURN ESC To change from editing mode to command mode and back again type an Escape by pressing the ESC key sometimes labeled ALT MODE or ESCAPE CONTROL Most of the VUE commands are control characters To type a control character hold down the CONTROL key sometimes labeled CTRL and type the appropriate character For example to type a Control C hold down the CONTROL key qu while you type a C RUB To delete a single
108. Strip gt Source 25 characters s WRITELN Before stripping out 1533 STRIP Source WRITELNC After stripping Source END TestStrip The program above prints Before stripping 25 characters J After stripping 25 characters 13 1 9 UCS The UCS procedure converts Lower case characters in a specified string to upper case The procedure invocation takes the form UCSCSourceString where SourceString must be a string variable For example PROGRAM TestUCS VAR Title STRINGESOJ BEGIN TestUCS 3 Title fAm0us comPUters i HAve knOWn ucS Titled WRITELNC Converted title is Title END TestUCS 3 The program above prints Converted title is FAMOUS COMPUTERS I HAVE KNOWN STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 6a 13 1 10 VAL The VAL procedure converts a string to a REAL number The invocation takes the form 2 VAL SourceString where SourceString is a string variable that you want to convert to a number For example PROGRAM TestVAL VAR Price STRING Total REAL BEGIN TestVAL gt WRITE Enter price of object rs READLN Price IF POS C Price O THEN WRITELN The price is in whole doitars 3 Total VAL Price WRITELNC With 6 tax the price is Total 1 06 8 2 END TestVAL 3 The program above uses a string function POS on the string Price it then converts Price to a REAL number Total so that it can
109. TIBILITY AND CONVERSION Page 3 3 These operators tell the compiler to modify instead of replace the value of the variable on the left of the assignment operator with the value of the expression on the right of the operator For example in the case of the adding assignment operator X 1 tells the compiler to let X assume the value of X 1 For more information on these operators see Section 8 1 2 1 Modifying Assignment Operators Operator precedence has been changed to make it more compatible with operator precedence in other Language processors on the Alpha Micro system The relational operators have been made of higher precedence than the Boolean operators See Section 8 1 1 Operator Precedence for more information AlphaPascal allows you to label BEGIN END blocks by following the BEGIN and END keywords with a colon followed by an indentifier These labels allow you to tell the compiler which BEGINs and ENDs should match If the structure of your program is such that they do not match the compiler will tell you so E For exampie BEGIN Block1 BEGIN Block2 END Block2 Li END Block1 The compiler checks these Labels to make sure that the designated pairs of SEGIN END keywords are indeed properly matched For example the following program would cause an error because the BEGIN END blocks are not properiy nested BEGIN Block BEGIN Block2 a END Block END Block2 Changed 30
110. TIONS AND PROCEDURES an alphabetic List of all AlphaPascal standard functions and that you may use To find out what pages of this book discuss a procedure or function refer to the Index ABS ARCCOS ARCCOSH ARCSIN ARCS INH ARCTAN ARCTANH CHARMODE CHR CLOSE CONCAT COPY COS COSH CREATE CRT DELETE EQF EOLN ERASE ERROR ERRORINFO ERRORTRAP EXIT EXP EXPONENT EXTENSION FACTORIAL FILLCHAR FILESIZE FSPEC GET GETFILE GETLOCKS INCHARMODE INSERT JOBDEV JOBUSER KILCMD LCS LENGTH LINEMODE LN LOCATION 1 06 LOOKUP MATNPROG MARK MEMAVA IL MOVELEFT MOVERIGHT NEW ODD OPEN OPENT GOPENO OPENR ORD PAGE PFILE POS POWER PRED PUT PVIRT PWROFTEN PWROFTWO RAD5O READ READLN RELEASE RENAME RESET REWRITE ROUND SCAN SEEK SETFILE SHIFT SIN S INH SIZEOF SPOOL SGR SQRT STDERRORTRAP STRIP Succ TAN TANH TIME TOD TRUNC ucs WRITE WRITELN XEQERR XLOCK XMOUNT For Legal Identifiers a list of all standard identifiers and reserved words see Section 5 4 ng APPENDIX B THE ASCII CHARACTER SET The next few pages contain charts that list the complete ASCII character set We provide the octal decimal and hexadecimal representations of the ASCII values Note that the first 32 characters are non printing Control characters THE ASCII CHARACTER SET Page 8 2 THE CONTROL CHARACTERS Cum cem ceu we ep ce can io ane em em cem em mum mm ee nit cite IA ah eer etin regm Tes oam ARE UI TN cord uem anm cem eure a
111. Then it tells CMPILR that you want the diagnostic file to be displayed on the screen NOTE If an error occurs while you are using one of these command files for example if your program contains an error or if AMOS cannot find the specified file AlphaPascal stops execution of the command file After you clear up the problem you can then use the command file again The command files we have provided are DSKO PC DO 2 2 Pascal compile DSKO PL DOL2 23 Pascal link DSK PCL DOL 2 21 Pascal compile and link DSK PCU DOL2 2 Pascal compile and update DSK PU DOF 2 23 Pascal update Remember that these command files do not cover all cases of compiling and Linking files If after you read these descriptions you realize that the file will not do exactly what you need you will have to run CMPILR and PLINK yourself to perform the actions you want 4 6 1 Compiling a Single File PC DO To use the PC file enter PC followed by the name of the file that contains the program you want to compile Then type a RETURN For example PC DRWLIN OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 21 CMPILR compiles the file DRWLIN PAS into the files DRWLIN POT DRWLIN PO2 and DRWLIN POS 4 6 2 Linking a Single File C PL DO To use the PL file enter PL followed by the name of the file that you want to Link For example PL DRWLIN PLINK now Links the files DRWLIN POT DRWLIN PO2 and DRWLIN PO3 together into DRWLIN PCF Before yo
112. UNTIL statement takes this form REPEAT statement list UNTIL Boolean expression STATEMENTS Page 9 9 where statement list may be series of statements separated by semicolons and expression evaluates to TRUE or FALSE For examples PROGRAM VAR Number INTEGER Error BOOLEAN BEGIN Main program Error FALSE REPEAT fares WRITEC Enter an integer divisible by 3 da READLN Number IF Number MOD 3 O THEN penan WRITELN Correct Try another ELSE Error TRUE UNTIL Error WRITELN Incorrect End of exercise END Main Program 3 Because the REPEAT UNTIL keywords appear at the beginning and end of the Loop making it clear where the beginning and end of the Loop are we do not have to include the BEGIN END keywords after the REPEAT keyword however you may do so if you wish A REPEAT Loop will always be executed at least once 9 823 FOR DO The FOR DO statement allows you to execute 4 given statement or group of statements a specific number of times A FOR DO Loop is executed for every value of the control variable from some starting value up to and including some terminal value A control variable must not be of type REAL The FOR DO statement takes this form FOR Variable identifier expression TO expression DO statement For example PROGRAM VAR Counter INTEGER BEGIN Main Program 3 WRITELNC The square roots of the integers 1 to 10 are 2 WRITELN FOR Coun
113. URES Page 10 27 10 2 18 RENAME The RENAME procedure allows you to rename an AMOS file The invocation takes the form RENAMECfilLle identifier newnameJ where file identifier is a file variable associated with the AMOS file you want to rename and newname is a string variable or a string Literal For example if the AMOS file CURRNT DAT is associated with the file identifier AccountsFilez RENAME CAccountsFile BACKUP LST 2 renames the AMOS file CURRNT DAT to BACKUP LST By varying the fields you supply to RENAME you can rename just the extension just the filename or both For example if the AMOS file OLDDAT DAT is associated with the file identifier MailBox RENAME Ma1lBox BAK 2 renames OLDDAT DAT to OLDDAT BAK and RENAME Mai LBox ARCHIV renames OLDDAT DAT to ARCHIV DAT 10 2 19 SEEK The SEEK procedure allows you to position a file pointer to a specific record in a random file for file 1 0 The invocation takes the form SEEK Cfile identifier recardnum where file identifier is a file variable associated with the random file we want to access and recordnum is an integer variable or constant that specifies the number of the record to access The first record 1s record 80 REMEMBER SEEK does not input a record into the buffer variable it just positions the file pointer 10 2 20 SETFILE SETFILE takes the same arguments as GETFILE but it puts information into the file specification
114. Version stamp a s s a a 4 VUE Soca iat a as w E NHILE DO a 2o oco 278 WITH DO a a w va s es 2 10 WRITE c4 God Oe ave ee ws ORD WRITELN a u a w o x9 wow a TO Writing an external Library a 316 4 XERROTRAP a a a a a soa a so e s a 14 16 XLOCK s s a sono s a roa aoa noa a 145 XLOCK SYS e so 9 300 v 146 XMOUNT ee no a o n n n 149 Changed 30 April 1981
115. a dw ASG gi EE s VALS Gi cet ar iow AA cw Raw won ow cC dora String literal eas sa 3717 O74 String notation s soe s s s a 5 10 Strings e a ce BEA STRIB a a a a NGO Structured data type uo a 7 1 6 Subrange data type as s s s woo 7 76 subscPTDt x 0 a SB Subset operator s a a a 876 Teg 8 6 4 SUCE MA e Te as ates UR NG 2p Pra 11 5 Superset operator e e wan e System queue s a aan x o 4 6 TAN At pa Rude x ud nw le Uc Sw hen EAN xTM Terminal display a m s a a e 4 9 Terminal screen handiing 311 7 TEXT ak CU a a e C S TIME uw Sk wie cw ha m Um Kai x NG IM row aea re e ura doge e EIS TRUE uw dp cats an ues ed dade ES Changed 30 April 1981 ALPHA PASCAL USER S MANUAL P Page Index 10 TRUNE o a s e so oo ara 1207 TINS Ra a a we deu 10 14 Type declaration camo O74 HOS uc d be Tae he bah aie cwm Se RA Xov RS Unmounting a disk s s s a a 1479 Updating a single module a a 4 21 User defined data type e a 75 User defined ERRORTRAP a a a a 14 12 User defined functions a 676 User defined subrange s e s a a a 7 6 VALo a aa er X ee cw a a a a Um o nOA Value parameter s a es a s 45 3 Value parameters 6 12 WAR m sa ls ee aa om ow oc o OT Variable declaration a a 2 Variables s m s sea a auas T Variant xo ew a 7 Version number e a s s ea amp
116. a pointer type Location whose pointer variables will point to variables of type RECORD To use the pointer type we must declare variables VAR NewNumber Location NewNumber is a pointer variable that is associated with an integer value An identifier followed by the pointer symbol designates the actual value being pointed to Therefore NewNumber is the actual integer value being pointed to by NewNumber DATA TYPES Page 7 20 Now to actually use the data types we have defined we must use the NEW function to allocate the dynamic variable NEW NewNumber z creates an unnamed variable of type INTEGER and stores the pointer to it in NewNumber To access the new pointer we reference it as NewNumber See Section 11 1 4 NEW for information on NEW AlphaPascal also uses two functions called MARK and RELEASE for manipulating pointer data see Sections 11 1 5 MARK and 11 1 7 RELEASE Pascal contains a special pointer constant that indicates that a pointer is not pointing to anything NIL This is useful for indicating special conditions such as the end of a list For example EndingNode NIL The use of pointers gives the Pascal programmer an extremely powerful tool for developing sophisticated structures for example linked lists There are many examples of useful applications for pointers As one simple example suppose you want to sort an array of records TYPE Rec RECORD DUE Name STRING Data AR
117. a type of result function block where the formal parameters are identifiers that describe the variables Cand their data types which will be used within the function These variables do not have to appear in a variabie declaration statement since they are being declared within the function heading DECLARATIONS AND DEFINITIONS Page 6 7 Following the formal parameters is the data type of the result of the function For example FUNCTION SufficientFunds Request REAL BOOLEAN BEGIN SufficientFunds Request lt AmountAvailable END The heading above might identify a function that returns TRUE if a checking account has enough funds to cash a specified check The function block starts with the BEGIN keyword and finishes with the END keyword The statements in between perform the action on the input data when the function is executed The function block takes this form Label declarations Constant declarations Type declarations Variable declarations Procedure function declarations BEGIN END block EI As you can see the block of the function follows much the same form as the program block itself except that a function definition ends with a semicolon rather than a period At some point within the BEGIN END block a value must be assigned to the function name itself This is the way that the result of the function is returned to the program or procedure that invoked it To invoke a function inc
118. able names constants etc are in a combination of upper and lower case and are not underlined Note that reserved words are underlined For clarity s sake therefore this manual deviates from the usual Alpha Micro documentation practice of underlining all output the computer displays on your terminal display We will try to clearly indicate which portions of our examples are entered by you and which portions are printed by the computer CHAPTER 2 GETTING STARTED This chapter is primarily for the benefit of the programmer who is interested in learning Pascal but who has not yet had the chance to become familiar with the language If you are already familiar with Pascal you will probably want to skip to Part I of this book The AlphaPascal System for information on Alpha Micro s specific implementation of Pascal and for operating instructions for the AlphaPascal compiler You may be interested in Section 2 3 of this chapter however which contains a brief demonstration of creating compiling linking and running a small Pascal program The rest of this chapter gives a brief discussion of Pascal and walks you through a quick demonstration of building compiling Linking and running a program under the AlphaPascal system We also show you a small Pascal program and discuss its component parts dal WHAT IS PASCAL The Pascal language is based on the 1970 work of Jensen and Wirth and is related to the amp LGOL family
119. acanssanareaccounesas 10 25 195021 OPENT iol eoque pas ect Xd aga ka 10 25 10 2 14 OPENO Muta auae nu wwe TORES 10 2 15 OPENR senocononsna et omsarssass wrath 10 26 Tie ee PEILE quad uad ke use EE iau eite naaa 10 26 TUE LO RADOU mera das TR ana 10 26 SES RENAME cus emet dubi e aA qu 10 27 ALPHA PASCAL USER S MANUAL CHAPTER 11 CHAPTER 12 10 2 20 SETFILE TOT A se 10 3 SAMPLE PROGRAM TO DEMONSTRATE FILE HANDLING um 10 3 1 Sample Run PD VAGUE 10 5 2 The Program n n e 10 3 5 Program Organization nanooonoaozosos 10 3 3 1 The AMOS file NAMREC INC 10 3 3 2 The AMOS file EMPREC INC 10 3 3 3 The AMOS file FIND PAS MISCELLANEOUS FUNCTIONS AND PROCEDURES 11 1 BASIC FUNCTIONS AND PROCEDURES e n 13 T 1 CHR aa wee OT AA CE 11 1 2 KILCMD we m ae dae Eid le HAS 11 1 3 MARK nannaa M nn aede siu Ra arare E 11 1 4 NEW NAA tai Bag Wah kaya Tho DAG ORD a ala LET mm EA 11 1 6 PRED aa AA AA E plant a 11 1 7 RELEASE wanncnnenaunccenewcennanunene 141 129 SUGE baha Naa ee T 11 2 SPECIAL TERMINAL DISPLAY PROCEDURES 11 2 1 CHARMODE hn WiB R S m o WR WR PUR WA 11 2 2 CRY usw wewskr RU oom m rm m ae SACAR KLAR nU ae 11 2 2 1 Cursor Positioning anes 11 2 2 2 Extended Screen Display Options c anana Rx 1 2 5 INCHARMODE aananananonamaeseszaas 1 2 46 LINEMODE seoconoo aa PON TEL E D in ens MATHEMATICAL FUNCTIONS 12 1 TRIGONOMETRIC
120. age Subroutines Opening closing and specifying files have changed You may now access AMOS files and make full use of the Alpha Micro file system Refer to Chapter 10 Input Output Functions and Procedures for more information on the procedures and functions that allow you to search for open and read and write sequential and random files NOTE Those of you who have done assembly Language programming using monitor calls on the AMOS system will recognize some of the new procedure names such as FSPEC OPEN OPENI OPENO and OPENR AlphaPascal supports an external procedure Library This library contains a series of procedures and functions available to your programs You may write your own external Libraries that make use of the Library provided See Section 16 1 STDLIB for a list of procedures and functions in the library If you wish to access these routines in your programs your programs may not use these names in global identifier definitions since such definitions will override the standard library definitions Tf you wish to access these procedures and functions simply invoke them in your program If they are not defined within that program AlohaPascal assumes that they are in the external Library Changed 30 April 1981 COMPATIBILITY AND CONVERSION Page 3 5 Several procedures and identifiers used by previous versions of AlphaPascal are not supported by the current version BLOCKREAD BLOCKWRITE UNTT
121. ain Counter Counter to produce the value 20 regardless of the value assumed by Counter within the procedure InnerBlock That is exactly what happens 5 6 NOTATION AlphaPascal uses several conventions in handling and representing numbers and strings 5 6 1 NUMBERS Pascal recognizes two types of numbers integer and real The integer numbers are the whole numbers that is they cannot contain a fractional part Real numbers are numbers that contain a decimal point and which therefore contain a fractional part even if that fractional part is zero For example these numbers are integers 231 7 8098 GENERAL INFORMATION Page 5 10 These are real numbers 567 8 725 00 4 318 For information on the REAL and INTEGER data types see Chapter 7 Data Types Pascal has two methods of displaying numbers decimal notation and Scientific notation Decimal notation allows us to represent a number with an optional sign a whole number part a decimal point and an optional fractional part If the fractional part exists there must be at Least one digit on each side of the decimal point For examples 2405 3 Scientific notation is handy for representing very small or very large numbers A number represented in scientific notation is shown as a value multiplied by the appropriate power of 10 To indicate the exponent Pascal uses the symbol E For example 2 4053E 3 represents negative 2 4053 times 10 to the third
122. al Library to use Library code file for VALID PCF Once again you will probably want to answer STDLIB Now PLINK asks for the names of the files you want to Link together Please specify files to be linked into VALID one per iine ending in a blank Line File 1 Enter the specification of the first file then type a RETURN Now PLINK asks for another file File 2 Type a RETURN if you are only Linking one file otherwise supply the file specification of the next module When you have finished entering all module specifications enter a single RETURN See Section 4 4 4 for information on Linking assembly Language subroutines 4 4 5 Updating a PCF File It would be extremely inconvenient to re compile and re link a huge Pascal program every time you wanted to hange a tiny portion of it AlphaPascal allows you to split one program up into a number of files called modules which are Linked together with one main program file You can change a module file re compile just that file and then re Link the changed module into the main PCF file To update a single module make your changes and then re compile that module Now use PLINK to re link the module into the program When PLINK says Do you wish to 1 replace or 2 update VALID PCF enter a 2 followed by a RETURN Now it will tell you what external Library was used to link that PCF file For example The standard library code file for VALID PCF is STDLIB P
123. also note the extensions discussed in Section 3 1 above 7 The program heading file identifiers are scanned but ignored That is if you have any information in the program heading after the program name that information is ignored For example PROGRAM MailBox is equivalent to PROGRAM MailBoxCINPUT OUTPUTD 2 This is because AlphaPascal uses its own form of file handling that is consistent with the AMOS file structure Note however that the remainder of the heading after the program name is scanned and that therefore the program heading must be syntactically correct For example PROGRAM NewAccount will generate an error because of the open parenthesis If you want to use any files other than the predeciared file INPUT and OUTPUT you must use VAR statements to declare them Operator precedence has been changed to make it more compatible with other Language processors on the Alpha Micro system If it is important that your program be able to run under another Pascal that uses Standard Pascal s rules of operator precedence you will have to use parentheses in your expressions to override AlphaPascal s rules of operator precedence This will only become necessary if your expressions use relational Operators to compare Boolean expressions For example if A 8 and D are Boolean variables standard Pascal evaluates IF A B AND C D THEN as IF A B AND C D THEN while AlphaPascal evaluates it in this way
124. am and yyy is the name of its Library If you get this message it either means that you are running with an out of date version of Library vyy or that you are running with a newer version of Library yyy which had to be re created In the latter case you will need to re create your program with PLINK i PART IV APPENDICES APPENDIX A QUICK REFERENCE TO ALPHA PASCAL This appendix gives a quick summary of the Pascal Language as implemented by Alpha Micra For information on a particular Pascal statement or element look in the index to see what pages of this book contain information on that element For a complete description of the standard Pascal language see Jensen and Wirth The Pascal User Manual and Report For a list of all standard identifiers see Section 5 4 2 Standard Identifiers A t PROGRAM STRUCTURE program consists of a heading and a block and it concludes with a period Heading Lock The heading takes this form PROGRAM program name or PROGRAM A block has the form label declaration constant definitions type definitions variable declarations external declarations procedure and function declarations BEGIN statement statement saa statementN END If a file is not a main program file the heading takes the form QUICK REFERENCE TO ALPHA PASCAL Page A 2 MODULE module name MODULE and the block takes the form Label declaration constant definitions
125. am cry cent nim emm cmm D rev came AES NE eere m cm mem nem naga em saga e PRINTING CHARACTERS DECIMAL HEX 32 20 4 33 21 34 22 35 23 36 24 37 p 25 38 26 39 27 40 28 41 29 42 2A d 43 2B 44 2c 45 i 2p 46 2E 47 2F 48 30 49 31 50 32 51 p 33 i 52 34 53 28 od 54 36 55 d 37 56 38 57 39 58 3A 59 38 60 sc 61 I Sh 1 62 36 63 sr 64 40 diem ee ate ttn etm em hm ct ret tte Page B 3 mam aae mae vare mn AE o a AA AA AE ei hE Space Exclamation Mark Quotation Mark Number Sign Dollar Sign Percent Sign Ampersand Apostrophe Opening Parenthesis Closing Parenthesis Asterisk Plus Comma Hyphen or Minus Period Slash Zero One Two Three Four Five Six Seven Eight Nine Colon Semicolon Less Than Sign Than Question Mark Commercial At cutn ies t en nae AOR AR RT SEVA rU OOD AEE AET NOTA EN Gu naeh cari crm AH AG a a en anro ach THE ASCII CHARACTER SET Page Br M RATE LRL A CPI T E re AE ee ee EY ANG gd cL O AA Kcd f CHARACTER OCTAL DECIMAL HEX MEANING AN NERO A eco A e Oe aati dM i A 101 55 41 Upper Case Letter B 102 66 42 Upper Case Letter C 1403 67 43 Upper Case Letter _ i D 104 58 44 Upper Case Letter E 305 69 45 Upper Case Letter
126. apter Basic Functions and Procedures are routines that users of standard Pascal wili probably be familiar with The Last part of the chapter Special Functions and Procedures for File 1 0 contains descriptions of functions and procedures that are particularly for use with the AMOS file structure NOTE You will notice that we use the term file identifier when discussing a file variable rather than the simple term file sometimes used by other Pascal books This is to help avoid confusing the file identifier with the file specification which is the specification of the actual AMOS disk file that is associated with the file variable Using an AMOS file requires that you first declare the file identifier and then associate it with the file specification of an AMOS disk file See Section 10 2 Special Functions and Procedures for File 1 0 for more information on using AMOS disk files especially Section 10 2 12 OPEN O 10 1 BASIC FUNCTIONS AND PROCEDURES These are the Input Output functions and procedures that users of standard Pascal will be most familiar with Later sections in this chapter discuss special input output functions and procedures that allow your programs ta access the AMOS file structure You will often use the procedures GET PUT READ READLN WRITE and WRITELN for transferring data between your program and the users of your program These procedures are also used to transfer data between your program an
127. art Although of course the procedure and function declarations can contain a statement section The file ends with a period even though it cannot end with an END keyword followed by a period Below is a small sample of a module and the main program with which it is Linkeds A MODULE MODULE FUNCTION MAX Arg1 Arg2 REAL REAL BEGIN MAX gt IF Argt gt 4rg2 THEN MAX Argl ELSE MAX Arg2 END End of MAX Y A MAIN PROGRAM PROGRAM Maing VAR Numi Num2 REAL EXTERNAL FUNCTION MAX Arg Arg2 REAL REAL BEGIN Main Program gt WRITE C Enter two numbers READLN Num1 Num2 z WRITELN WRITELNC The Larger number is MAX Num1 Num2 END Main Program 3 5 2 COMPOUND STATEMENTS BEGIN AND END The statement section of the program block starts with a BEGIN keyword and ends with an END keyword The elements within these two keywords may consist of one statement or many and comprise the executable section of the program changed 30 April 1981 GENERAL INFORMATION Page 5 4 Any one statement may be replaced by a combination of statements called a compound statement A compound statement is a series of statements and starts with the BEGIN keyword and finishes with the END keyword By convention the programmer usually indents each compound statement one Level within the program see the example below so that he or she can visually keep track of how compound statements are nested The individual
128. as done and c how many errors occurred If an error occurs you see t reported at the appropriate place in the compilation For example suppose we had left off a statement separator the semicolon at the end of the first line of the program The diagnostic display would look like this AlphaPascal Compiler Version 2 0 0 PROGRAM MYPROG VAR Target REAL Line 1 CINISOP or NG expected inserting 01 NEWCHECK lt 6 PROGRAM lt 10 16 Lines 6 97 seconds 155 02 Lines minutes Total of 1 compilation errors E NOTE If you tell CMPILR to send the diagnostic display to the terminal screen instead of a file CMPILR pauses when an error occurs and gives you a chance either to continue or quit For example Changed 30 April 1981 OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 7 AiphaPascal Compiler Version 2 0 lt 0 PROGRAM MYPROG VAR Target REAL Line 1 CINESOP or O expected inserting Hit RETURN to continue At this point you may continue the compilation by typing a RETURN or you may stop the compilation by typing a Control C in which case you see the message Compilation aborted If an error occurs CMPILR does not generate the PO1 PO2 and PO3 intermediate files this is to prevent you from Linking a program that contains a compile time error 4 3 2 Compiler Options The AlphaPascal compiler has a number of options available to you
129. atement described in Section 10 2 12 to associate the file identifier Datafile with an AMOS disk file NUMBER DAT The RESET procedure closes the file and re opens it for input PROGRAM FileAccess VAR DataFile FILE OF CHAR Entry CHAR Counter INTEGER BEGIN FileAccess 3 OPEN CDataFile NUMBER DAT OUTPUT Open NUMBER DAT for output FOR Counter 1 TO 5 DO BEGIN WRITEC Enter data Get data from terminal READLN Entry DataFile Entry Assign data to buffer var PUT DataFile Write to file END RESET DbataFile Close file and re open for input 7 WHILE NOT EOF DataFile Do Get data till file is empty BEGIN Entry DataFile WRITELN Entry GETibataFile Get data from file END END T FileAccess a NOTE If you use OPEN to open a file for input or if you use RESET the first file component is placed into the buffer variable for you INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 7 10 1 5 READ READLN WRITE and WRITELN The READ and READLN procedures are elaborations of the GET procedure discussed above You should use them only for TEXT files and terminal input WRITE and WRITELN are elaborations of the PUT procedure also discussed above they are for use only with TEXT files and terminal output Although we say that these procedures are for use with TEXT files you will notice throughout this book that we have made wide use of them for transferring da
130. ations and definitions appear at the front of the main program or the procedure or function containing the declared data objects These centralized declarations and definitions greatly enhance the Legibility and organization of your program and aid the compiler in performing error detection You ll remember from Chapter 5 that the declaration and definition part of the program block takes the form Label declarations Constant definitions Type declarations Variable declarations External declarations Procedure and function definitions 6 1 PROGRAM DECLARATIONS The program declaration consists of the PROGRAM keyword It may also contain a program name This program declaration assigns the name of the main program and marks the start of the main program file A program name may be any legal identifier see Section 5 4 Legal Identifiers The program declaration statement takes the form PROGRAM program name DECLARATIONS AND DEFINITIONS Page 6 2 Ors PROGRAM Unlike other versions of Pascal AlphaPascal does not require or recognize any information about external input or output files after the program name in the program declaration Neither does AlphaPascal attach any significance to the program name That is the program name serves only as a type of comment and does not actually identify the file End the program declaration with a semicolon to separate it from the rest of the program statements For example PROG
131. cation takes the form OPENR Cfi tec identifier where file identifier is the file variable associated with the AMOS file you want to open NE NOTE OPENR inputs the first record of the file into the buffer variable 10 2 16 PFILE The PFILE procedure displays on your terminal the AMOS file specification associated with the specified file identifier The invocation takes the form PFILECfile identifier where file identifier is a file variable associated with the AMOS file whose specification you want to see Several of the sample programs in this chapter use PFILE 10 2 17 RADSO The AMOS system stores much of the information used by the file system in a special form called RADSO RADSO compresses three bytes of ASCII data into two bytes of numeric data The RADS procedure converts a String into RADSO form This is necessary if you are going to use the SETFILE procedure since SETFILE expects several of its arguments in RAD50 form For example if you are planning to use SETFILE to change the filename of an AMOS file specification you will do a GETFILE to get that specification GETFILE TheFile Dev Unit Filnaml Filnam2 Ext Proj Prog The elements Dev Fitnam1 Filenam2 and Ext are returned in RADSO form Now vou will do a SETFILE to change the Filename SETFILE TheF ile Dev Unit RADSD NEW O RADSOC NAM Ext Proj Prog leaving the rest of the elements as they were INPUT QUTPUT FUNCTIONS AND PROCED
132. cedures AN AA 6 8 5 6 3 Forward Declarations weacceenucan SES 6 9 ALPHA PASCAL USER S MANUAL Page v O 6 6 4 Formal Parameters saccecunsenavenenneas 0711 6 6 4 1 Value Parameters o oon sea O11 6 6 4 2 Reference Parameters ee 6 12 6 7 EXTERNAL DECLARATIONS anonenacanosanonssrnsn sa 6 12 CHAPTER 7 DATA TYPES Pat pung 5 m DATA TYPES soncosnononsananannos INTEGER aaocoononas uman canosarcaneaosonan REAL anconenasonenam semen ecw seen nnean BOOLEAN mah aa aera ER CHAR usc emm ale mm im Rin nid mid wr RUMOR A RR E User Defined Scalar aronanoononaoanas DE User Defined Subranae oonnnon ooneanasa TURED DATA TYPES nacaononcoonaseas M 1 E s i 5 k3 id i i m ppuan Coo a N YE 8 NI NG FI m3 A d d d 3 BZ PO CO O XA o P7 Poe arene or Packed Data Types eonanocsononao o ARRAY concononanoasas PEE EE E 7 2 2 1 Multi dimensional Arrays STRING ooomaonarnnareran seso da TEXT aa is AA A ale a i s i 5 PFPPP PY H ta 4 gt 2 s a 3 2 Pc ee FILE saca PA ee ee ee MIN M Rime 715 RECORD coo soso er rr ee ee ee sea C 16 7 2 7 1 Variant Parts lt oonaconamnazo aw TETE 7 2 8 Pointer Type n ooooossnasaso AAA 7 19 AL oO o o a 2 PO NG NG PO PO ES X Dan DiN Aa TT pati LI LI H a a E 4 F A E H s E a a i a A a 3 LI 5 a a i a n a d a mg
133. cessary to load the Pascal XLOCK routine into memory However the routine does require one word of data in system memory to Link to the system queue list which contains the locks set by XLOCK This Link is contained in the file DSKO XLOCK SYS 1 4 This file should be Loaded into system memory so that XLOCK may work If XLOCK SYS is not loaded into system memory then the AlphaBASIC subroutine XLOCK SBR must be This is because the AlphaBasic XLOCK will contain within itself a link to the system queue blocks which contain the Locks set by both XLOCK routines For more information see the XLOCK documentation There is no problem if both XLOCK SBR and XLOCK SYS are in system memory at the same time The Pascal XLOCK will use XLOCK SBR so that BASIC and Pascal are using the same list of locks The lock values defined below LOCK1 and LOCK2 are required for each lock LOCKT is called the MAJOR LOCK and LOCK2 is called the MINOR LOCK If a value of O is set in either Lock then that lock becomes a wildcard and matches all values in that position For instance a LOCK1 of and a LOCK2 of 0 Locks out all locks with a LOCK of 3 Any other user that tries to use a LOCK of 3 will be locked out If LOCK1 is set to 0 then all locks will be set For more information see a description of the BASIC XLOCK subroutine 14 6 1 The XLOCK Subroutine XLOCK is an external function Therefore it must be specified as such in the Pascal program that u
134. changes when you allocate the dynamic variable By doing a MARK followed by a NEW you have a value that tells you where on the heap the variable allocated by NEW is Located The way to free up heap space used by the dynamic variables allocated via NEW is to use RELEASE see Section 11 1 7 below NOTE Be very careful when using MARK and RELEASE unwise use of these procedures can leave you pointing to areas of memory that are not bart of the heap thus causing unpleasant and unpredictable results 11 1 4 NEW The NEW procedure allocates a dynamic variable The invocation takes the form NEWCvariable identifierd where variable identifier is the pointer to the variable allocated by NEW To access the variable allocated via NEW use the pointer variable variable identifier For more information on NEW and dynamic variables see Section 7 2 8 Pointer Type The sections on MARK and RELEASE in this chapter give information on using MARK NEW and RELEASE to allocate and de allocate dynamic variables on the heap 11 1 5 ORD The ORDOO function returns the ordinal number of the argument in the scalar data type of which X is a member Accepts arguments of type CHAR or user defined scalar types Returns am INTEGER result The function invocation takes this form ORD variable identifier or constants For example each character displayed by the computer has a numeric value associated with it called the ASCII value which spec
135. character press the RUB key sometimes Labeled DELETE or DEL ARROW KEY To move the cursor around on the screen use the keys marked with arrows labeled with a left arrow right arrow upcarrow and downarrow For example to move up on the screen press the up arrow key If your terminal does not have arrow keys you will use these control characters instead Control H To move left Control J To move down Control K To move up Control L To move right If VUE 1s new to you you may want to ask the System Operator to place into your account a copy of the VUE initialization file in which the menurdisplay option has been enabled VUE will then display a summary of its commands when you enter command mode You may also want to ask the System operator to modify the VUE initialization file so that the default extension is set to PAS which means that VUE will expect you to edit PAS files and thus will not require you to enter a file s extension unless you want to edit a non PAS file Changed 30 April 1981 GETTING STARTED Page 2 7 2 5 2 Compiling and Linking a Pascal Program The first step after creatina your program is to compile it using CMPILR After you have compiled it the program is still not ready to run until you use the Linker PLINK Both PLINK and CMPILR are themselves programs written in Pascal Chapter 4 Operating Instructions and Characteristics discusses the operation of PLINK and CMPILR in detail For no
136. cification consists of Device Unit Filename Extension Project number Programmer number For example DSK CUSTID DATUT100 3J where DSK is the Device 0 is the Unit CUSTID is the Filename DAT is the Extension 100 is the Project number and 3 is the Programmer number You can use several procedures to associate the file specification with the file identifier e g FSPEC SETFILE EXTENSION You can then use OPENI OPENO OPENR RESET or REWRITE to open the file Or you can combine these two steps by using OPEN which takes the form OPEN file identifier filespec mode where file identifier is a file variable filespec is the file specification in string literal or variable form and mode INPUT OUTPUT or RANDOM tells AlphaPascal whether the file is going to be used for input output or in the case of random files random INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 17 update With INPUT and RANDOM modes besides associating the file identifier with a file specification OPEN also inputs the first record of the file for you 3 Once you have set a file up to start doing 1 0 you can use GETS and PUTs or READS and WRITES to transfer data between your program and the file 4 The final stage in using an AMOS file is to close it using the CLOSE procedure Closing the file makes sure that the last record updated in the file gets written out to the file and makes the file available for being opened again You
137. ck1 appears before the END keyword of Blocke The BEGIN END label may take the form of any legal identifier and must be separated from the keyword by a colon Changed 30 April 1981 DECLARATIONS AND DEFINITIONS Page 6 74 6 5 CONSTANT DEFINITIONS Defining constants will be helpful whenever you have a string or numeric Literal that is used frequently within a orogram a Literal is important to understanding the logic of the program or a literal may possibly be changed in future versions of the programa For information on constants see Section 8 2 Constants The constant definition takes the form CONST identifier number or string identifier number or strings gt a identifierN number or string i For example instead of repeating the expression Radius 3 1415927 throughout a program you might want to define the constant Pi CONST Pi 3 1415927 Then wherever your program used to say Radius 3 1415927 you can now say Radius Pi This keeps your program easy to read Also if at a future date you have to change a literal in your program it is now a simple matter since you have only to change one constant definition statement instead of every occurrence of that literal 3n the program As an example of a strina literal consider the statement WRITELN You have entered an invalid number try again tf you use this string more than once you might want to replace it with a con
138. compiles MODULI PLINK then Links it into TRSRCH PCF peu assumes that you want to use the external library TRSRCH was originally Linked under ALPHA PASCAL USER S MANUAL PART II SUMMARY OF ALPHA PASCAL The next nine chapters discuss the elements of the Pascal language as it has been implemented by Alpha Micro If you are interested in a quick summary refer to Appendix A A Quick Reference to AlphaPascal CHAPTER 5 GENERAL INFORMATION This chapter contains very general information about AiphaPascal program concepts such as basic program structure statement separation and spacing legal identifiers compound statements scope of identifiers etc Far detailed information on specific elements of a Pascal program see the Index and Appendix A Quick Reference to AlphaPascal 3 1 BASIC STRUCTURE OF A PROGRAM This section Lists the major elements of a Pascal program We ll talk more about each element in the following paragraphs but this will give you a general idea of what goes where Every Pascal program follows the general form Heading block The heading follows this form PROGRAM program name ori PROGRAM NOTE Standard Pascal requires that you follow the program name with a set Of names that are concerned with program input and output for example PROGRAM Schedule INPUT OUTPUT AlphaPascal however ignores these names and you may omit them altogether However make sure that the pr
139. contains the characters 123 but does not represent the number 123 The fourth example contains the characters END but does not represent the keyword END If you wish a string to contain a quotation mark place two quotation marks where you want the single quotation mark to appear For example You don t say A string may be defined in a constant definition For example CONST Message Error Type CR to recover We then say that Message is a string constant Or a string may be used as a string literal For example WRITELN Do not forget to write enable the disk NOTE AlphaPascal includes the data type STRING as a standard data type Pata of type STRING consists of a group of characters data of type CHAR rather than a single character For information on CHAR and STRING see Chapter 7 Data Types CHAPTER 6 DECLARATIONS AND DEFINITIONS One of the important features of Pascal is that it requires that you define and name the data objects you are going to use in a program before you reference those objects For example if you are going to be using a variable named Cost you must declare that variable at the start of the program or procedure in which that variable appears Besides declaring variables you must also declare the program name Labels functions and procedures and modules In addition you must define any numeric or string constants you are going to use as well as any data types All declar
140. d special storage areas called files The other procedures discussed in this section PAGE RESET and REWRITE are used only with files Remember that when we talk about files we are referring to the special data type FILE that in AlphaPascal can be associated with AMOS disk files INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 2 Three special pre declared file identifiers exist that you should be aware of INPUT Specifying INPUT tells AlphaPascal that you want to use the terminal as an input file For example when you use READLN to get data from the terminal keyboard READLN EmployeeNumber Dept you have implicitly said READLN CINPUT EmployeeNumber Dept In other words if you omit a file identifier from the arguments given to the READLN procedure READLN assumes you want to use INPUT INPUT is a TEXT file QUT PUT Specifying OUTPUT tells AlphaPascal to use the terminal as an output file For example when you write data to the terminal display via the WRITELN procedure WRITELN Enter your Employee Number you have implicitly said WRITELN OUTPUT Enter your Employee Number OUTPUT is a TEXT file KEYBOARD The KEYBOARD file identifier acts much the same as INPUT except that if the terminal is in Charmode the characters typed by the user of your program will not echo on the terminal display For example CHARMODE WRITELN Enter password READ KEYBOARD Password Asks the user of your p
141. d by R5 and so will also be referred to as the R5 stack ALL other registers RO R4 are available for any purpose to your assembly routine Arguments are placed on the R5 stack in reverse order That is the Last argument appears on the top of the R5 stack For example if we have the following program in AiphaPascal File TEST1 PAS PROGRAM EXTERNAL PROCEDURE demol x y INTEGER BEGIN demo1 10 200 END then upon entry to our assembly Language subroutine 20 will be on the top of the R5 stack referenced as AR5 and 10 will be under it on the R5 stack referenced as 2 R5 procedure to print its two INTEGER arguments in order might then be DEMOT MAC File DEMOT MAC COPY SYS START MOV 2 R52 R1 Get first argument DCVT 0 2 Print it in decimal CRLF MOV aR5 R1 Get second argument DCVT 0 2 Print it in decimal CRLF ADDI A R5 Remove arguments from R5 stack RTN Return to pascal DEMOT would then be assembled with MACRO and the resulting program file DEMOT PRG would be renamed to DEMO1 PSB in order to allow it to be Linked into a code file by PLINK ASSEMBLY LANGUAGE SUBROUTINES Page 15 3 When called as a function rather than as a procedure your routine wilt receive an additional three words containing zeros on the top of the R5 Stack These words serve no purpose when writing assembly routines and may be immediately removed by executing an ADDI 6 R5 Their presence is required for inte
142. de and that VUE is ready for you to type your program in Start typing the sample program in Section 2 2 just as you would if you were using a typewriter Type in the example exactly as shown including all semicolons quote marks and parentheses If you make a mistake you may erase single characters by using the RUB key sometimes labeled DEL or DELETE To erase the characters on an entire Line type a Control RUB That is hold down the CONTROL key while you press the RUB key The cursor which may appear as a small white rectangle triangle Line or other symbol marks your place on the screen the next character you type appears at the cursor position If more extensive corrections are needed you may back up in the display by using the arrow keys to move the cursor back and forth in the text on the screen 1f your terminal does not have these arrow keys you must move the cursor by typing Control J Control H Control K and Control L For example to move the cursor to the left hold down the CONTROL key and type an Ha When the cursor is positioned just to the left of the error you can overwrite the error by typing your new characters over the oroblem spot Or if you do not want to overwrite the error type a Control From this point on the new characters you type will be inserted into the current Line rather than overwriting it To resume overwriting characters type another Control Changed 30 April 1981 GETTING
143. dures that read and write disk files since the new AlphaPascal is fully integrated into the AMOS file structure Pai l i lf your programs were written under previous versions of UCSD AlphaPascal you will need to transfer your programs to AMOS files before you begin to perform any necessary conversions To do so use the UCSD AlphaPascal programming system which was provided only in earlier releases of AiphaPascal 1 At AMOS command level enter the UCSD AlphaPascal programming system by typing PASCAL followed by a RETURN PASCAL When you see the initial prompt Command ECdit RCun FCile CCompile X ecute dCebug nit Hialt Type an F 2 You are now communicating with the Filer You see this prompt Filer GCet SCave WChat NCew L dir RCem CChng TCrans D ate QCuit To see what is in your Library type L Now you see the question What volume Enter a colon followed by a RETURN Now you see a list that might Look something Like this SCR ROMAN TEXT 4 28 Jun 80 POSTFIX TEXT 4 28 Jun 80 2 files 8 blocks used 26 unused This is a list of the files in your Library 5 You see the Filer prompt again To write one of the programs out to an AMOS file enter T a The Transfer function asks you Transfer what file enter one of the files listed in the directory For example COMPATIBILITY AND CONVERSION Page 3 3 Transfer what file ROMAN TEXT b Now Transfer asks To what file Enter REMOTE and type a
144. e Delete Inquire List Quit L ED ALLEN EDNA N 35 years old sex female ARROWSMITH JACK C 51 years old sex male ZUCKER SUE ELLEN R 23 years old sex female Enter option A dd Change Delete I nquire List Quit q GET lt The screen clears gt Leaving AlphaPascal Random File Demonstration INPUT OUTPUT FUNCTIONS AND PROCEDURES 10 5 2 The Program PROGRAM EmployeeMaintenance TYPE NameRecord RECORD First STRINGD113 Middle CHAR Last STRING 151 END NameRecord EmpRecType Control Data Unused EmpRecord RECORD CASE EmpRecType OF Data Name NameRecord Age INTEGER Sex Male Female NextDataRecord INTEGER Control Page 10 31 FirstDataRecord ARRAY L A 2 OF INTEGER FirstUnusedRecord INTEGER Unused NextUnusedRecord INTEGER END CEmpRecord EmpFileType FILE OF EmpRecord Global Variables VAR EmpFile EmpFileType RecNum PreviousRecNum INTEGER CantrolRecord EmpRecord FUNCTION SameNames Namet Named NameRecord BOOLEAN Returns TRUE if Namel Namee BEGIN SameNames 13 Namel First Name2 First AND Name1 Middle Name2 Middie AND Namel Last Name2 Last END SameNames Changed 30 April 1981 INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 32 FUNCTION Find Name NameRecord BOOLEAN Searches for specified record in EmpFile Maigi true if found leaving file positioned at desired record RecNum z Cont
145. e PAS extension This source file may be in any account but the P01 PO2 and PO3 files for the program will be generated in the device and account you are logged into Changed 30 April 1981 OPERATING INSTRUCTIONS AND CHARACTERISTICS 2 Page 4 6 4 3 1 The Diagnostic Display After you have given CMPILR the name of the source file you want to compile it asks Diagnostic file name lt return gt for terminal The diagnostic file contains information about the program compilation You will usually want to see this information on the screen as the compilation proceeds and therefore will enter a RETURN If you want this information sent to a file so that you can have a permanent record of the compilation enter a valid AMOS file specification For example Diagnostic file name return for terminal D TAG RET The default extension is LST The diagnostic display might look something Like this depending on the program you are compiling AlphaPascal Compiler Version 2 0 yes NEWCHECK lt 4 PROGRAM lt 10 16 Lines 7 07 seconds 152 83 Lines minute No compilation errors The diagnostic display above shows the Line numbers at which the procedures within the program begin Line 6 for the procedure NEWCHECK Line 10 for the main program Each dash indicates the compilation of one program Line The last three lines tell you a how many lines were in the program b how quickly the compilation w
146. e Violet Blue and Green You could define a subrange scalar type TYPE ColdColors Violet Green You may define a subrange of any user defined or standard scalar type except type REAL Use the type declaration statement in this format TYPE Type name lowerlimit upperlimit The symbols tell Pascal that you are establishing a subrange UpperLimit and Lowerlimit are the beginning and ending elements of the subranges For example TYPE Decimal O aa 9 tells Pascal that we want to define a type named Decimal that can assume values in the range of 0 through 9 of the standard data type CHAR We can then declare a variable of that type VAR Number 3 Decimal NOTE You may also directly declare a variable to of a subrange without using a type declaration statement For example VAR Number Of as 9 7 2 STRUCTURED DATA TYPES Structured data types are built up of simple scalar data types Several keywords can be used to define structured data types ARRAY RECORD SET and FILE DATA TYPES Page 7 7 You may define your own structured data types in much the same way that you were able to define simple scalar types See Section 7 1 5 User defined Scalar Two structured types have been pre declared for you STRING and TEXT 7 2 1 Packed Data Types Before we discuss the various structured data types available to you we d Like to digress for a moment and talk about how the computer repres
147. e enable alternate character set 24 End Line drawing mode disable alternate character set 25 Set horizontal position 26 Set vertical position 27 Set terminal attributes NOTE You should be aware that these options can be selected only if your particular terminal and terminal driver program are capable of carrying them out For example not all terminals can perform an erase to end of screen function Note that most terminals do not support all of the options listed above unsupported options will be ianored by your terminal driver 11 2 3 INCHARMODE The INCHARMODE function returns a Boolean result If it returns a TRUE then you are in charmode a FALSE indicates that you are in linemode See the paragraph below MISCELLANEOUS FUNCTIONS AND PROCEDURES i Page 11 9 11 2 4 LINEMODE The LINEMODE procedure returns a terminal to the normal input mode after it has been set into character mode via the CHARMODE procedure discussed in Section 11 2 1 above The invocation takes this form LINEMODE While in Line mode all input is ended by a carriage return and character editing is enabled Character echoing occurs as you type the characters not when they are read CHAPTER 12 MATHEMATICAL FUNCTIONS The following functions accept one or more numeric arguments For information on invoking functions and on writing your own functions see Section 6 6 Function and Procedure Declarations 12 1 TRIGO
148. e 9 7 BEGIN MainMenu WRITEC Enter your choice from the menu above 2 READLN MenuChoice CASE MenuChoice OF TTR ComputeTax tg UpdateAccount c PrintReport tpt poBilling END End of CASE J3 END D MainMenu 7 The program block above performs the proper procedure based on the user selection from the main menu NOTE What happens if none of the case labels match the selector Standard Pascal says that such an event is undefined AlphaPascal simply says that if none of the case labels are matched then control passes to the next program statementa See the next paragraph for information on using an ELSE clause to catch a situation where no match occurs 9 1 2 1 CASE UF ELSE AlphaPascal allows a unique variant to the CASE statement the CASE OF ELSE statement This statement takes the form CASE expression OF Case Label Case label statement Case label Case label statement2 Case label Case label statementN ELSE statement For example BEGIN 1 MainMenu 3 CUWRITEC Enter your choice READLN MenuGhoice 7 CASE MenuChoice OF TA ComputeTax g o UpdateAccount ct PrintReport tpi DoBilling ELSE WRITELN No valid choice Didn t enter A B C or D ho END D MainMenu Y Notice that the ELSE clause takes the place of the final CASE statement END keyword NOTE See Section 8 5 CASE Expressions for information on using the CASE construct to cond
149. e END keyword followed by a period The period indicates that the end of the program has been reached rather than just the end of a group of statements within the program As a final word on program structure we would like to mention that your program can consist of more than one file The advantage of splitting your program up into multiple files is that when a change needs to be made to one of the files you only have to re compile the one file and then re link the files rather than re compile all of the files lf your program does consist of multiple files only one of those files will follow the main program format we discussed above the rest will follow a slightly different format This is because only one main program file may be Linked together with other files These non program files follow this format MODULE module name block MODULE block This heading tells the Pascal compiler that the file is not a main program file and that it is part of a multiple file program The module name identifies this non program file and does not necessarily have to be the GENERAL INFORMATION Page 5 3 same name as that assigned to the actual file or to the main program The block takes this form Label declaration part Constant definition part Type declaration part Variable declaration part External declaration part Procedure and function declaration part As you can see the file does not contain a statement p
150. e a linked list as follows TYPE Node RECORD Data INTEGER Next Node ENDE Notice that we said that the data portion of the List element will hold integer data you can use whatever data type you want Let s build a simple Linked List and then display it in reverse Changed 30 April 1981 DATA TYPES PROGRAM LinkedList TYPE Pointer Element END VAR 1 X INTEGER P List BEGIN LinkedList WRITEC Enter integer READLN OO List s NIL WHILE X lt gt O DO End BEGIN m NEWCPO P Data X P Next L List x st E WRITEC Enter integer READLN OO END P lt List WHILE P lt gt NIL DO BEGIN MOE WRITELN P Data P 35 PO Next END END T LinkedList If you enter the numbers Other useful examples would RECORD Data Next 1 28 involve Page 7 22 Element INTEGER Pointer Pointer gt Get first number of List gt Initialize list gt List when X 0 gt Allocate dynamic variable Put number into list gt Set List pointer to next element gt 1 Ta and 4 5 6 7 you see displayed 65 4 3 2 inserting elements into a list deleting elements from a List by updating the List pointers NOTE AlphaPascal contains the procedures MARK and RELEASE which you use in combination with NEW to make use of a stack like structure called the heap See Chapter 11 for information on MARK and RELEASE
151. e above the ELSE applies to the last IF THEN statement if 850 is FALSE Flag is set to 1 As another example STATEMENTS Page 9 6 PROGRAM DoubleElse VAR AQB C D gt REAL BEGIN DoubleElse WRITEC Enter A B C Di 5 READLN A B C D Enter values for A B C D 9 IFA B THEN IF C D THEN WRITELNC No Else ELSE WRITELNC ELse1 ELSE WRITELNC Else2 END DoubleElse 7 As we said ELSEs are nested That means that the second ELSE is applied if the first IF clause A B is false the first ELSE is applied if the second IF clause CD is false So the output from the program above is as foliows A B c p Output True True No Else False True Else2 True False Etsel False False Else 9 7 2 CASE OF The CASE statement allows you to select one out of a group of statements for execution The CASE statement takes this form CASE expression OF Case label Case label statement1 Case label Case label statement2 a a Case iabel Case label statementN END The expression called the selector is evaluated and its value must be the same as one of the case labels A selector must not be of type REAL and it must be of the same type as the case labels You may have as many case labels as you like but each case label may appear oniy once in any one CASE statement When a matching case label is found the statement following that case label is executed For example STATEMENTS Pag
152. e pointer enables Pascal to permit dynamic data structures by giving you a way to point to an element of such a structure It takes the form obiect type Pascal provides a standard constant NIL which points to nothing A d EXPRESSIONS Expressions use operators to combine variables constants and function calls into larger units This section gives information about each of these components of an expression A 4 1 Operators Operators have precedence which you can override by incuding parentheses in the expression The unary operators are performed before ali other operators next the multiplying operators are performed follawed by the adding operators Then the relational operators are performed Lastly the Boolean operators are applied If several operators in an expression have the same precedence execution is performed from left to right A 6 1 1 Assignment iw QUICK REFERENCE TO ALPHA PASCAL Page A A 4 1 1 1 The Modifying Assignment Operators The modifying assignment operators are ts Addition ma Subtraction Multiplication z Division A 4 1 2 Arithmetic Operators unary operator Identity unary operator Sign inversion Addition Subtraction Multiplication DIV Integer number division Real number division MOD Modulus A 4 1 5 Relational Operators Equality lt gt Inequality lt Less than gt Greater than Ex Less than or equal or set
153. e right of itself This means that AlphaPascal evaluates the expression above as Result 5 10 Score Cards 32 Pairs Singles That is Cards is set to 32 Pairs minus the value of Singles Then the value of Cards is subtracted from 10 Score That value is assigned to the variable Result As another example of the use of the assignment operator in an expression consider a situation where you want to initialize a group of variables by setting their values to zero Pascal does not have a multiple assignment statement However the expression Averages Total Sum Median 0 causes Pascal to perform a multiple assignment as a side effect of evaluating the expression 8 1 2 1 Modifying Assignment Operators AlphaPascal contains a set of special operators called modifying assignment operators These operators allow you to assign Values to variables by modifying the value of the variable instead of replacing that value For example the assignment expression RecordCount 120 telis Pascal to replace the value of RecordCount with the number 120 A modifying assignment expression of the form RecordCount 120 tells Pascal to take the value of RecordCount and modify it by adding 120 to it Pascal then assigns this new value to RecordCount We thus modify rather than replace the value of RecordCount In effect the expression above is equivalent to RecordCount RecordCount 120
154. e the name of each locally declared procedure as CMPILR comes to it C or D Pascal tells you if data D or code C is being generated for the program line lv and dsp R Internal information used by the compiler abo Indentation level Tells you what nesting level the current program Line is at ic ilc Internal code location counter This number tells you how many total bytes have been allocated at this point in the program compilation for the object code of the current procedure or function The ic lc number can come in handy Later when you debug programs Tf you interrupt program execution and backtrace that program the backtrace gives you the IPC number the Interpreter Program Counter The IPC is the number designated by ic lc in the program Listing You can thus compare your backtrace with your program Listing and see exactly where the problem occurs Also if a run time error occurs the error message gives the IPC in the procedure at which the error occurred e g Value range error in PROGRAM at IPC 64 within FILL PAS For information on backtracing see Section bra Interrupting a Programa 4 3 2 4 The Page Option SP The P option allows you to start a new page in the Listing by telling the compiler to insert a form feed at that point in the program Listing SP is ignored if the SL option is not in effect 4 3 2 5 The Quiet Options SA and a Q designates the quiet compile option T
155. e2 field name field nameN field typeN END For example a record to represent a date could be defined as TYPE Dates CT RECORD Month Jan Feb Mar Apr May Jun Jul Aug Sept Qct Nov Dec Day CN es Year INTEGER END You may then declare a variable of type Date VAR Deadline Date such a variable would contain three pieces of information the month the day and the year However all the information may be treated as a unit if you want to do so f If several fields share the same type you may list them on one Line separated by commas You may also nest record definitions For example TYPE Credit x ao eis RECORD Finances RECORD Checking Savings Loans INTEGER END Name 2 STRINGISOJ Birth Date END After defining a record you may then declare a variable of that type For example VAR Customer Credit To select a field of a record use both the name of the record variable and the name of the field separated by a period For examples IF Customer Name Smith John C THEN CheckCredit You may assign the value of record to another For example given VAR Customer Employee Credit you may assign the contents of record Customer to record Employee DATA TYPES Page 7 18 Employee Customer which is equivalent to Employee Finances Customer Finances Employee Name 3 Customer Name Employee Birth Customer Birth 7 2 7 1 Variant Parts Records of the sa
156. each variable before that variable is used See Section 6 5 Variable Declarations and Chapter 7 Data Types for information on data types and declaring variables For information on choosing a valid name for a variable see Section 3 4 Legal Identifiers A variable identifer may be in the form of an expression For example consider the case where we want to refer to an element in an array NewArrayl2 4 3 99 8 4 IF THEN ELSE EXPRESSIONS Wherever an expression is legal AlphaPascal allows you to include an IF THEN ELSE expression This allows you to conditionally evaluate one of two alternative expressions The construct takes the form IF condition THEN expression ELSE expression Note that you must include the ELSE clause if you use the IF THEN construct in this way For example IF Credit gt IF BillAmt gt 1000 THEN 2000 ELSE 0 THEN WRITELNC OK charge it ELSE WRITELN Sorry send it C 0 D 2 The statement above contains this expression IF BillAmt gt 1000 THEN 2000 ELSE 0 This evaluates either to 2000 or to 0 depending on whether or not the variable BillAmt has a value greater than 1000 Therefore the statement above either evaluates to IF Credit 2000 THEN WRITELNC OK charge it ELSE WRITELN Sorry send it 0 D0 25 OPS IF Credit gt O THEN WRITELNC OK charge Es ELSE WRITELN Sorry send it COD EXPRESSIONS Page 8 9 Remember that expressions can also conta
157. eceding argument has wrong type The preceding argument must be a variable expression The preceding must be of type CHAR 30 April 1981 ALPHA PASCAL COMPILER ERROR MESSAGES Page C 4 CCALEXT EXITOO where x is a standard func or proc is illegal You may only supply EXIT with the PROGRAM keyword or the name of your own procedure or function that you want to exit you may not supply the name of a function or procedure in the Library TCALFILJ Preceding argument must be of FILE type CCALFRMI Formal procedures and functions not implemented CCALINTA The preceding argument must be of type INTEGER CCALIOR Preceding argument must be of type INTEGER or REAL CALLERI C expected assumed missing CCALNRSI Preceding argument must be a pointer or non REAL scalar C CALOPMI INPUT OUTPUT or RANDOM expected INPUT assumed See Chapter 10 for information on file identifiers LCALPAC Must be a packed array of char or a char element CCALPTYI The preceding must be a pointer variable CCALRDP It is illegal to read into a packed cher field CCALRDT Arguments to read must be INTEGER REAL CHAR or String LCALSCNI Only and lt gt are permitted here CCALSEX The preceding must be a string expression CCALSVR The preceding must be a string variable CALTFA Too few arguments supplied CCALTGS The preceding must not be a string or a real CCALTGT The preceding constant is of incorrect type for variant See Chapter 7 for information on R
158. ed its next few questions and knows what files to Link together and what external Library to use You see Loading program and Library dictionaries OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 12 This teils you that PLINK js getting ready to process your file For each file that you are Linking PLINK tells you when it begins working on that file For example Processing NEWMOD Next PLINK tells you what globally declared functions and procedures are being linked into your PCF file These routines are in your program and the external Library For example Linking in global func proc ERRCHECK Linking in global func proc PROGRAM At Last PLINK is finished and begins to copy the resolved code into the PCF file Transferring temporary file to new code file PLINK s final message tells you that it is finished VALID completed Now let s get back to the questions PLINK asks when it is determining which files to Link together NOTE Keep in mind when answering PLINK s questions that PLINK converts all of your input to upper case 4 4 1 Linking a New PCF File If you use PLINK to create a PCF file and that file does not already exist PLINK knows that you are Linking a new program and not trying to replace or update an existing program For example Suppose you have told it that you want to create VALID PCF It tells you Creating new code file VALID PCF Now it asks which external Library you want to use for the new p
159. eletes the specified file if it already exists Default extension is DAT For example OPEN INP TEST RANDOM associates the AMOS file TEST DAT with the file identifier INP and opens the random file for input and output Most of the sample programs in this chapter use the OPEN procedure NOTE OPEN in INPUT or RANDOM mode inputs the first record into the buffer variable 10 2 13 OPENI OPENI is a variation of the OPEN procedure it opens a sequential file for input The invocation takes the form OPENI Cfile identifier2 where fileridentifier is a file variable associated with the AMOS file you want to open If the file does not exist or if the file identifier has not been associated with an AMOS file via an FSPEC or SETFILE OPEN generates an error OPENI inputs the first record of the file into the buffer variable 10 2 14 OPENO OPENO is a variation of the OPEN procedure it opens a sequential file for output The invocation takes the form OPENO CFile identifier2 where file identifier is the file variabie associated with the AMOS file you want to open If the file already exists or if the file identifier has not been associated with an AMOS file via FSPEC or SETFILE OPENO generates an error INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 26 10 2 15 OPENR OPENR is a variation of the OPEN procedure it opens a random file for input and output The file must exist and may not already be open The invo
160. ement Y im EX X 5 X471 It assigns the element X and the elements X45 through X 7 to the set Y Yau may mix sets of the same base type For example DATA TYPES Page 7 13 VAR 3x 4 E SET OF SAP Ks AE A BEGIN Y im Y X END You may use modifying assignment operators on sets So for example you could rewrite the statement above to Y Xi The operations that you can perform on a set are those defined by set theory set union set difference set intersection set equality set inequality lt gt set inclusion lt and gt and set membership IN The empty set CJ is a valid set If we define a type Newset that is a set of integers TYPE NewSet SET OF 1 10 VAR Seti NewSet Set Newset Result Newset and then assign values to the sets Set and Set2 Set Tasa Set2 5 6 7 8 93 We can use the sets Seti Set2 and Result to talk about the operations you can perform on sets Set Union An element is contained in the union of SET1 and SET2 if and only if it is an element of SET1 or SET2 or both For example Result Set Set2 Result is the set 1 9 gt Set Difference An element is contained in the difference of two sets if and only if it is an element of SETI but not an element of SET2 For example Result z Seti Set2 Result is the set 1 43 gt Set Intersection An element is contained in the intersection of two sets
161. en rene cte mm uem onim cm enne seme nen nece cue cn m cum curo nen een om CHARACTER OCTAL DECIMAL HEX MEANING NULL 000 0 06 Null fill character SOH 001 1 o Start of Heading STX 902 2 02 Start of Text ETX 003 3 f 83 End of Text ECT 004 4 04 End of Transmission ENQ 005 5 05 Enquiry ACK 006 6 06 Acknowledge BEL 007 7 Xe Bell code BS 010 8 08 Back Space HT 011 9 09 Horizontal Tab LF 012 10 oa Line Feed VT 013 11 08 Vertical Tab FE 014 42 d oc Form Feed CR 015 13 OD Carriage Return so 016 14 06 Shift Out SI 017 TS OF Shift In DLE 020 166 Y 10 Data Link Escape poi 021 17 11 Device Control 1 DEZ i 022 18 12 Device Control 2 bc3 023 19 E 1 4 Device Control 3 DES 024 20 14 Device Contral 4 NAK 025 21 45 d Negative Acknowledge SYN 026 22 16 Synchronous Idle ETB 027 23 End of Transmission Blocks CAN 030 24 18 Cancel EM 031 25 19 End of Medium SS 032 26 14 Special Sequence ESC 033 27 18 Escape FS 034 28 PAG d File Separator 6S 035 29 10 Group Separator RS 036 30 dE Record Separator US 037 31 IF Unit Separator THE ASCII CHARACTER SET CHARACTER LESER ome esee cavi cano ctm n mio cm ees qu
162. ents data types in memory Structured data types sometimes require quite a bit of room in memory For example consider how many memory locations must be allocated for a structure such as ARRAY 0 10 0 10 0 10 0 10 OF CHAR where more than 10 000 elements must be handled NOTE We discuss the ARRAY data type in Section 7 2 2 ARRAY O It is often the case that only one element of such a structure is stored in one memory Location even though there physically may be room for more To help minimize memory use Pascal allows you to create packed data structures in which the data in the structure are packed together in a minimum amount of space To create a packed data type include the keyword PACKED in your type declaration tatement TYPE Type name PACKED data type For example TYPE CustomerID PACKED ARRAY 1 503 OF CHAR You may also pack records by preceding the keyword RECORD with the word PACKED Only the array or record immediately following the PACKED keyword is affected and any nested arrays or records must be explicitly packed As one example of the efficiency you can sometimes gain in packing data consider the following data structure of type RECORD TYPE Date RECORD Month Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Day Taw Sk Year O 99 END Unpacked the data above takes up three words of memory packed it takes up only one word NOTE Some types of data cannot be packed e g real
163. erN type QUICK REFERENCE TO ALPHA PASCAL Page A 4 A 3 BATA TYPES The data type telis Pascal what range of values the declared variable may assume and what operations may be carried out on those variables bata types are simple data types or structured data types A 5 1 Simple Data Types A simple data type is the basic data type of which structured data types are built The simple data type is called a scalar type Such a type contains a set of elements and those elements are ordered A 5 1 1 Standard Data Types The standard data types are INTEGER A non fractional number in the range 32767 through 32767 REAL A floating point number significant to 11 digits 12 for integer values with an exponent range of roughly 1E 37 to 1E37 BOOLEAN The standard scalar type FALSE TRUE CHAR 7 A single ASCII character A 3 1 2 User defined Scalar Types A scalar data type takes the form Cidentifier element1 identifier element2 identifier elementN or a subrange type of another already defined scalar type of the form first element Last element A 5 2 Structured Data Types Simple data types can be organized into larger units called structured types A type definition or variable declaration of a structured data type that includes the keyword PACKED tells the compiler to minimize internal storage for that data type at the possible expense of execution time Far example instead of l VAR LongLine A
164. ery sixtieth of a second on most systems and every fiftieth of a second on other systems the actual amount is specified by CLKFRQ in SYSTEM INI Word contains the most significant part of the returned value Word and Word2 must be declared INTEGER variables The procedure invocation takes this form TIME Wordi Word2 For examples PROGRAM TestTime VAR First Second INTEGER BEGIN TestTime TIMECFirst Second WRITELNC The time is First Second END TestTime 3 When the program above was run at 5 40 02 PM it printed The time is 56 2086 NOTE Because the clock contents are stored as a 32 bit unsigned value Word2 may sometimes be interpreted and displayed by the computer as a negative number 14 9 TOD TOD takes no arguments and returns a real number corresponding to the number of seconds since midnight according to the time of day Internally the time of day is converted from a two word integer to a real number and then divided by the clock frequency defined in SYSTEM INI Therefore the resolution on 60 cycle systems is to within 01666 seconds and on 50 cycle systems is to within 02 seconds You will probably find TOD to be of most use for timing purposes or for calculating the time of day SYSTEMS FUNCTIONS AND PROCEDURES Page 14 12 14 10 ERROR HANDLING PROCEDURES AND VARIABLES Whenever an error occurs the AlphaPascal system prints an appropriate message including the location
165. ever see this error message Please report it and the circumstances under which you saw it to Alpha Micro In x x must be of pointer or FILE type In xy y must be compatible with index type of x Only enclosing func identifiers may be used as variables In x y y must be a field of the RECORD x In x y x must be of RECORD type Standard function identifiers may not be used as variables For a list of the standard identifiers see Chapter 5 In xEyJ y must be of non REAL scalar type XXX 1s undefined XXX is not a TYPE CONST VAR FTELD PROCEDURE FUNCTION identifier In x x must be numeric Wrong BEGIN END identifier XXX expected For information on BEGIN END Labels see Section 6 2 Label Declarations The oreceding case label appears more than once The preceding case label has wrong type DO without WHILE FOR or WITH ELSE without IF or CASE Final FOR value must be of scalar type FOR variable and final value have incompatible types 30 April 1981 ALPHA PASCAL COMPILER ERROR MESSAGES Page C 6 STMF IK STMFIT 5TMFYF CSTMFVK CSTMGTOI CSTMMOLI ESTMPEXO CSTMPEXJ CSTMRTLI CSTMTWIJ CSTMULBI LSTMUWRJ ESTMWRTI ESTMWTSI CSTRERRI CTOKEDG CTOKEOF CTOKFDGJ CTOKILCI CTOKINFJ TOKIRG CTOKLTL3 CTOKNINJ ETOKSLSI CTRMNBNI CTRYINSI CTRYINSI CTRYINSJ UTRYINS CTRYMIS CTRYSCN CTRYSCNJ UTRYSCNI TYDFWPJ CTYDJNKJ CTYPRTFI CTYPCTKI CTYPCTRI CTYPIXB Changed In
166. ew program you might Link it with the NEWLIB Library Your new program would thus be Linked with NEWLIB which in turn has its own Library STDLIB There is no limit to Library nesting WRITING AND MODIFYING AN EXTERNAL LIBRARY Page 16 4 There are several things you should keep in mind when writing an external Library 1 If an external procedure or function is declared both in a program and in a Library which it uses then the definition within the program is in effect while execution resides in the program and the definitions within its Libraries are in effect while in its Libraries 2 If you change a procedure from pascal to assembly language or from assembly Language to pascal it is wise to re create re link that program and all the programs which use it as a library Any references to the procedure which are not re linked will treat it as the wrong kind of code 3 Similarly if while updating a program you overide a definition in a Library which was formerly accessible there is no garauntee that all references to the definition will be updated unless you re link the program and ali the programs which use it as a librarv 4 Ilf a library is updated with PLINK it is not necessary to update the programs which use that library However if the library must be completely re created all programs which use that Library will need to be re created Thus it is desirable to avoid the need to re create a Library PLINK does not allow
167. f no extension is supplied For examples PROGRAM TestFspec VAR DataFile FILE OF CHAR UserFile STRING Counter INTEGER BEGIN TestFspec gt WRITEC Please enter file specificaton READLN UserFile Counter FSPEC DataFile UserFile DAT 2 WRITELN C Number of characters Counter WRITEC File spec is PFILE DataFile END TestFspec 3 You can use FSPEC to input an entire command Line not just a file specification If the user of the program enters NEW OLD the program prints Number of characters 3 File spec is NEW DAT Then we can use the DELETE procedure DELETE UserFite 1 Counter to leave the remainder of the user input OLD 2 in UserFile Note that we used PFILE to print the name of the file associated with the file variable DataFile and that the FSPEC function added the default extension of DAT INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 22 10 2 8 GETFILE The GETFILE procedure allows you to find out exactly what file specification is associated with a specific file identifier The invocation takes the form GETFILECfile identifier Dev Unit Filel File2 Ext Proj Prog The arguments are declared INTEGER variables The data is returned as integers because file specifications are stored internally by AMOS in a special numeric form called RAD50 RADSO format compresses three bytes of ASCII data into two bytes of numeric data In other words GETFILE returns the f
168. f the file doesn t exist ERASE can t erase it but no error is generated and no harm is done If the file does exist ERASE erases it and leaves the way clear for OPENO and CREATE We ve rewritten the small program in Section 10 2 3 CREATE to include the ERASE procedure PROGRAM TestErase VAR RanFile FILE OF CHAR Counter INTEGER BEGIN TestErase Counter 13 FSPEC RanFile NEWFIL DAT ERASE RanFile Make sure file doesn t already exist CREATE CRanFile 20 END TestErase 3 10 2 5 EXTENSION The EXTENSION procedure forces the specified extension in the specification of the AMOS file associated with the specified file variabte The invocation takes the form EXTENSION Cfile identifier ext INPUT OUPPUT FUNCTIONS AND PROCEDURES Page 10 20 where file identifier is the file variable associated with the AMOS file Li and ext is a string literal or variable that designates the extension you want to force to the file specification For example PROGRAM TestExtension VAR TheFile FILE OF CHAR Counter INTEGER BEGIN TestExtension gt Counter FSPEC TheFile NEWFIL DAT EXTENSION TheFile LST PEILE TheFile END TestExtenstion 7 The program above associates the AMOS file NEWFIL DAT with the file identifier TheFile Then it uses the EXTENSION procedure to change the extension from DAT to LST Notice the use of the PFILE procedure to print the AMOS file specification NOT
169. f you are going to link a number of files together into one program each file must contain an DECLARATIONS AND DEFINITIONS Page 6 13 external declaration for every element it needs to reference if that element was declared and defined in another file For example if the variable CustomeriD was declared in file File and you need to reference that variable in File2 File2 contains the external declaration EXTERNAL VAR CustomerID STRING There are some things you should keep in mind when making external declarations 1 You may not externally declare Labels constants or types If you need to have common definitions of these items use include files For information on include files see Section 4 3 2 2 The Include Option 12 If you are going to use data files in your program the declarations for those data files must be in the main program file That is data files may not be externally declared in your main program file 5 You must be very sure that the types given in your external declarations exactly match the types given in the original main declarations For example if one file has the declaration VAR NetWork CHAR the external declaration in another file for that variable must specify type CHAR EXTERNAL VAR NetWork CHAR CHAPTER 7 DATA TYPES We ve already mentioned that a variable is a symbol that can represent more than one data value We ve also said that you must dec
170. f you are interested in Learning to program in Pascal you might want to take a Look at one or more of the following textbooks Conway Ra Gries D and Zimmerman E C A Primer on Pascal Winthrop 1976 Grogono P Programming in Pascal Addison Wesley 1978 Kieburtz R 8 Structured Programming and Problem Solving with Pascal Prentice Hall Inc 1978 Schneider G M Weingart S W and Perlman D M An Introduction to Programming and Problem Solving with Pascal John Wiley amp Sons 1978 Wilson I R and Addyman A M A Practical Approach to Pascal Springer Verlag 1978 1 3 GRAPHICS CONVENTIONS USED IN THIS BOOK The symbol BET indicates the place in an example where you would press the terminal carriage return key if you were entering the example into the computer The carriage return key on the terminal keyboard is usually labeled RET or RETURN and telis the computer to accept and process the current line INTRODUCTION Page 1 4 It is often confusing when looking at a program in a new computer Language to determine which elements are an inherent part of the Language for example program statements and which elements are to be supplied by the programmer To help eliminate some of this confusion our sample programs follow these conventions Reserved words are all upper case and underlined Standard identifiers are all upper case but not underlined All user identifiers for example vari
171. field for example it is 311 digits AlphaPascal will not truncate the number but will use the necessary number of spaces If the number is a REAL number you may also specify Y the number of digits to be printed to the right of the decimal point for example for dollar values you would probably want to specify 2 AlphaPascal rounds the REAL number to the specified number of places it does not truncate it INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 11 Although you will probabiy find the optional formatting arguments to be of most use in printing numbers you may also print data of type CHAR or STRING specifying a minimum field width By combining formatting of numbers and strings you can construct tables and charts in which titles and numbers are neatly lined up See the output of the sample program below for a simple example Here are some sample outputs the E symbol indicates a blank WRITECT 1 1 0 1 0 1 161 1 WRITECO O 1 0 100 010 0 0012 1612 1 1612 1 23E 12 0616100 01b6 001261E1261 1812 1 23E 12 WRITECO 0 6 2 1 0 6 2 100 010 6 2 0 0012 6 2 1 23E 12 6 2 6160 0016151 0055100 01565666 008 0 00 Below we give a sample program that demonstrates both formatted output and the use of files INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 12 PROGRAM FormatOutput VAR Report FILE OF REAL Year Profit REAL I INTEGER BEGIN FormatOutput OPEN Report YTD DAT OUTPUT P
172. file identifier as specifying the Pascal data structure with which the actual file will be associated Several of the functions you can use to handle files accept a file identifier and a file specification For example the FSPEC procedure accepts three arguments the file identifier an AMOS filespec and a default extension For instance FSPECCFTLe1 ACCNTS DAT 2 where Filet is the file identifier and ACCNTS DAT is the AMOS file we want to associated with that file variable The standard identifier TEXT has been pre declared for you this identifier is equivalent to FILE OF CHAR See Section 7 2 4 above for information on TEXT Tala RECORD A record is a data structure that consists of a number of components called fields Unlike arrays the record elements do not have to be of the same type and you access the elements by name not by subscript You can use records to develop very sophisticated data structures e g array of records file of records pointers to records When you declare a record type you are defining a template for a group of variables that contain related information but which do not have to be of the same type To define a record use the type declaration You will provide the name of the record and names and types of the fields within that record DATA TYPES Page 7 17 TYPE Identifier RECORD field name field nameN field typel field name field nameN field typ
173. for later on in the program GENERAL INFORMATION 5 4 1 Reserved Words Below is list of the Pascal reserved words as identifiers AND DIV EXTERNAL IF NIL PROCEDURE THEN WHILE ARRAY DO FILE IN NOT PROGRAM TO WITH 5 4 2 Standard Identifiers Below is these identifiers them Constants FALSE Tvpes INTEGER TEXT Predeclared files INPUT Procedures Library refer to Contents a list of all AlphaPascal However be TRUE BOOLEAN OUTPUT reserved words BEGIN DOWNTO FOR LABEL RECORD TYPE standard identifiers careful not to MAXINT REAL KEYBOARD variables and functions NOTE variables and functions are for internal use of the compiler You may not CASE ELSE FUNCTION MOD OR REPEAT UNTIL CHAR and For a list of all functions and procedures available for your use A Quick Reference to AlphaPascal or to the Table of Page 5 6 use these CONST END GOTO MODULE PACKED SET You may redefine unintentionally redefine STRING Several of these procedures standard GENERAL INFORMATION ABS ARCSINH CHR COS DELETE ERROR EXP FILLCHAR GETFILE INSERT LCS LOCATION MARK NEW OPENO PFILE PUT RADSO R DR RELEASE RLN SEEK S INH SAR SARIP TIME ucs WRC WRR XMNT 5 5 SCOPE OF IDENTIFIERS Because Pascal is a a nested structure naturally into ARCCOS ARCCOSH ARCTAN ARCTANH CLOSE C
174. formation concerning input or output files from your program heading 4 The INTERACTIVE file type is no Longer supported Change any occurrences of the INTERACTIVE file type in your programs to TEXT It might be easiest to just redefine INTERACTIVE at the front of your programs via a type statement TYPE INTERACTIVE TEXT 5 Previous versions of AlphaPascal expected a UCSD file specification for the argument of the compiler include option SI Now the SI option request accepts an AMOS file specification The default extension is INC If you have used the I compiler option you will have to change your file specifications to valid AMOS file specifications and make sure that those files exist For more information on include files see Section 4 3 2 2 The Include Option 125 6 If it occurs in your programs remove the SEGMENT keyword mg Note that the operator precedence used by AlphaPascal is different from that of standard Pascal and previous versions of AlphaPascal You may need to check expressions in which Boolean expressions are compared with relational operators to make sure that the expressions will be evaluated correctly See Section 8 1 1 Operator Precedence for more information Besides changing your programs so that they will run under AlphaPascal you might also want to add some of the new AlphaPascal features listed in Section 3 1 above As an example instead of the statement TOTAL TOTAL SUM
175. g The function invocation takes this form characters in the specified LENGTH Source string For example PROGRAM TestLength VAR State STRING BEGIN TestLength State California WRITELNC Number of characters in state LENGTH State 7 WRITELN C Number of characters in ae LENGTH 90247 END TestLength 3 The program above prints Number of characters in state 10 and Number of characters in zipcode 5 13 1 7 POS The POS function returns the position of the first occurrence of the specified characters in the specified source string If POS can t find the specified characters it returns a zero The invocation of this function takes the form POSCPattern Source string For example PROGRAM TestPos VAR Source STRING BEGIN TestPos 3 Source The requested account number is HAA234 567 23228 WRITELNC The account number begins at character position POS C HAA Source END TestPos e The program above prints the message The account number begins at character position 33 STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 6 13 1 8 STRIP The STRIP procedure strips trailing blanks from the specified string That is STRIP removes any blanks that are at the end of the string The invocation takes the form STRIP SourceString where SourceString must be a string variable For example PROGRAM TestStrip VAR Source STRING BEGIN Test
176. g yyy XXX yyy Or zzz expected inserting xxx XXX vyy Or zzz expected inserting yyy xxx expected yyy assumed missing xxx expected scanning XXX or yyy expected scanning XXX yyy OF zzz expected scanning x present and x never declared for some x Junk after type definition scanning In ARRAY Ex OF y y must not be a FILE type in CASE x OF x must be a scalar type identifier in CASE x OF x must not be of type REAL Array is too large 30 April 1981 ALPHA PASCAL COMPILER ERROR MESSAGES TYPIXR CTYPIXTJ TYPLGHJ CTYPNST CTYPRFFJ TYPRGEJ CTYPSCIJ TTYPSRRI CTYPSTAI CTYPSTBI CTYPSTKI CTYPSTR C TYPSXR TYPSXT CTYPTTEJ CVRDFWPJ CVRDJNKI CXPRAFLI CXPRLPXI CXPRSSPI In ARRAY Cx OF v x must not be of type REAL In ARRAY x OF y x must be a scalar type X y where x gt y is illegal beclarations too deeply nested Record fields must not be of FILE type Haay where x and y are incompatible A string constant identifier must not appear here Subranges of type real are illegal Set is too Set is too In SET oF In SET OF must have 1 lt x lt 255 STRING xJ STRING xJ In CASE x x present Junk after large targe must be lt SET OF 0 4095 x x must be a scalar type x x must not be of type REAL where x is not an integer OF tag type is incompatible with x and x never declared for some x lt variable definition
177. generated for a library this number is called the version number Whenever you link a program AlphaPascal writes the version stamp and version number of the external library you are using to the PCF file being Linked Whenever you execute a program PRUN checks to make sure that the version stamp for that program matches one of the program stamps in the current external Library This makes sure that the current Library is not a completely different Library than the one the program was Linked with If the Library is a modified version of the Library the program was linked with checking to see that the version stamp in the program exists in the List of version stamps in the Library makes sure that the Library is not an earlier version than the library with which the program was linked If the Library and program are not compatible you cannot run the program with that version of the library instead you must re link your program with the current Library PRUN displays the following message if the program version stamp and number of the library are older than those of the program Wrong version of xxxx for use with yyyy where xxxx is the external library and yyyy is your PCF file If you update an external library check to see if your old PAS files have to change because of the revisions For example if a hypothetical procedure REVERSE now expects three arguments while a previous version expected two your programs will have
178. ger k bad TAN argument 20 ARCCOSHOD where x lt 1 21 FACTORIAL x where x is a negative integer 22 ARCTANHOO where abs x gt 1 23 POWER x y where x lt 0 and y is a fraction In the case of 1 0 errors there is some additional information namely the type of error and the file involved which is available SYSTEMS FUNCTIONS AND PROCEDURES Page 14 14 PROCEDURE ERRORTRAP VAR INFOP INFOREC BADFILEP TEXT BEGIN INFOP ERRORINFO IF INFOP XEQERR 10 1 0 Error THEN BEGIN BADFILEP INFOP ERRFIB MRITEC I 0 error INFOP FILERC has occurred in PFILE BADFILEP WRITELN END STDERRORTRAP END In the above example if an 1 0 error has occurred we display the file error code CINFOP FILEROO and the name of the file involved INFOP ERRFIB ERRFIB is a pointer to the most recently processed file which is why we first save it in BADFILEP before writing to the terminal otherwise our message would read 21 0 error xxx has occurred in TTY regardiess of the actual file in which the error occurred Here is a list of the I O error codes They are the standard codes used by AMOS I 0 Error Code Meaning 1 File specification error e Insufficient free memory for INIT 3 File not found amp File already exists 5 Device not ready 6 Device full 7 Device error amp Device in use 9 Illegal user code 10 Protection violation 11 Write protected 12 File type mismatch 13 Dev
179. ges at the places in the program where the errors occurred The Listing takes a form that looks something Like this depending on the program you are compiling Line proc iv il dsp ic le 1 561 0 1 1 SL DIAG 2 7 DA 9 1 1 PROGRAM Validate Validate numeric entry make R 01 9 1 1 sure that it is between 1 and 100 7 4 P1 O 1 4 So mm p1 O 1 1 VAR Target REAL 6 Dh 03 1 Po 02 0 2 4 FUNCTION ErrCheck Local REAL BOOLEAN a De 0 2 7 Function checks entry If 100 lt number lt 1 goce Dae 0 7 ErrCheck reports error by returning a TRUE gt Mee e T eg 0 BEGIN Begin function ErrCheck Vee Qo et dg 0 ErrCheck Local lt 1 OR Local gt 100 12 C2 0 2 12 END End function ErrCheck 7 13 CZ 0 2 40 14 C1 1 1 0 BEGIN Main Program 15 ee x 1 2 WRITEC Enter a number between 1 and 100 2 16 C1 1 1 45 READLN Target 17 C1 1 1 65 TF ERRCHECK Target 18 C1 2 1 69 THEN WRITELN Invalid entry try again 19 85 To 8 112 ELSE WRITELN Very good Correct entry 20 gt Ot N1 157 END Main Program r compilation errors On the right you see a listing of the program The left contains additional information about the program Linef This is the number of the program line on the right hand side of the display The rest of the information on this Line refers to this program Line Changed 30 April 1981 OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 10 Proc You se
180. global or local in scope depending on where they are declared k Most implementations of Pascal while they may include extensions to the Language also contain a subset of Pascal which adheres firmly to the standards for the Language as set forth by Jensen and Wirth This means that programs written in standard Pascal are transportable between computer systems on which Pascal ie implemented GETTING STARTED Page 2 3 2 2 SAMPLE PROGRAM If you have never before seen a Pascal program you may be interested in taking a look at the small simple program below Determine what X is deducted from your gross salary PROGRAM Salary VAR Gross Takehome Deductions Percentage REAL BEGIN Begin Program Salary Print questions and read answers from terminal WRITE What is your gross salary READLN Gross WRITE What is your takehome salary READLN Takehome Deductions Gross Takehome Percentage i 100x Deductions Gross WRITELN They keep Percentage percent of your salary END End Program Salary NOTE To help you keep track of which words in the program are lements of the Pascal language and which are variable names and data supplied by you we have written in upper case and underlined those words called keywords that are actually part of the Pascal language 0f course you do not underline such keywords when you write your own Pascal programs Those words that are in upper case but
181. gnores Line feed characters Za Character Data 3 GET Data The procedure invocation takes the form READ Cfile identifier list of variables If you omit the file identifier READCList of variables INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 8 READ assumes that you want to use the file INPUT that is that you want to input from the terminal keyboard The READ arguments must be separated by commas For example READ DataFile CustomerID CustomerName where DataFile is a file variable and CustomerID and CustomerName are variable identifiers Or i READ Linesize Pagesize PageNumber where Linesize Pagesize and PageNumber are variables to be input from the terminal NOTE If you input more than one variable via the READ or READLN procedure those values should not be input separated by commas For example given READCA B CO The response 12 3 is legal but the response 15 225 is not valid If you respond with an illegal number for example you input an A for a variable of type INTEGER AlphaPascal assigns a zero to that variable instead of generating an error It is the responsibility of your program to check the validity of data input by the READ procedure 10 1 5 2 READLN READLN inputs a list of variables from a file or the terminal keyboard You should only use READLN on TEXT files It differs from READ in that it reads an entire line of data up to a carriage return Line
182. h codes into the SWITCHES variable SYSTEMS FUNCTIONS AND PROCEDURES Page 14 35 For example if you want to use the BANNER and DELETE switches to tell the Line printer spooler program to print a banner page and delete the file after printing it load SWITCHES with 5 BANNER code DELETE code If you set SWITCHES to 0 or do not specify one value of a switch pair SPOOL uses the default switches for the selected printer Switch codes BANNER 4 NOBANNER 2 DELETE 4 NODELETE 8 HEADER 16 NOHEADER 32 FF 6 NOFF 128 WAIT 256 COPIES An integer variable or expression that specifies the number of copies to be printed If COPIES is O the Line printer spooler program prints one copy FORMS A string variable or expression that specifies the form on which the file is to be printed If FORMS is a nulli string the Line printer spooler uses the NORMAL form LPP An integer variable or expression that specifies the number of Lines per page SPOOL only uses this value if you have specified the HEADER switch in the SWITCHES variable If you omit LPP the spooler program uses the default value for the specified printer WIDTH An integer variable or expression that specifies the width Cin characters of the print line for header printing If WIDTH is 0 the spooler program uses the default value for the specified printer 14 6 XLOCK AND GETLOCKS XLOCK and GETLOCKS are two assembly language subroutines that allow setting clea
183. hange List or display employee records 10 3 1 Sample Run A sample run looks Like this We will underline the information that the user of the program types in PRUN DEMO lt The screen clears gt AlphaPascal Random File Demonstration Do you wish to re create employee file Y RET How many records to you wish to use 20 RET RET lt The screen clears gt Enter option Ajdd Change Delete Inquire Ldist Auiti A GED Last Name ZUCKER First Name SUE ELLEN Middle Initial R RET How old is SUE ELLEN 23 GED Is SUE ELLEN male Y SET Enter option A dd Change Delete Idnquire L ist Qluitl A GED Last Name ARROWSMITH BET First Name JACK Middle Initial C En How old is JACK 51 RED Is JACK male Y RET Enter option A dd C hange D elete Dnquire LO ist Quit A GED Last Name ALLEN RET First Name EDNA RET Middle Initial N GED How old is EDNA 35 RET Is EDNA male N BEN INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 30 Enter option A dd Ohange Delete Dnquire List uiti LEN a ALLEN EDNA N 35 years old sex female ARROWSMITH JACK Cz 51 years old sex male ZUCKER SUE ELLEN R 23 years old sex male Total of 3 employee s Enter option CA dd Change Delete Dnquire List Quit GED Last Name ZUCKER BET First Name SUE ELLEN Middle Initial R How old is SUE ELLEN 23 GED Is SUE ELLEN male N RET Enter option A dd C hang
184. hanged 50 April 1981 OPERATING INSTRUCTIONS AND CHARACTERISTICS 5 Page 4 8 purpose of the I option is to save you from having to duplicate frequent ly used declarations or lines of code The include file can contain any valid program elements as Long as those elements can legally be inserted at the place in the program where the include file option occurs for example you will not use the 1 option request in a program s variable declaration section to include a file that contains a program header NOTE You cannot nest include file requests That is the include file may not itself contain an include file request E 4 5 2 5 The List Options L L and L The L option request tells the compiler to send a listing to an AMOS file You do not see a program Listing if you do not use the SL option Supply a valid AMOS file specification For example SL DSK1 DIAG 23 27 The Listing will now be written to the specified file The default file extension is LST If you do not give a file specification when you use the SL request CMPILR creates a listing file bearing the name of your source file and a LST extension in the account vou are logged into Of course you may not create a listing file outside of the project of the account you are logged into For example if you are logged into DSK0 0100 23 and try to create the listing file DSKO LIST LSTE200 2 the AMOS system will respond with a protection violation error
185. hat you wilt use the Alpha Micro screen oriented text editor VUE to create your programs You must also use the Linker COMPATIBILITY AND CONVERSION Page 3 2 PLINK to Link any compiled program whether or not it consists of more than one file See Chapter 4 Operating Instructions and Characteristics for complete instructions Expression handling has been considerably enhanced 1 You may now include the assignment operator in an expression For example 5 X t 7 The expression above is equivalent to 5 X 7 and means Let X assume the value of 7 and then be added to 5 Wherever an expression is legal you may include an IF THEN expression of the form lF condition THEN expression ELSE expression For example Year i IF Feb Leap THEN 29 ELSE 28 337 If Feb equals the value Leap then Year assumes the value 294337 otherwise it assumes the value 284337 3 Wherever an expression is legal you may include a CASE expression of the form CASE value OF valuel expression vaiue2 expression ELSE expression Far example WRITECCASE Errorcode OF 2 Illegal input Number too large Number too smalt undefined error VM Ni ma ELSE 7 AlphaPascal now recognizes modifying assignment operators These operators are tz Adding assignment operator Um Subtracting assignment operator Multiplying assignment operator pm Dividing assignment operator COMPA
186. he COPY function creates a new string of the specified number of characters whose contents are taken from the specified source string starting at the specified index The function invocation takes this form COPY Source strina Tndex Size of returned string For example Changed 30 April 1981 STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 3 PROGRAM TestCopy VAR Source Target Position STRING INTEGER 20 aR BEGIN TestCopy Source 5 Jonathan R Smith Position POS S Source Find position of Last name Target COPY Source Position 5 WRITELNC The customer Last name is Target WRITELN Last name position in source string is Position END End TestCopy The program above prints The customer last name is Smith and Last name position in source string is 13 Notice that we used the POS function discussed below in Section 13 1 7 to determine the position in the source string of the character S 13 1 5 DELETE The DELETE procedure removes the specified number of characters from the source string starting at the specified position The procedure invocation takes this form DELETE Source string Index Number of characters where Source string must be a string variable For example PROGRAM TestDelete VAR Source STRING Position Size INTEGER BEGIN TestDelete gt Source Now is the time for all good men Position POS all Source
187. he bits are ordered from low order to higher order in each word and from first word to Last word For example SET OF 34 19 requires two words of memory The first three bits corresponding to 0 thru 2 are unused To test for the presence of the element 18 one would perform a bit test an the second word of the set with a mask of 4 ASSEMBLY LANGUAGE SUBROUTINES Page 15 5 15 2 2 9 Arrays Arrays require one or more words The elements of an array appear im order in memory In packed arrays the elements of an array may each occupy on a few bits otherwise each element will appear on a word boundary Fields appear from Low order to high order in a word and may not cross word boundaries 15 2 2 10 Records Records require one or more words The elements of record appear in order in memory in a fashion similar to arrays 15 2 2 11 Files Files are actually an internal kind of record format The details of this format are not being made available as they will change as versions of AlphaPascal change 15 2 5 Error Exit Should you wish to generate an error from your assembly Language subroutine it is preferable that you call the Pascal system s ERRORTRAP procedure rather than display an error and exit to AMOS directly Otherwise there is no guarantee that open files will be closed correctly To signal an error you must perform a proper return from your routine but in addition advance your return address by executing IW2
188. he queue for its turn to be printed SPOOL allows you to specify on which printer the file is to be printed the number of copies to be printed the form on which it is to be printed whether the file is to be deleted after it is printed etc The current version of SPOOL AMOS version 4 4 AlphaPascal version 2 0 and Later is fully compatible with the current BASIC SPOOL subroutine In other wards the only information you must supply to SPOOL is the specification of the fiie you want to print all other parameters are optional However any unspecified arguments must be replaced by a null value STRING null or INTEGER 0 based on the type of the argument This is because Pascal functions and procedures require a fixed number of arguments The following definitions of switches and error codes are provided in the include file SPOOL INC To use insert SI SPOOL into the appropriate place in your program 14 5 1 Switches To make life easier switch values are available as constants For a description of SWITCHES see below The constants would be BANNER 1 NOBANNER 2 DELETE 4 NODELETE 8 HEADER 16 NOHEADER 32 FF 64 NOFF 128 WAIT 256 SYSTEMS FUNCTIONS AND PROCEDURES Page 14 4 14 5 2 Error Codes The error codes returned by SPOOL are provided in a TYPE declaration at the beginning of a program The TYPE command has the form TYPE SPOOLERROR SPOOLED NOSPOOLERALLOCATED BADPRINTERNAME OUTOFQUEUE
189. his option request tells the compiler to give you a brief diagnostic display leaving off procedure names and line numbers To turn fuli display mode back on the default condition use the Q option code 4 3 2 6 The Range Check Options SR and R The R option tells the compiler to turn off range checking that is the compiler does not output additional code to perform checking on array subscripts and assignments to subrange type variables Programs compiled with range checking off run slightly faster however since the compiler is not checking for range errors if an invalid index or assignment is made by your program the run time package will not stop the program when that error occurs You Changed 30 April 1981 OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 11 should not turn off range checking until your program has been tested and you are absolutely sure that your program runs without error To turn range checking back on the default condition use the R option 4 4 THE ALPHA PASCAL LINKER The Linker PLINK reads the POT P02 and PO3 files created by the compiler and resolves the files into a single executable program You may use PLINK to Link multiple files together into one program However even if your complete program consists of only one file you must use PLINK on that file to generate an executable program file The final file created by PLINK has the PCF Pascal Code File extension Al
190. ice does not exist 14 Illegal block number 15 Buffer not INITed 16 File not open 1 File already open 18 Bitmap kaput 19 Device not mounted 20 invalid filename in the examples so far we have always been calling STDERRORTRAP to handle our errors STDERRORTRAP always aborts to AMOS without returning with the SYSTEMS FUNCTIONS AND PROCEDURES Page 14 15 exception of a Control C followed by a command to resume Thus the ERRORTRAP procedures themselves have aborted to AMOS in most circumstances in addition STDERRORTRAP resets INFOP XEQERR to zero before returning if execution is to be resumed This is because errors MUST NOT occur in the error handler itself for obvious reasons ALphaPascal assumes it is executing an error handler whenever XEQERR is nonzero If an error does occur within an error handler the message TAttempt to call ERRORTRAP while in ERRORTRAP is displayed a direct abort to AMOS is made without closing any open files Thus by reseting XEQERR to zero STDERRORTRAP signals to AlphaPascal that error handling is finished and further errors are again acceptable Should vou decide not to cali STDERRORTRAP at all please keep in mind the following points 1 The only errors from which vou may safely resume execution are 8 a Control C and 10 1 0 error An attempt to resume execution by returning from ERRORTRAP with any other errors will probably crash the system 2 It is acceptable to use EXIT to abor
191. if and only if it is an element of both SET1 and SET2 For example Result Set x Set Result is the set 51 gt Set Equality Seti Set2 is TRUE if and only if every member of Set is also a member of Set2 and every member of Set2 is also a member of Sett DATA TYPES Page 7 14 lt gt IN Result Seti Set2 Result is FALSE gt Set Inequality Set1 lt gt Set2 is TRUE if and only if Seti Set2 is FALSE Result Set lt gt Set2 Result is TRUE Set Inclusion The relation Seti lt Set2 is TRUE if and only if every member of Sett is also a member of Set2 In other words Set lt Set2 is TRUE 1f Set is included in Set2 Result Seti lt Set2 Result is FALSE 6 9 lt Set2 is TRUE Set Inclusion The relation Set 1 gt Set2 is TRUE if and only if every member of Set2 is also a member of Set1 In other words Seti gt Set is TRUE if Set2 is included in Seti If X lt Y is TRUE then Y X is TRUE Set Membership 1f X is of the type declared as the base type of Set il then X IN Set is TRUE if and only if X is contained in Seti For example Result 5 IN Set1 Result is TRUE Result 26 IN Set Result is FALSE gt The IN operator takes as a left argument a simple data type variable or constant e g CHAR or INTEGER the right argument must be a set of that data type e g set of CHAR or set of INTEGER Below is a small sample program that uses sets
192. ifiers a a a e a o 2 2 577 SEEK ma vow wow a aa a ve s we r SEMICOLON wow oo a bla an BG Sequential Files a s a 10 15 SET e a uw cc o 21244574 Set operators 713 8 7 SETFILE vox op cow a vao ce PORES Setting file Locks fue x c cedes P45 SHAFT 2 5 CA AA ero Simple data tynd UU o Her i cae der din GS SEN a wow cee uem wy taal SINH ex sr tad NE SIZEOF 2 4 oe x 9 ow we a NG Changed 30 April 1981 ALPHA PASCAL USER S MANUAL Page Index 9 Spacing conventions s e s e 5 2 SPOOL Qo deer hes et E owes Row ee 1453 Spool switches a s anu SPOOL INC uu a wo SOR Aa PP 1226 SORT e ees a Is Stack a daan O A lt 2 Standard constants s s e a s BeF Standard data type a a a a a 771 Standard identifiers a a 1 4 295 5 5 to 576 Standard Pascal e s ane Statement label s s a 672 Statement separator a e e 5 2 Bk Static variables s s a a a 7 19 STDERRORTRAP a no a a a n a o 14 13 STIDLIE Ka nian a See OFA STR a a 4 Eo Wan wouw uc mo 2G STRING aa o do a a BO PED Pri 15 4 String constant s s s a 5 11 String constants s a a a 671 8 7 STRING data type aa e s s a a 5 11 String functions and procedures CONCAT ln a a 13 COPY ai as 13 DELETE ou cae ee Se a 137 INSERT tae e xo aa OES LOS e a a dw e a ay ES LENGTH Aca 9 ai Gan a 13 du oM AO STRIBC Say lg a Ve wo a a
193. ifies its position in the set of ASCII characters Tf you use the ORD function on an ASCIT character ORD will return to you the ASCII value of that character that is its ordinal number in the ASCII character set For example WRITELNCORD C A 225 Changed 30 April 1981 MISCELLANEOUS FUNCTIONS AND PROCEDURES Page 11 4 returns the decimal number 65 the ASCII value of the character A You may also include an identifier for a user defined scalar type For example PROGRAM TestOrd TYPE DAYSOFTHEWEEK MON TUE WED THUR FRI BEGIN TestOrd WRITELNC Ordinal number of THUR is ORD THUR O WRITELN Ordinal number of D is ORD D D END TestOrd gt The program above prints the ordinal number of the character D in the ASCII character set and the ordinal number of THUR in the user defined scalar type DAYSOFTHEWEEK NOTE The ordinal numbers for the elements of DAYSOFTHEWEEK are MON O TUE 1 WED 2 THUR 3 FRI 4 11 1 6 PRED The PRED function returns the predecessor of the specified scalar argument The invocation of the PRED function takes this form PRED CeLement For example let s say that we defined the scalar type Cardinal to contain the elements First Second and Third TYPE Cardinal First Second Third Since the elements of a scalar data type are ordered we can find out what element is previous ta the specified item by using the PRED function For example IF PRED Second
194. ile specification in RADSO form Filel and File2 are the first three and second three RADSO characters of the filename Although GETFILE may not sound too useful by itself by doing GETFILEs on more than one file you can compare elements of the specifications for those files and by using SETFILE described in Section 10 2 20 below you can actually change those elements For example consider the program below It asks for the specifications of two data files needed for input if those two files do not exist on the same device and unit the program moves the files to the System Device DSK0 so that they are on the same disk device and unit INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 23 PROGRAM TYPE DataFile FILE OF CHAR VAR Dev Unit Filed FileB Ext Proj Prog INTEGER Devi Uniti FileA1 FileB1 Ext1 Proj1 Progl INTEGER MailLabel Addresses DataFile BEGIN Main Program WRITELNC Enter the specifications of your two data files WRITELN WRITEC File 1 O READLN UserSpec WRITEC File 2 READLN UserSpect OPEN Maillabel UserSpec OUTPUT Open the user specified files OPEN Addresses UserSpeci OUTPUT GETFILE MailLabel Dev Unit FileA FileB Ext Proj Prog GETFILE CAddresses Dev1 Unit1 FileAl FileB1 Ext1 Proj1 Progt See if files are on the same disk gt IF Dev lt gt Devt OR Unit lt gt Uniti THEN BEGIN WRITE You have asked for files PFILE USerSpec W
195. in string constants or variables Consider the following small program that conditionally assigns a value to ErrorReport PROGRAM Recovery VAR ErrorFlag BOOLEAN ErrorReport STRING BEGIN Recovery C Frorfiag FALSE ErrorReport IF ErrorFlag THEN An error occurred ELSE No error WRITELN ErrorReport END Recovery ES NOTE including an IF THEN ELSE construct in an expression is not a feature of standard Pascal Note that IF THEN ELSE may not be used in a variable expression For example CLE X THEN Y ELSE Z 1 is illegal B 5 CASE EXPRESSIONS Wherever an expression may appear AlphaPascal allows you to include a CASE expression This allows you to conditionally evaluate one of several alternative expressions NOTE This is not a feature of standard Pascal The expression must take the farm CASE value OF valuel expression value2 expression ELSE expression For example WRITECCASE ErrorCode OF 1 ilegal input 2 Number too large 3 Number too small ELSE undefined error EXPRESSIONS Page 8 10 The statement above chooses one string to urite depending on the value of the variable ErrorCode For example if ErrorCode contains a value of 3 the statement above evaluates to WRITEC Number too small 1f rrorCode contains a value that is not 1 2 or 3 the statement evaluates to WRITEC Undefined error CHAPTER 9 STATEMENTS 9
196. in to Largest possible number 3 CurrentMin MAXINT REPEAT READ DataFile NewNumber 7 IF NewNumber CurrentMin THEN CurrentMin i NewNumber UNTIL EOF Continue till end of file is reached gt WRITELN C Smallest number is CurrentMin Pascal allows you to assign a name to a constant so that you can identify it by name within a program rather than including the constant itself For example it would be rather cumbersome if you had to include the numeric constant 3 14159 throughout a program Once you use a constant definition statement to assign 3 14159 a name such as Pi you can refer to that constant by name For example WRITELNC The Circumference Pi 234 You may also assign a name to a string constant For information on naming constants see Section 6 3 Constant Definitions For information on the form string and numeric constants may take see Section 5 6 Notation NOTE Of course constants are not variables that is you may not assign a constant a new value within the program block EXPRESSIONS Page 8 8 8 3 VARIABLES A variable is a named symbol that represents a value For example the variable named StudentID might assume a range of student identification numbers Variables allow a program to operate on 4 variety of data Each variable in a program may assume only one type of value e g integer values real values Boolean values etc Pascal requires that you declare the data type of
197. ing VUE see the AlphaVUE User s Manual DWM 00100 15 Also a brief introduction to VUE is given in Section 2 3 1 of this book Building a Pascal Program After creating your program you will exit VUE and use the AlphaPascal compiler CMPILR which compiles your source program a file that bas the PAS extension into a series of intermediate files Next you will use the AlphaPascal linker PLINK which uses the intermediate files created by the compiler to create a fully resolved runnable P code file that has the PCF extension The linker also allows you to Link together separate files into one program and allows you to update one portion of an existing compiled program without re compiling all of the modules that make up that program To run your PCF file you will use the AlphaPascal run time package PRUN The external library contains a set of procedures variables and functions that are available to your Pascal programs For a List of the routines within the external Library see Section 16 1 STDLIB For information on writing and modifying your own procedures within this library see Chapter 16 Writing and Modifying an External Library File Changed 30 April 1981 OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 2 4 1 FILE AND MEMORY REQUIREMENTS The AlphaPascal system consists of these files DSKO PRUN PRGC1 47 DSKO CMPILR PCFC7 5 OSKO PLINK PCFL7 5 DSKO STDLIA PCFL7 5 DSKO DEMO PAS 7 5 DSK DEMO PCFL7
198. itial FOR value must be of scalar type FOR variable and initial value have incompatible types Tn FOR xi5 x must not be a formal variable In FOR x x must be a non REAL scalar variable GOTO statements are not permitted without G option Definition for this label has already appeared Function calls are not legal as statements Procedure identifier was expected Proc or func too large split it into smaller pieces THEN without IF Undeclared label UNTIL lt expresston gt without REPEAT In WITH x DO x must be a RECORD variable See Chapter 9 for information on accessing record fields with WITH DO WITH statement has caused too many nested scopes xxx Compiler error in STORE You should never see this error message Please report it and the circumstances under which you saw it to Alpha Micro Digit 0 9 expected in exponent assumed missing Unexpected end of source file encountered Remember to end every program or module fiie with a period Digit 0 9 expected in fraction assumed missing Illegal character encountered ignoring Include file not found See Chapter 4 for information on Include Files integer constants must be in the range 32767 Line too long truncated to 132 characters File includes 1 may not be nested Unterminated string multi line strings not permitted In x y both operands must be numeric XXX OF yyy expected inserting xxx XXX Or yyy expected insertin
199. itionally evaluate one of several alternative expressions STATEMENTS Page 9 8 9 8 REPETITIVE STATEMENTS It is often the case that one section of a program must be performed repetitively based on a certain condition AlphaPascal provides a number of repetitive statements WHILE DO REPEAT UNTIL and FOR DO it is important that you decide which of these statements is exactly correct for your application since each differs somewhat in the way that it handles final values 9 8 1 WHILE DO The WHILE DO statement takes the form WHILE Boolean expression DO statement where the Boolean expression evaluates to a TRUE or FALSE and the statement may consist of a compound statement For example PROGRAM VAR Counter Number Average Sum REAL BEGIN Main Program gt Number 1 Average Counter 0 WHILE Number gt O DO BEGIN id WRITELN C Average Average Counter 1 WRITEC Enter number 2 READLN Number 3 Sum Number Average 3 Sum Counter END END Main Program Initialize Number to gt O In effect you tell Pascal While the following condition is TRUE execute the following statements As soon as the condition becomes FALSE the program finishes executing the entire WHILE loop and then goes on to the next program statement It is possible that a WHILE loop will never be executed if the initial condition is not true and never becomes true 9 8 2 REPEAT UNTIL The REPEAT
200. kes no arguments For example PROGRAM TestRND t Generate 20 random integers between 1 and 10 gt VAR I INTEGER BEGIN RANDOMIZE WRITELN C Random numbers between 1 and 10 5 FOR I 1 TO 20 po BEGIN gt WRITELN TRUNC CCRND 10 41 END END Changed 30 April 1981 MATHEMATICAL FUNCTIONS Page 12 6 12 3 13 ROUND X Rounds off xX Accepts a REAL argument returns an INTEGER result For example ROUND 23 78 returns 24 ROUND 23 45 returns 23 12 3 1 SHIFTCX Performs binary multiplication by shifting left the binary representation of the number specified by the first argument the number of places specified by the second argument For example SHIFT 7 2 returns the answer 28 The binary number 111 7 decimal shifted left two places is the binary number 11100 28 decimal X and Y must be of type INTEGER 12 5 15 SQR OXD Computes the square of X For example SGR 8 returns 64 Accepts REAL or INTEGER argument and returns an INTEGER or REAL result 12 5 16 SaRTOO Computes non negative square root of argument Argument may be INTEGER or REAL result is REAL X must be greater than or equal to zero Accepts a REAL or INTEGER argument returns a REAL result 12 35 17 STROO and STR X a b converts numeric values to STRING Accepts a REAL or INTEGER number and returns a STRING You may optionally supply STR with two INTEGER arguments that tell STR how to format a converted number ST
201. l parameters 6 6 4 1 Value Parameters The formal parameters we have seen in our examples above were all used to pass information into the function or procedure When we left the function or procedure the value of the variable we passed into the routine was not actually changed even though it might have been modified within the routine In effect the function or procedure made a copy of the variable and used the coby for its calculations Then when we Left the routine the original value of the variable was unchanged DECLARATIONS AND DEFINITIONS Page 6 12 This type of variable is called a value parameter Value parameters may be variables or expressions 6 6 4 2 Reference Parameters It sometimes happens that you would Like a procedure or function to actually modify a variable Otherwise the only values you could return would be the single value returned by a function To tell a function or procedure not to use a copy of a variable but to use the variable itself include the VAR keyword in front of the parameter For example FUNCTION Justify VAR InputString STRING PageWidth REAL REAL which might modify the string InputString by inserting blanks so that it equaled PageWidth in Length and returns the number of blanks inserted A parameter Like InputString is called a reference parameter Another way of looking at value parameters and reference parameters is that in the case of value parameters we are really deali
202. lare the type of each variable used in a program This chapter discusses the idea of data type and the various data types available in Pascal A data tvpe describes the kinds of values that a variable can assume For example if the variable CustomerID can assume only numeric integer values we say that its data type is integer Some languages allow you to let one variable assume a variety of types For example a variable could have the integer value 34 at one point and the real value 34 56 at another point Pascal on the other hand allows each variable to assume only one kind of data type l Pascal requires that you declare the type of data that a variable can assume This results in several advantages 1 you can always deduce the tvpe of values a variable can assume by reading the program you do not have to run the program to figure it out 2 certain operations may oniy be done on specific data types having to declare your variables aids the compiler in making sure that you are not performing an illegal operation on a variable 3 the compiler is able to make sure that you are not improperly mixing variables of different data types For example you may not multiply a real number by an integer and get an integer result Once a variable has been assigned a data type we have automatically defined the operations that can be applied to that variable the type of values it can assume and the standard procedures and functions that ca
203. lements of an array must be of the same data type Your declaration of the array must include the data type of the elements of the array and the data type of the subscripts by which you will access elements of that array Declaring the type of the subscript tells Pascal how many elements the array will contain For example TYPE MonthTotals ARRAYL1 20J OF REAL The statement above tells Pascal that you are defining an array type named MonthTotals whose elements will be real numbers and that the locations in that array will be accessed by refering to the numbers 1 through 20 e g MonthTotals 1 MonthTotals 2 MonthTotals 201 The subscript data type can be any scalar type except REAL Although this field will often be of type INTEGER it doesn t have to be For example TYPE ComplaintNum ARRAY BobsOffice PaulsOffice OF INTEGER DATA TYPES Page 7 9 where BobsOffice PaulsOffice is a subrange of a user defined scalar type such as RobinsOffice BobsOffice PaulsOffice BillsOffice After you have declared an array type you may now declare a variable of that type For example VAR Problems ComplaintNum Pascal also allows a shorthand form that permits you to combine the type and variable declarations VAR Problems ARRAY BobsOffice PaulsOfficeJ OF INTEGER One of the features that help make arrays so useful is the fact that subscripts may be expressions This allows you to access elements of
204. llowing functions and procedures will be of special use to the experienced AlphaPascal programmer They allow you to determine the Location and size of data objects in memory to determine the amount of free memory Left and to handle system and file errors Other functions and procedures allow you to access system functions such as accessing the Line printer spooler mounting disks reading the system clock and reading setting and releasing multi user file locks 14 1 LOCATION The LOCATION function returns an integer that corresponds to the absolute memory address of the specified variable The invocation takes the form LOCATION variable identifier where variable identifier specifies the variable whose memory address you wish to know LOCATION accepts a variable of any type as an argument LOCATION may not be used on packed fields 14 2 SIZEOF The SIZEOF function returns the size in decimal bytes of the specified item The invocation takes this form SIZEOF variable or type identifier For example SYSTEMS FUNCTIONS AND PROCEDURES Page 14 2 PROGRAM Test izeOf TYPE SampleRecord RECORD character CHAR next SampleRecord END BEGIN TestSizeOf gt WRITELNC Size of SampleRecord in bytes is SIZEOF SampleRecord END TestSize0f J The program above prints Size of SampleRecord in bytes is 4 14 3 MEMAVATL MEMAVAIL returns an integer corresponding to 3 4 the number of unused
205. low we have added notes that give more information about the error and that tell you where to Look in this manual for more information on the operator data structure or declaration involved in the error When CMPILR displays an error message it also displays the line of the program that contains the error and points to the problem For example if you try to compile the following small program PROGRAM TestError VAR Number REAL Number2 STRING BEGIN Try to use addition operator on real and string data IF Number Number2 O THEN WRITELN Zero END you see the following displays Changed 30 April 1981 ALPHA PASCAL COMPILER ERROR MESSAGES Page C 2 AlphaPascal Compiler Version 2 0 lt Da co econ PROGRAM lt S BEGIN Try to use addition operator on real and string data l IF Number Number O THEN WRITELN Zero TLine 6 CBOPNBN In x y x and y are not both numeric HIT RETURN to continue bts T lines 4 10 seconds 102 44 lines minute Total of 1 compilation errors The error above occurred because we tried to perform an arithmetic operation on numeric and string data both Number and Number must be numeric in order to use the addition operator The first eight characters of the error message identify the portion of the compiler that caught the error You will probably not need to make note of this identifier im many of the error messages CMPILR actually substitutes in
206. lude the name of the function within the program block along with the names of the variables that are going to supply that function with data For example to invoke the function SufficientFunds you might include a statement Line like this IF SufficientFunds 100 50 THEN WRITELN C Good check ELSE WRITELNC Sorry overdrawn The statement above prints Good Check if SufficientFunds returns TRUE and Sorry overdrawn if it returns FALSE You may supply variables expressions or constants as the arguments of the function Note that the names of the variables you pass to the function do not have to have the same names as those variables listed in the function heading The first variable or constant mentioned in the function invocation is substituted into the function for the first variable mentioned in the function heading the second variable or constant in the invocation replaces the second variable in the function heading and so on Of course the data types of the variables must be consistent For example if you supply the variable Check to the function SufficientFunds it must contain a number of type REAL Remember that a function invocation is always part of an expression For exampie given the function MaxNum these are valid function invocations DECLARATIONS AND DEFINITIONS Page 6 8 WRITELN The Largest number is MaxNum Number1 Number22 or IF MaxNum Valuel Value2 lt O THEN WRITELN Numbers are negative
207. me type do not necessarily have to contain the same fields Suppose for example that you are maintaining a record of customer information in which one of the fields telis you whether or not the customer has a car D Car Boolean If in fact the customer does have a car you might want to maintain another set of information such as license number model year of make etc but it doesn t make sense to fill in that information for a customer who doesn t have a car Pascal allows you to allocate fields which may or may not exist depending on the value of another field These fields which act as variations to the basic record structure are called variant fieids The variant field definition takes this form CASE field type OF Case labet Case LabelN Case label Case LabelN CField 2tist12 field List2 aa 5m Case l abel Case LabelN field ListND or CASE case field identifier field type OF l Case Label Case labelN field list1 Case label Case labelN fieldelist2 Case label Case labelN field ListN Several case labels may be written on one line separated by commas The List of variant fields must be enclosed with parentheses If no variant fields are to be used in the case of a certain value empty parentheses may be used or the value may be omitted If you create a variant part the variant fields must appear at the end of the record definition For example DATA TYP
208. ming projects Some of Pascal s advantages stem from these characteristics Pascal encourages well structured programming by requiring that programs be built in a block structure in which the beginning and end of each procedure is clearly marked Because program structure is hierarchial in nature programming in Pascal lends itself naturally to top down design One of the most important features of Pascal is its extensibility It is very simple to add your own functions and procedures if the routines provided by Pascal do not exactly match your needs In addition on the AlphaPascal system you can add these user defined routines to an external Library where all Pascal programmers can make use of them Pascal was designed to be a general purpose Language Since it is not specifically aimed at scientific ar data processing applications it can be used to solve a wide range of problems An important feature of Pascal is its powerful data structures arrays sets records pointers user defined etc and the sophisticated structures you can build from those primitives e g linked lists Any variable used in a program must be declared within that program That is Pascal requires that the type of values that a variable may assume e g integer or boolean be clearly stated by the programmer This helps both in program design and maintenance since the readability and organization of your program are enhanced Variables may be
209. mputes the natural Napierian Logarithm Accepts a REAL or INTEGER argument returns a REAL result Computes logarithm to the hase e le 2 71828 12 3 6 10600 Computes the log base ten of the argument Accepts a REAL or INTEGER argument returns a REAL result 12 3 7 00000 Tests for odd value Accepts INTEGER argument returns a BOOLEAN result If X is odd ODD returns TRUE if X is even ODD returns FALSE 12 5 8 POWERC X Y Computes X to the Y power Accepts two REAL numbers returns a REAL result For example POWER 2 0 3 0 returns 8 You can also use POWER to compute the Nth root of a number POWER X 1 0 ND For example to find the cube root third root of 256 12 POWER 256 12 1 0 3 0 Changed 30 April 1981 MATHEMATICAL FUNCTIONS Page 12 5 12 5 9 PWROFTEN OO Returns the value of ten raised to the power of X Accepts an INTEGER or REAL value returns a REAL value Accepts frections and negative numbers For example PWROFTEN C3 returns 10 to the third or 1000 12 5 10 PWROFTWOOO Returns the value of two raised to the power of X Accepts an INTEGER value and returns a REAL value Number must be greater than zero For examples PWROFTWO 3 returns 2 to the third power or 8 12 3 11 RANDOMIZE Randomizes the starting seed of the RND function see below It takes no arguments For example RANDOMIZE 12 5 12 RND Returns a random REAL number between O and 1 It ta
210. n 7 2 7 RECORDS Use the type declaration to declare the data type TYPE identifier FILE OF base type where identifier is the name you want to assign to that type of file and base type is the data type of the data in the file To use this type of file you will have to define a variable of that type VAR file identifier identifier DATA TYPES Page 7 16 The file identifier acts as a communication channel Using commands such as OPEN see Section 10 2 12 OPEN O you can associate the file identifier with an actual AMOS file and transfer data between your program and the disk file Rather than using a type declaration followed by a variable declaration AlphaPascal also permits you to use a shorthand method of combining type and variable deciaration statements VAR NewData FILE OF INTEGER Remember that you must use one of the functions or procedures discussed in Chapter 10 I O Functions and Procedures to tell AlphaPascal which AMOS file you want to associate with the file variable that you have declared NOTE The chapters in this book especially Chapter 10 frequently use the term file identifer Other books that describe Pascal may just call this identifier file The file identifier is not the same thing as a file specification The file specification identifies the actual AMOS disk file that vou want to read data from or write data to The file identifier identifies the Pascal file variable Think of the
211. n be used on it several data types have been pre defined for you by AlphaPascal these are called standard data types The AlphaPascal standard data types are INTEGER REAL BOOLEAN CHAR STRING and TEXT Data types are grouped into two categories simple and structured A simple data type is a scalar type A scalar data type is one that contains a set of elements and those elements are ordered For example the INTEGER data type contains the set of whole numbers These elements are ordered for instance 2 is less than 1 which is less than O which is less than 1 which is less than 2 and so on DATA TYPES Page 7 2 Structured data types are more sophisticated than the simple scalar data types Tf you were to create your own structured types they would be made up of simple data types Pascal supplies a set of keywords SET ARRAY RECORD and FILE that you can use to build str ctured types 7 1 SIMPLE DATA TYPES Simple data types can either be the pre declared simple data types INTEGER REAL BOOLEAN and CHAR or they may be types defined by you 1f defined by you a simple data type is either scalar type or a subrange of another already defined scalar data type 1 1 INTEGER Integers are whole numbers that is numbers with no fractional part AlphaPascal allows you to use integers in the range of 32767 through 32767 They are stored by the computer as one word signed 2 s complement binary numbers These are in
212. n with the file identifier before using CREATE You may use FSPEC SETFILE or OPEN with the RANDOM mode to do so For example PROGRAM RandomFile VAR RanFile FILE OF STRING Counter INTEGER BEGIN RandomFile gt Counter is FSPEC RanFile NEWFIL DAT 2 CREATE RanFile 20 END RandomFile The program above creates the 20 block random file NEWFIL DAT The FSPEC function assigns the filespec NEWFIL DAT to the file variable FILE RanFile NOTE CREATE causes an error if the file you are creating already exists or if there are not enough contiguous blocks available for it to be allocated INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 19 on the disk If you wish to create a random file capable of holding X records of type T then the number of biocks it will require is 1 X DIV 512 DIV SIZEOF T 10 2 4 ERASE The ERASE procedure erases a file from the disk The invocation takes the form ERASE Cfile identifier where file identifier is the file variable associated with the AMOS file you want to erase ERASE does not return an error if the specified file is not there This makes it very useful for ensuring that the creation of new files wili be successfully carried out For example since CREATE see above and OPENO return an error if the file you want to create already exists you can use ERASE before using OPENO or CREATE to make sure that the file you want to open does not already exist I
213. nation with ten A s 13 2 2 MOVELEFT and MOVERIGHT The MOVELEFT and MOVERIGHT procedures move blocks of bytes in memory They can be dangerous if not used correctly For example if you tell one of these procedures that you want to move 20 bytes but the destination array only contains 10 bytes where do the extra 10 bytes go Somewhere in memory You will probably use MOVELEFT and MOVERIGHT most often to shift characters within a single array You can also use them to move characters from one array of type CHAR to another MOVELEFT starts at the left of the specified source array and moves bytes to the specified position in the destination array also beginning at the Left MOVERIGHT moves bytes beginning with the right of the source array STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 8 and beginning with the right of the specified locations in the destination array You specify the source array the destination array and the number of bytes to move In the case of an array Of type CHAR one byte is one character By including subscripts you may Specify the Locations in the source and destination arrays at which to start Of course MOVELEFT and MOVERIGHT do not physically move the bytes instead they make a copy of the specified bytes from the source array into the specified Locations of the destination array The invocations of MOVELEFT and MOVERIGHT take this form MOVELEFT Source array Destination array N
214. nction or procedure or your program when any error occurs Of course you can only EXIT to Leave a function or procedure which is currently active so you will probably want to have around some BOOLEAN variables to keep track of whether or not you are currently within routines which you might wish to EXIT from ERRORTRAP 3 Remember to set XEQERR back to zero before leaving ERRORTRAP otherwise your next error will abort to AMOS without calling ERRORTRAP 14 10 53 XERRORTRAP When STDERRORTRAP is called by entering a Control C it is possible to request a backtrace of suspended functions and procedures This backtrace begins with the caller of the caller of STDERRORTRAP which is usually the caller of ERRORTRAP and hence the routine which was suspended Thus should STDERRORTRAP be called by a function or procedure local to your ERRORTRAP procedure the backtrace will begin in the wrong place This can be corrected by using XERRORTRAP which takes a copy of the system INFOREC as its argument It is used as follows SYSTEMS FUNCTIONS AND PROCEDURES Page 14 16 PROCEDURE ERRORTRAP VAR INFOP INFOREC INFO INFOREC PROCEDURE P1 BEGIN XERRORTRAPCINFO END BEGIN INFOP ERRORINFO INFO INFOP P1 INFOP XEGERR s INFO XEQERR END Using XERRORTRAP the backtrace will be displayed beginning with the caller of the routine which invokes ERRORINFO thus producing a correct backtrace even when called from an inner
215. nd to give hints on converting programs written in these versions of Pascal to the current AlphaPascal format and 5 To give operating instructions for the various components of the AlphaPascal programming system the compiler the linker and the run time package This book also gives information to systems programmers on writing their own assembly language subroutines callable by Pascal programs and on writing and modifying an external procedure library INTRODUCTION Page 1 2 1 1 ORGANIZATION OF THIS BOOK Some of the chapters in this book are aimed at experienced Pascal programmers while others are specifically for new Pascal users To help you find the information that you are particularly interested in we have divided this book into four general parts PART 1 THE ALPHA PASCAL SYSTEM PART II SUMMARY OF ALPHA PASCAL PART III ADVANCED PROGRAMMING ON THE ALPHA PASCAL SYSTEM PART Ivy D APPENDICES The rest of this section discusses which chapters may be of particular interest to specific readers IF YOU ARE AN EXPERIENCED PASCAL PROGRAMMER You will probably want to skip Chapter 2 Getting Started and go directly to Chapter 3 Compatibility and Conversion which tells you how this version of Pascal differs from earlier versions of AiphaPascal and from the Jensen and Wirth standard Chapter 4 discusses how to operate the various components of the AlphaPascal programming system Rather than read through Chapters
216. ng with two different sets of variables those outside the routine and those inside In the case of reference parameters we are dealing with only one set of variables Reference parameters must be variables 6 7 EXTERNAL DECLARATIONS AlphaPascal provides an external Library of procedures and functions This collection of useful routines is available for use by your program You may also write your own external libraries To teli AlphaPascal that you are going to use a function or procedure that is in a standard Library other than STDLIB you must precede the declaration of that function or procedure with the keyword EXTERNAL For example EXTERNAL FUNCTION Graph X Y REAL REAL RN AN emi ian EAS Ori EXTERNAL PROCEDURE PrintLine Line STRING You do not include the procedure block or function block since the actual definition of the routine is in the external library Besides identifying procedures and functions within your program that are defined in an external library you will use the external declaration to designate elements that appear in files that are not a main program file For example suppose you have a main program file and three other files which will be Linked together to form one program See Section Dad Pragram Structure for information on main program and non program files Within one file vou may well want to use a procedure function or variable that was declared and defined in another file I
217. ng like this ERASE SALARY PCF ANo files deleted PRUN PLINK AlphaPascal V2 9 Code file SALARY Creating new code file SALARY PCF Library code file for SALARY PCE STDL IB Please specify files to be linked into SALARY one per Line ending in a blank Line File 1 File 2 Loading program and Library dictionaries Processing SALARY Linking in global func proc PROGRAM Transferring temporary file to new code file SALARY completed SALARY Ho The first thing that the command file does before Linking your file is to erase any file SALARY PCF that already exists This is because PLINK asks different questions depending on whether or not the specified program already exists and we want to make sure that PLINK asks a particular set of questions Now it invokes PLINK For more information on linking a file see Section 4 4 The ALphaPascal Linker That section also discusses the meaning of the display vou see above and talks about the concept of a library 2 5 3 Running a Pascal Program To run the program vou have compiled use the Pascal run time package PRIN At AMOS command level enter PRUN SALARY PCF RET followed by a RETURN At last your program is running For full information on executing Pascal programs refer to Section 4 5 The Changed 30 April 1981 GETTING STARTED l Page 2 9 AlphaPascal Run time Package As you run SALARY PAS you see AlphaPascal V2 0 What is your gross
218. nguage routine you will probably want and need temporary data areas There is no room for allocating memory modules for this purpose Instead you may either allocate space for data in the SP stack or place your data inline in your routine this is unacceptable far routines which are to be loaded into system memory since they must be sharable The R5 stack is NOT available for allocating data space Another method for obtaining larger data areas is to have your caller pass them to vou as arguments 15 5 RESTRICTIONS As mentioned above there is no room for allocating memory modules This also means that you may not use INIT to create a file buffer or perform file operations which would require Loading a device driver into memory CHAPTER 16 WRITING AND MODIFYING AN EXTERNAL LIBRARY When you link together your programs using PLINK you are asked to specify a Library file Typically you specify STDLIB The global functions procedures and variables contained in this Library are available to you just as if you wrote them in a module and Linked them into your program However using routines contatned in a Library requires no additional space in your program s code file because the routines are accessed directly from the Library file at run time There are several advantages to placing commonly used routines in a Library rather than Linking them directly into your program First you save disk space by only having a single cop
219. nies this release of AlphaPascal The PCL command file compiles and Links a Pascal source file Suppose you supply to PCL the name of a source file that does not exist If the compiler can t compile your program then PLINK can t link it So CMPILR itself contains a KILCMD procedure call that is executed if a compilation fails the system stops any command file being executed and returns you to AMOS command level For information on error handling and writing your own errortrap routine see Chapter 14 Systems Functions and Procedures 17 1 3 MARK MARK is used in combination with RELEASE to store and release dynamic variables allocated via NEW see below in a stack Like structure called the heap The invocation of MARK takes this form MARK vartable identifierd where vartable identifier specifies a pointer variable that points to any type typically INTEGER MARK returns the current state of the heap That is it returns the current address of the top of the heap MISCELLANEOUS FUNCTIONS AND PROCEDURES Page 11 3 A heap or Stack can be considered as a sequential List in which items may only be inserted or deleted from one end of the List Items are deleted in the reverse of the order in which they were entered on the stack The NEW procedure allocates dynamic variables on the heap For example if you use MARK then perform a NEW then use MARK again MARK will return two different values since the top of the heap
220. nk a program using the SMASH option users of that program are prevented from seeing the names of the program s procedures and functions when they backtrace the program instead the names are replaced with asterisks For example instead of the backtrace display Interrupt Help B in STDLIB PCF RDR at IPC 33 in VALID PCF PROGRAM at IPC 43 In STDLIB PCF PROGRAM at IPC Exit to AMOS 423 H they see OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 17 Interrupt Help 8 GEF in STDLIB PCF RDR at IPC 33 In VALID PCF kekekedeekk at IPC 43 In STDLIB PCF PROGRAM at IPC 423 Exit to AMOS Note that in the smashed version above the name of the function in your own program VALID PCF is blanked out with a Line of asterisks To use the SMASH option place the option request after the name of the code file you want to smash For example Code file VALID SMASH When PLINK finishes Linking the specified files it tells you that the names of the functions and procedures in the code file have successfully been hidden from the backtrace option In the case of the file discussed above VALID PCF vou see SMASHed VALID SMASH Completed NOTE CMPILR and PLINK have both been linked using the SMASH option 4 5 THE ALPHA PASCAL RUN TIME PACKAGE The AlphaPascal run time package PRUN is the program that executes your program by interpreting the PCF file created by the Linker To use PRUN at
221. nto another string Returns number of characters in string Converts upper case string to lower case Returns position of specified character in string Removes trailing spaces from string Converts Lower case string to upper case Converts a string to a REAL number For data of type PACKED ARRAY OF CHAR FILLCHAR MOVELEFT MOVERIGHT SCAN Filis specified string with specified character Copies specified number of characters beginning with Left of array over to specified array Copies specified number of characters beginning with right of array over to specified array Returns position of specified character 3n array Changed 30 April 1981 arrays STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 2 13 1 STRING INTRINSICS Below are the functions and procedures that you can use on data of type STRING 13 1 1 CONCAT The CONCAT function returns a string that contains the contents of all of the specified string s The function invocation takes this form CONCAT Stringi String2 StringND where you may specify one or more strings to be concatenated For example PROGRAM TestConcat VAR Destination Sourcel Source2 Source STRING BEGIN TestConcat gt Source Nevermore Source2 the Raven Sources Quoth Destination CONCAT Source3 Source2 Source1 WRITELN Destination END TestConcat The program above prints Quoth the Raven Nevermore 15 1 2 COPY T
222. nto Charmode suppresses echoing LINEMODE Returns terminal from Charmode to line mode INCHARMODE Returns Boolean value telling you whether you are in Charmode or not 11 1 BASIC FUNCTIONS AND PROCEDURES 11 1 1 CHR ALL characters displayed by the computer are members of the ASCII character Set and have a number called the ASCII value associated with them The CHR function returns the ASCII character associated with a specified ASCII value It accepts a positive decimal INTEGER argument and returns a CHAR result The function invocation takes this form MISCELLANEOUS FUNCTIONS AND PROCEDURES Page 11 2 CHR number For example WRITELN CHR 65 prints the character A 65 is the decimal ASCII value of the ASCII character A 11 1 2 KILCMD It is often convenient to set up command files that automatically invoke a series of system commands and Pascal programs Remember that a command file is a text files each line contains data or a valid AMOS file specification To execute the entire set of tommand and program invocations contained in the command file supply just the name of the command file at AMOS command Level The KILCMD procedure tells PRUN to abort any command file execution You probably will use KILCMD if an error occurs that would make continuing the execution of the commmand file awkward The invocation takes this form KILCMD As an example of the use of KILCMD consider the command file PCL that accompa
223. number is larger than 12 digits the number will be printed in scientific notation If the fractional part of a REAL number is greater than 11 digits that number will be printed in scientific notation INTEGER numbers are printed as a sequence of digits possibly preceded by a minus sign INTEGER numbers are not printed with a leading space REAL numbers are printed with a leading space unless the number is negative in which case the minus sign takes up that space REAL numbers are accurate to nearly 12 digits They are always rounded to 11 digits before being displayed to avoid annoying outputs such as 4 9999 instead of 5 Both WRITE and WRITELN allow you to include optional arguments that give additional formatting instructions to AiphaPascal The farm of these arguments is for both WRITE and WRITELN WRITE expressionl X Y expression2 X Y 5 where X specifies a minimum field width and Y specifies the number of digits to write after the decimal point X and Y must both be of type INTEGER and may be constants or variables If you are not printing a REAL number you may not specify the Y argument The minimum field width specifies the minimum number of spaces in which the number is to be printed For example if you want AlphaPascal to print the number right justified in a field of ten spaces use the value 10 for X This gives the minimum field in which to print the number if the number is larger than the specified
224. numbers co s o o a a 59 10 10 Changed 30 April 1981 ALPHA PASCAL USER S MANUAL Page Index 8 RECORD s sn n o o n 2716 15 5 Record variants s a a s o a 18 Recursion en on W9 Reference parameter s s es 6 12 15 3 Registers n s a sono a no a a a n o 1572 Relational operator s s a 876 e ee C A RENAME aaa DB ARUGA Erde N0227 REPEAT UNTIL as fe Reserved words soa a e e a o Ir 5 5 to 5 6 RESET 4 qx as a TORTS REWRITE a a 2 ww ss 10 13 p AREE c cs BOUND A ow cee ca ey ww 2026 Running a program a s e s o ua 278 Sample program NEPAL a Si a de ec eae TE Demonstration e a wo CT Hi E STORE ERRORTRAP o a ao ao so a o a o 14712 Formatting output eet ar A Forward destacaron ls 6210 FUOSETON lu Curae A a a GET and PUT w w a s a mano GETFILE and SETFILE a a i IN O e i oO Op os eae NG m COTOS eulx we ae wwe s Ux a e 6 2 Identifier Scope a uu s a a 5 9 IF THEN in expressions a s 379 Linked List s a s waa wa 7721 Modifying assignment operator 8 5 Mathematical functions a e 312 7 Pointers e a w a Grow ox 80 Random file a a s s s a e 10 29 REPEAT UNTIL aa x s s a a a 99 Sets DD maan a a AS WHILESDO ar a at in cw o 48 Scalar constant Loo ius 79 Scalar data type a a mona Prt 775 SCAN AU er ee a ees e SATO Scientific notation e s s uman 5 10 Scope of ident
225. o o ae 18 4 tata REAL a a 15 4 18 2 20 STRING ae al Aa sa 1974 15 2 2 7 Pointers e NOTE 15 4 Sd SOUS bina aaa Pa uw ALAT 15 4 15 2 2 9 ArrayS sennen a E e 75 2 0 T Records ra a 15 5 19 2 20 A A CR AR EN 15 5 194213 Error Ext a e as ax 1972 15 3 CODE RESIDENCY uiu Rok mman ROC om aa ATA 15 5 15 3 1 Routine PLINKed with LINK Naay LTD 15 3 2 Routines PLINKed without LINK 15 6 15 4 OBTAINING MEMORY FOR DATA AREAS S era RI 15 6 1575 RESTRICTIONS pray navora niesna EE E EE 15 6 CHAPTER 16 WRITING AND MODIFYING AN EXTERNAL LIBRARY 16 1 STDLIB ld ew do ecw ea aw ie iaa AREA Rib iN MUS exe 1672 16 2 WRITING LIBRARY FILES Viera as ARO 16 5 MODIFYING STDLIB ceo ocaanonozo PUT naa 16 74 16 4 VERSION CHECKING ssaasesasanasesonsaa aa qute ORO Changed 30 April 1981 ALPHA PASCAL USER S MANUAL Page x PART IV APPENDICES APPENDIX 4 QUICK REFERENCE TO ALPHA PASCAL A 1 PROGRAM STRUCTURE cece ncn acueuun ao naaa aaa AG A 2 DECLARATIONS AND DEFINITIONS Ka hh AA A 2 1 Label Declarations eh ansnaocassenroasesues AT 4 2 2 Constant Definitions DE A 2 5 Type Definitions ara as NATA A 2 4 Variable Declarations r ooooooonooo sa AnI A 2 5 Procedure Declarations cscecccacaccace A 3 A 2 6 Function Declarations gis ease Rue Aex A 3 DATA TYPES wacwnuunnvancaucecuae 3 9 ar IW EORR sas Ari A 5 1 Simple Data Types lces eene ences AMS A 3 1 1 Standard Data Types Ark
226. o ways to generate subprograms which may be called upon wherever needed in a program These subprograms are called functions and procedures Such subprograms also help you to maintain your programs since if a change must be made it only needs to be made once Althaugh you may invoke these functions and procedures any place in the statement part of your program or within the declarations of other functions and procedures you must first define the functions and procedures within the declaration part of your program before you invoke them A special case exists for referencing functions and procedures within other functions and procedures before they have been defined see Section 6 6 3 Forward beclarations Functions and procedures can be thought of as programs within a program They can declare variables define and invoke procedures and functions of their own known as local procedures and functions and input and output data 6 6 1 Functions A function is a subprogram that performs some computation and returns a value For example the standard function ABS takes a number and returns the absolute value of it Pascal allows you to define your own functions by including function declarations at the front of the program or procedure that will call that function Function declarations must appear after any variable declarations The function declaration takes this form FUNCTION function name formal parameters dat
227. ocessRequests Changed 30 April 1981 INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 38 PROCEDURE Termination BEGIN CRT C 1 00 Clear screen WRITELN Leaving AlphaPascal Random File Demonstration END Termination BEGIN Program Introduction ProcessRequests Termination END Program 10 3 3 Program Organization We would just like to point out that the program above could have been broken up into modules and Linked as separate files In fact it would have been a good idea to do so If we were going to break it up we might consider taking the first tuo global type declarations and putting them into include files see below For information on include files see Section 4 5 2 2 The Include Option 1 Then we might have made the FIND function a module FIND PAS 10 3 3 1 The AMOS file NAMREC INC TYPE NameRecord RECORD First STRING 111 Middle CHAR Last STR NGC157 END NameRecord te 10 3 5 2 The AMOS file EMPREC INC TYPE EmpRecType Control Data Unused EmpRecord RECORD CASE EmpRecType OF Data Name NameRecord Age INTEGER Sex Male Female NextDataRecord INTEGER Control FirstDataRecord ARRAY C A Z OF INTEGER FirstUnusedRecords INTEGER Unused NextUnusedRecord INTEGER END EmpRecord EmpFileType FILE OF EmpRecord Changed 30 April 1981 INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 39 10 3 3 3 The AMOS file FIND PAS
228. of Languages Pascal is a fairiy new programming language and is considered by many to be cleaner and more powerful in design than many older Languages as well as more reflective of current trends in the philosophy of program design and structure However this does not mean that programs written in Pascal will necessarily be clearer or more powerful than programs written in other Languages that will depend on the programmer The major claim made for Pascal is that the language makes it easier to write programs that may be easily understood and maintained lt was developed in response to increasing concerns that current programming languages were not encouraging good programming style and is based on the idea that an effective programming language should help the programmer to apply design techniques in a natural and simple way The result should be well made well structured programs that are easy to read and easy to GETTING STARTED Page 2 2 maintain Because most of a program s life cycle is spent in design and maintenance the creators of Pascal tried to develop a language that heips programmers in these areas Pascal s use acceptance and availability have become widespread in recent years An increasingly large number of students are being taught Pascal as their first programming Language Pascal s use in industry is also becoming more prevalent as project planners become more aware of its usefulness in implementing Large program
229. of characters in the array from the beginning of the array until the specified character If the specified Characters are not found SCAN returns the number of characters in the entire array The function invocation takes this form SCAN Length Partial expression Source array where Length gives the Length of the array Source array specified the packed array of type CHAR that is to be searched and Partial expression takes the form lt gt character expression character expression For example PROGRAM TestScan VAR Source PACKED ARRAY 1 25 OF CHAR BEGIN TestScan 7 Source Error 30240 type RETURN WRITELN C Error code starts after char SCAN 25 Source END TestScan gt If the searched for character expression is the first character of the array SCAN returns a zero By specifying a negative length you can tell SCAN to scan the array backward from right to left If the specified character appears in the array SCAN then returns a negative number specifying the number of characters scanned from the right of the array before the specified character was reached If you supply a negative length be sure to alsa specify the position in the array at which you wish the search to start For example WRITELNC It starts after character SCAN 25 Sourcel25 PART III ADVANCED PROGRAMMING ON THE ALPHA PASCAL SYSTEM CHAPTER 14 SYSTEMS FUNCTIONS AND PROCEDURES The fo
230. of the error and aborts to AMOS Whenever a user types a Control C while his program is executing execution is Suspended and the user is allowed to choose among a series of options such as resuming his program exiting to AMOS or displaying a backtrace of suspended function and procedure invocations However it is not always desirable to Let the system perform error handi ing for you You may wish to allow the user to type a Control C in order to exit from some mode of a program or in order to obtain a status report on the progress of your program in processing some task It may be that you have an applications package in which the users of your package are unfamilar with AMOS if an error occurs you may simply wish to print a message and return to the top level of your applications package Or it may be that you enforce security on your system and have an unattended program that you wish to LOGOFF automatically if an error occurs For these reasons and more it is desirable for you to be able to write your own routine to handle a Control C and error conditions AlphaPascal allows you to do so and the remainder of this section will attempt to provide you with the necessary information to write such a routine 14 10 1 Including ERT INC In order to write your own error reutine you must include a special set of definitions with I ERT boing so includes the following text TYPE C CI INFOREC RECORD XEQERR INTEGER FILERC INTEGER
231. ogram heading is syntactically correct For example PROGRAM NewAccount generates an error message because of the open parenthesis The program block which appears under the heading consists of a declaration section that defines the names and properties of various data objects such as variables and constants and subprograms such as procedures and functions that will be used in the program and a statement section which GENERAL INFORMATION Page 5 2 lists the actions to be taken upon the declared items The names of the data objects as well as the names of the procedures and functions af a Pascal program are called identifiers The program block takes this form Label declaration part Constant definition part Type declaration part Variable declaration part External declaration part Procedure and function declaration part Statement part For information on the definition and declaration sections of the program block see Chapter 6 Declarations and Definitions For information on the statement section of the program block see Chapters 9 13 Any number of spaces and or blank tines may appear between words and symbols in a Pascal program Because program statements may be broken up by blank Lines and spaces Pascal requires that you identify where one statement ends and another begins by separating them with a semicolon For example PROGRAM NewTest VAR Counter REAL The last element of a Pascal program must be th
232. on or in scientific notation These are real numbers wg 9 5 56 7812 7 03E 5 45 0 1a 03E 3 The computer stores real numbers as three word floating point numbers significant to 11 digits 12 for real numbers in which the fractional part is zero or less than TE12 with an exponent range of roughly 1E 37 to 1E37 The standard identifier REAL designates the real number data type For example VAR Mean Median Variance REAL The operators defined for real numbers are addition subtraction and sign inversion multiplication real division and the relational operators Many functions accept REAL numbers as arguments Note that you may not use the PRED and SUCC functions or the set membership operator IN on REAL data 7 1 3 BOOLEAN The Boolean data type contains two elements TRUE and FALSE These elements are ordered so that FALSE lt TRUE And SUCCCFALSE returns TRUE FALSE and TRUE are pre declared constants A Boolean variable represents a logical true or false value For example IF Month April THEN Spring TRUE In the statement above Spring is a Boolean variable that can assume the values TRUE or FALSE To designate a Boolean data type use the standard identifier BOOLEAN For example VAR Query Female Employee BOOLEAN The operators defined for Boolean data are AND OR and NOT These are called Boolean operators and produce a Boolean result For example DATA TYPES Page
233. open and close sequential and random AMOS files The functions and procedures we discuss in the following sections are LOOKUP Searches for specified file returns Boolean value OPEN Opens file in input output or random mode OPENT Opens fiie in input mode OPENO Opens file in output mode OPENR Opens file in random mode CLOSE Closes file associated with specified file identifier FSPEC Returns number of characters in filespec associates filespec with file identifier EXTENSION Forces specified extension into file specification GETFILE Reads information in file specification SETFILE Places information into file specification CREATE Allocates random file blocks SEEK Positions random file to specified file record ERASE Erases specified file from disk FILESIZE Returns number of disk blocks used by file JOBDEV Returns device user is Logged into JOBUSER Returns account user is logged into PFILE Prints name of file associated with specified channel RADSO Converts threercharacter string to RADSO format RENAME Renames specified file 10 2 1 Information on AMOS Files The AMOS file system recognizes two major types of files random and sequential Creating opening and performing 1 0 for the two types of files differs somewhat so it is important to understand the differences between them Before we discuss AMOS disk files we would Like to mention again that the precdeclared file identifiers INPUT OUTPUT and KEYB
234. or example in the example above Violet is O Blue is 1 and so on You may not use scalar types in 1 0 operations For example this statement is illegal WRITECYellow if Yellow is an element of a user defined scalar type However you could say something Like IF Colors Yellow THEN WRITE Yellow Note that Colors is a variable but Yellow is a constant of the scalar type Spectrum just as the number is a constant of the scalar type INTEGER You may only use relational operators and the set membership operator IN on an element of a user defined scalar type NOTE Rather than using a type declaration followed by a variable declaration you may combine both statements into one variable declaration when defining your own data types For example VAR WaveLengths Colors Wiolet Blue Green Yellow Orange Red DATA TYPES Page 7 6 However if you are going to have more than one variable declaration that declares variables of that type you must have a separate type declaration statement instead You may use the ORD PRED and SUCC functions on user defined scalar types For example given our example above ORD Vialet 0 ORD Blue 1 SUCC Violet Blue PRED Orange Yellow 7 1 6 User Defined Subrange Pascal allows you to define a subrange of a previously defined data type For example given the data type Spectrum above suppose you want a variable to only access the first three colors elements of that typ
235. ou write are rezentrant you may load them into system memory If you should run out of room in memory while compiling a program CMPILR displays the messages insufficient memory o kad Attempt to call ERRORTRAP while in ERRORTRAP 4 2 CREATING A PASCAL PROGRAM To create a Pascal source program use one of the system text editors VUE or EDIT If you are using a video display terminal you will probably want to use the screen oriented text editor VUE For a full description of how to use VUE and a list of all of its commands see the AlphaVUE User s Manual CDWM 00100 15 Also Section 2 5 1 Building a Pascal Program of this book contains a brief introduction to VUE 4 3 THE ALPHA PASCAL COMPILER The compiler reads the source program that you have created and compiles it into three intermediate files that have the same name as the source program file and the extensions P01 PO2 and P03 These files are used by the Linker to create the final executable program file which has a PCF extension Tf POT PO2 and P03 files already exist with the same name as the program CMPILR deletes them before compiling the new source program i To use the compiler at AMOS command level enter PRUN CMPILR RET The compiler now asks you for the name of the source file AlphaPascal V2 0 Source file name Enter the name of the file that contains the program or module you want to compile followed by a RETURN CMPILR assumes th
236. out this is if you use expressions that compare unparenthesized Boolean expressions with relational operators e g NOT A BD If your programs must be written to be compatible with standard Pascal for instance if you want to be able to transfer your programs to another computer system that uses standard Pascal use parenthese to make sure that your expressions are evaluated in accord with standard Pascal s rules of operator precedence For example the expression NOT A B is evaluated by AlphaPascal as NOT A ED lf vou want the expression to work for either standard Pascal or AlphaPascal you should either write it ass NOT AD B or NOT LA BD to indicate how you wish the expression to be evaluated a The table below gives the rules of operator precedence for AlphaPascal EXPRESSIONS Page 8 3 ui Highest Precedence Parenthesized expressions Sign inversion unary Multiplying operators f DIV MOD Adding operators Relational operators lt gt lt gt C gt IN Boolean operators NOT AND OR Lowest Precedence 8 1 2 Assignment Operator The assignment operator 5 assigns the value of an expression to a variable See Section 9 1 Assignment Statement for information on its use in a program statement Pascal evaluates the expression on the right side of the assignment operator symbol t9 The variable on the left side of the assignment operator then assumes the value of that expre
237. ployeeInfo EmpFile RecNum EmpFile NextDataRecord Count 1 END END WRITELN WRITELN Total of Count employee s END ListEmployees PROCEDURE AddEmployee VAR Employee EmpRecord BEGIN GetName Employee Name IF Find Employee Name THEN BEGIN WRITELN Employee already on file EXIT AddEmployee END GetEmployeeInfo Employee IF NOT Add Employee THEN WRITELN Not enough room to add END AddEmployee Page 10 36 INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 37 PROCEDURE ChangeEmployee c VAR Name NameRecord BEGIN Get Name Name IF Find Name THEN BEGIN ShowEmployeeInfo EmpFile GetEmployeeInfolEmpFile 7 PUT CEmpFite s END ELSE WRITELNC Not found END ChangeEmployee PROCEDURE DeleteEmployee VAR Name NameRecord BEGIN GetName Name IF NOT Remove Name THEN WRITELN Not found END DeleteEmployee PROCEDURE Inquire VAR Name NameRecord BEGIN Get Name Name IF Find Name THEN ShowEmployeeinfo EmpFile ELSE WRITELN Not found END Inquire Go BEGIN ProcessRequests REPEAT WRITEC Enter option A dd C hange Delete Dnquire List Quiti READLNCOpt ion CASE Option OF a PA s AddEmployee tet C ChangeEmployee d p DeleteEmployee a I Inquire L L s ListEmployees gi p Q s EXIT ProcessRequests ELSE WRITELNC Invalid option WRITELN UNTIL FALSE 1 e until EXIT END iPr
238. r several in the case of the CASE OF expressions IF Boolean expression THEN expression ELSE expression and CASE value OF value expression value2 expression sem valueN expression ELSE expression A 5 STATEMENTS Statements are either simple statements or structured statements A simple statement consists of only one statement Structured statements are comprised of more than one statement You may Label statements by writing Label statement where Label is an unsigned integers gt A 5 1 Simple Statements The Pascal simple statements are A 5 1 1 Assignment Statement assigns a value to a variable variable expression A 5 1 2 Procedure Call Procedure calls invoke the specified procedure and take the form procedure name procedure parameterl parameter parameterN QUICK REFERENCE TO ALPHA PASCAL Page A 10 A 5 1 3 GOTO Statement The GOTO statement transfers program control to the Labeled portion of the program It takes the form GOTO Label A 5 1 4 Null Statement Another permissible simple statement is the null statement that Ts no statement at all A 5 2 Structured Statements The Pascal structured statements are 4 5 2 1 Compound Statements The compound statement is bracketed with the keywords BEGIN and END and takes the form BEGIN statement1 statement2 statementN END amp compound statement may take the place of any single statement in the
239. racter at a time even before a terminating carriage return is typed Assembly Language programmers on the AMOS system may recognize this input mode as image mode The invocation of this procedure takes this form CHARMODE Character mode is useful for checking special input such as passwords since the characters are not echoed at the time they are input but when read via a GET or READ To inhibit echoing use the pre declared KEYBOARD file identifier NOTE Character editing such as RUBS or Controi lis doesn t work when the terminal is in character mode To return a terminal to the normal mode use the LINEMODE procedure discussed in Section 11 2 3 below When your program exits to monitor level AMOS automatically puts the terminal back into LINEMODE MISCELLANEOUS FUNCTIONS AND PROCEDURES Page 11 7 11 2 2 CRT The CRT function allows you to position the cursor on the terminal Screen In addition you can also select certain terminal handling options such as clear screen delete character etca The function invocation takes this form CRT CArg1 Arg25 where Arg and Arg are integers If Argi is positive the CRT function assumes that you want to position the cursor on the screen if Arg is negative CRT assumes that you want to use one of the extended screen handling options 11 2 2 1 Cursor Positioning If the first argument you supply to CRT is positive then the CRT function reads both argument
240. ram will be put to sleep until it becomes available When XLOCK returns to the user program RETCODE will contain a O if the Lock was allocated or the user s job number if the lock already was allocated to him 14 6 4 Clearing a Lock After a lock is no Longer needed i e in the above example moving to another record it must be cleared so that other users have access to that Lock To clear a Lock the CLEARLOCK mode is used Again using the above examples RETCODE XLOCK CCLEARLOCK LOCK1 LOCK2 SYSTEMS FUNCTIONS AND PROCEDURES Page 14 8 RETCODE will contain the number of locks that were cleared If RETCODE 0 after the call then no locks were cleared If RETCODE 1 then one lock was cleared If RETCODE gt 1 then a wildcard was specified in LOCK1 or LOCK2 and mucho locks were cleared 14 6 5 The GETLOCKS Subroutine GETLOCKS is an external procedure Therefore it must be specified as such in the Pascal program that uses it EXTERNAL PROCEDURE GETLOCKS VAR LOCKQTY JOBNUM INTEGER VAR LOCKARRAY LARRAYO Type LARRAY is an array of type LOCK LOCK is set up as follows TYPE LOCK RECORD JOB LOCK1 LOCK2 INTEGER END If X is a variable of type LOCK then X JOB is the job number that holds the Lock X LOCKT and X LOCK2 are the lock valued of the lock LARRAY is defined as follows TYPE LARRAY ARRAYI1 25 OF LOCK The variable LOCKARRAY may then be allocated for GETLOCKS to return the list of locks in VAR
241. ring and listing of multi user file locks like the equivalent BASIC subroutine XLOCK In fact the Locks set by the Pascal XLOCK are the same as those set by the BASIC XLOCK This means that Pascal and BASIC programs can be used to lock each other out For a Lengthier discussion of the concept of file Locks refer to FLOCK BASIC Subroutine to Coordinate Multi user File Access DWM 00100 16 and XLOCK BASIC Subroutine for Multi User Locks DWM D0100 112 in the BASIC Programmer s Information section of the AM 100 documentation packet Briefly however a fiie lock is merely a convenience that allows a program SYSTEMS FUNCTIONS AND PROCEDURES Page 14 6 to check to see if a current file is in use The reason for file locks is that multiple users will destroy the contents of a file if they access it at the same time A file lock helps programs keep track of whether or not a file is currently being accessed The program accessing the file sets a Lock on the file to let other programs know that they must wait Then when the program leaves the file it clears the lock making the file accessible to other programs It is important to stress that a file lock is not a security device Multiple programs can access the same file whether or not file locks are set on that file however by checking file locks a program can prevent a file from being damaged by refraining from accessing it while another program is using it It 3s not ne
242. rnal reasons by functions written in Pascal Assembly language functions return their result on the top of the R5 stack after all arguments have been removed Example File TEST2 PAS PROGRAM EXTERNAL FUNCTION Maximum x y INTEGER INTEGER BEGIN WRITELN Maximum 2 7 3 END File MAXIMU MAC START ADDI 6 R5 Throw away unused additional words MOV RS R2 Get 2nd argument MOV R50 R1 Get 1st argument CMP R1 R2 Ist gt 2nd BHI USET1ST Yes return 1st argument MOV R2 R5 No return 2nd argument RTN USETST MOV R1 CR5 Return fst argument RTN After producing MAXIMU PSB you would need to remember to refer to the file as MAXIMUM PSB to PLINK otherwise it would think the function being defined had the name Maximu instead of Maximum 15 2 1 Argument passing There are two methods of passing arguments in Pascal typified by Ta PROCEDURE x INTEGER and 2 PROCEDURE VAR x INTEGER in the first declaration x is referred to as a value parameter In the second declaration x is referred to as a reference parameter In general value parameters appear directly on the R5 stack while reference parameters denoting variables which can be modified appear as an address on the R5 stack which points to the parameter However there are exceptions arrays records and strings always have their address passed on the RS stack even when they appear as value parameters ASSEMBLY LANGUAGE SUBROUTIN
243. rogram Library code file for VALID PCF Enter the file specification of the Library you want to use In almost every case this will be the standard Library file STDLIB PCF The external Library contains routines used by your program and the compiler You must specify a Library except in the very rare case where you are Linking a root Library that is a library that has no library of its Own such as STDLIB itself For information on the external library see Chapter 16 Writing and Modifying an External Library File Now PLINK asks which files you want to link together OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 15 Please specify files to be linked into VALID One per Line ending in a blank Line amp File 1 Enter the specification of the first file then type a RETURN Now PLINK asks for another file File 2 x Remember that a single PCF file may be made up of several separately compiled modules If you are Linking only one file enter a RETURN here otherwise enter the file specification of the next module if you are Linking together more than one fite the file specifications do not have to be entered in any special order but at least one of these files must be a main program file rather than a module or you see the message Attempt to create new code file without main program block For information on module files see Section 6 1 Program Declarations Remember that you are entering AMO
244. rogram for a password but does not display the characters of the password as they are entered When your terminal is not in Charmode and you are using INPUT the monitor processes and filters your input For example it appends a Line feed to the end of a carriage return KEYBOARD and Charmode dive you a way to examine the input exactly as it is entered the monitor does no processing of the characters That means that for the example above to work after typing the password the user must type a carriage return AND a line feed KEYBOARD is a TEXT file For information on Charmode see Section TT22 1 Charmode INPUT OUTPUT and KEYBOARD are associated with the special AMOS file specifications TTY TTY and KBD See Section 10 2 1 for information on these special devices INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 5 If you are using READ to input data remember that you will have to do a READLN after end of line has been reached to make it read past the line feed at the end of the carriage return in order to reset EOLN to FALSE For example PROGRAM TestEOLN Count how many characters are in input VAR Source CHAR Input H Counter INTEGER BEGIN TestEOLN WRITE C Enter a line of characters READ Source Counter 0 WHILE NOT EOLN DO BEGIN WRITE Source Counter 1 READ Source END WRITELN WRITELNC number of characters Counter READLN Restore EOLN gt END Test
245. rolRecord FirstDataRecord Name Last 111 PreviousRecNum 0 WHILE RecNum lt gt O DO BEGIN SEEK EmpFile RecNum GETCEmpFile s IF SameNames Name EmpFile Mame THEN BEGIN Find TRUE EXIT Find END PreviousRecNum RecNum RecNum EmpFile NextDataRecord END Find FALSE END Find FUNCTION Remove Name NameRecord BOOLEAN Deletes specified record in EmpFile Returns false if not found VAR NextRecNum INTEGER BEGIN Remove TRUE IF Find Name THEN BEGIN NextRecNum EmpFile NextDataRecord EmpFile NextUnusedRecord ControlRecord FirstUnusedRecord ControlRecord FirstUnusedRecord RecNum PUT CEmpFiLe IF PreviousRecNum 0 THEN ControlRecord FirstDataRecord Name Lastt 113 NextRecNum ELSE BEGIN SEEKCEmpFite PreviousRecNum GET EmpFile EmpFile NextDataRecord NextRecNum PUT CEmpFileJ END SEEK EmpFile 0 EmpFile zControlRecord PUT CEmoFile END ELSE Name not found Remove false END Remove s Changed 30 April 1981 INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 33 FUNCTION NamePrecedesName Name1 Name2 NameRecord BOOLEAN Returns TRUE if Name lt Name2 BEGIN NamePrecedesName 13 IF Namel Last lt Name2 Last THEN TRUE ELSE IF Namel Last Name2 Last THEN IF Namel First lt Name2 First THEN TRUE ELSE IF Namel First Name2 First THEN NameT Middle lt Name2 Middie ELSE FALSE ELSE FALSE END NamePrecedesName FUNCTION Add
246. rsions of AlphaPascal and from the standard Pascal described by Jensen and Wirth in the Pascal User Manual and Report We have also included a section that provides hints on canverting Pascal programs written under earlier versions of AlphaPascal to the format used by the current AlphaPascal If you have never before programmed in Pascal you will probably want to skip this chapter and go directly to Part II Summary of AlphaPascal for information on the Alpha Micro Pascal or to the next chapter Operating Instructions and Characteristics for information on using the AlphaPascal compiler and Linker 5 1 PREVIOUS VERSIONS OF ALPHA PASCAL Previous versions of AlphaPascal were based on the UCSD Pascal programming system Version 1 4 In order to provide a Pascal that is more fully integrated with the Alpha Micro operating system and file system we now offer this new version of AlphaPascal that was expressly developed for the Alpha Micro computer To make Life easier for programmers who have written programs using previous versions of AiphaPascal we have tried to keep many of the same features and functions while adding a number of new extensions and abilities Most of the changes between this version and earlier versions are added features that do not require that you rewrite your earlier programs Several of the most important difference are The operating instructions for AlphaPascal have changed An important difference is t
247. s a menu of the responses you can enter Interrupt zHelp2 RET a Quit B Backtrace R Resume Interrupt Help OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 20 4 6 HELPFUL COMMAND FILES Although our discussions above on the compiler and Linker discussed several special uses of thos programs in general the information that you give to the programs will be fairly standard For example you will rarely want to use an external library other than STDLIB To make CMPILR and PLINK easier to use we have provided a number of special command files that you can use for most cases of compilation and Linking these files automatically supply much of the information needed by CMPILR and PLINK These command files are in the Command File Library Account DSKO 2 21 CA command file is a text file that contains a series of AMOS commands and input for those command programs Such a file allows you to execute a string of commands and provide a stream of input by simply entering the name of that file You will use these command files at AMOS command Level To invoke one of the files enter the name of the file followed by one or more file specifications For example suppose you want to use the command file named PC for Pascal compile to compile your program file SMALL PAS At AMOS command level enter PC SMALL The PC command file now invokes the Pascal compiler and tells it that you want to compile the file SMALL
248. s as the X Y row column coordinates specifying the screen position where you want the cursor positioned The top left hand corner of the screen is specified by the coordinates 1 1 For example the function CRT 12 35 positions the cursor at the 12th row and 35th column of the screen NOTE If you supply row and column coordinates that are out of range for your terminal unpredictable results could occur 11 2 2 2 Extended Screen Display Options If the first argument supplied to CRT is negative the CRT function assumes that you want to use the extended terminal handling options specified by the second argument For example the function CRT 1 00 tells CRT to select option 0 the clear screen option MISCELLANEOUS FUNCTIONS AND PROCEDURES Page 11 8 The screen handling options provided are Code Function Clear screen 1 Cursor home upper Left corner 2 Cursor return column O without Line feed 3 Cursor up one row 4 Cursor down one row 5 Cursor left one column 6 Cursor right one column 7 Lock keyboard 3 Unlock keyboard 9 Erase ta end of Line 10 Erase to end of screen 11 Protect field reduced intensity 12 Unprotect field normal intensity 13 Enable protected fields 14 Disable protected fields 15 Delete Line 16 Insert Line 17 Delete character 18 Insert character 19 Read cursor address 20 Read character at current cursor address 21 Start blinking field 22 End blinking field 23 Start line drawing mod
249. s nested block structure Many sample programs in this book contain several BEGIN END blocks See Section 6 2 Label Declarations for information on Labeling BEGIN END keyword pairs Labeling these keywords tells the compiler to report back to you with an error message 1f the BEGIN END keywords are not matched as your labels have indicated they should be 9 7 CONDITIONAL STATEMENTS Conditional statements allow you to execute certain sections of code oniy if specific conditions are satisfied This section discusses the IF THEN IF THEN ELSE CASE OF and CASE OF ELSE statements 9 7 1 IF THEN The IF THEN statement takes the form IF Boolean expression THEN statement where statement may of course consist of a compound statement A Boolean expression is one which evaluates to a Boolean value For example 125 is evaluated as FALSE since 1 is not greater than 5 For example If TestScore gt 90 THEN WRITELN Congratulations An At STATEMENTS Page 9 5 The statement s following the THEN clause are carried out if the Boolean expression evaluates to TRUE if it evaluates to FALSE control 15 transferred to the next statement after the IF THEN statement Note that the statement following the THEN keyword may itself be an TF THEN statement For example IF Single THEN IF Withalding gt 56 THEN Dependents 1 Which is the same as If Single AND Witholding gt 36 THEN If Single evaluates
250. s of x and y are incompatible You tried to use a modifying assignment operator on two pieces data that were of incompatible type For example you cannot use NUMBER DATA if NUMBER is an INTEGER but DATA is REAL since you cannot return an INTEGER result if you divide an INTEGER by a REAL number of String constant has wrong lenath for packed array Undefined labels occur in this function procedure Only s and lt gt are permitted with ARRAYS See Chapter 7 for information on ARRAY data types In x lt relation gt y x and y are incompatible Comparison of FILES is undefined In x IN y y must be a SET type In x IN y x must be compatible with base type of y Only s and are permitted with pointers Only z and lt gt are permitted with RECORDS lt t and 5 are undefined on SETs denoting end of source expected assumed missing CMPILR reached the end of the file but saw no period to end all program and module files with a period Remember Only INTEGER operands are permitted with sop Only INTEGER or set operands are permitted with Sop in x lt op y x and y are not both numeric in x op y x and y are not both sets Only numeric or set operands are permitted with op Only numeric INTEGER or REAL operands are permitted with op Preceding argument must not be a packed char field The preceding string constant has wrong Length The preceding SET variable has wrong size The pr
251. salary Let s assume that you want to enter 250 as your gross salary and 175 as your takehome Below is a sample run of your program AlphaPascal v2 0 What is your gross salary 250 RET What is your takehome salary 175 They keep 30 percent of your salary ALPHA PASCAL USER S MANUAL PART 1 THE ALPHA PASCAL SYSTEM The next two chapters introduce you to the AlphaPascal programming system Chapter 3 is aimed at the experienced Pascal programmer it discusses the differences between this implementation of Pascal and previous versions of AlphaPascal It also discusses the major differences between this Pascal and the standard Pascal as described in Jensen and Wirth s Pascal User Manual and Report The last section of Chapter 3 gives some hints for converting programs written in earlier versions of AlphaPascal over to the current AlphaPascal standards Chapter 4 gives full operating instructions for the various components of the AlphaPascal system the compiler the Linker and the run time package Chapter 4 tells you everything you need to know about the actual processes of creating compiling Linking and running an AlphaPascal program Chapter 4 also discusses file requirements and memory Limitations of the AlphaPascal system CHAPTER 3 COMPATIBILITY AND CONVERSION This chapter is aimed primarily at the experienced Pascal programmer who wants to know how this implementation of Pascal differs from previous ve
252. ses jt EXTERNAL FUNCTION XLOCK MD XLOCKMODE LOCK1 LOCK2 INTEGER INTEGER The type XLOCKMODE is defined as follows TYPE XLOCKMODE SETLOCK SETLOCKWAIT CLEARLOCK SYSTEMS FUNCTIONS AND PROCEDURES Page 14 7 These two declarations can be included in a program by using I XLOCKO The result of the XLOCK call will be returned in the integer variable RETCODE RETCODE XLOCK MODE LOCK1 LOCK2D Where MODE is one of the modes specified in XLOCKMODE and LOCK1 and LOCK2 are integers containing the Locks to be set If RETCODE is ever set to 1 this means that a bad mode was passed to XLOCK This can happen if there was an error in setting up XLOCKMODE 14 6 2 Setting a Lock A Lock is set using XLOCK mode SETLOCK For instance if the user had opened a file on channel 3 and was updating record 47 he might enter the following code into his Pascal file LOCK1 25 locking file 3 LOCK2 472 locking record 47 RETCODE XLOCK SETLOCK LOCK1 LOCK2 5 If the tock was successful then RETCODE is set to 0 If not the job number of the job that has that lock is returned in RETCODE 14 6 3 Setting a Lock and Waiting Until it is Available It is sometimes necessary to wait for a lock to become clear To do this mode SETLOCKWAIT is used instead of SETLOCK This mode assuming the above example is used as follows RETCODE XLOCK SETLOCKWAIT LOCK1 LOCK2 7 if the tock is held by another user the prog
253. sor and successor elements of the type For example PREDC B returns an You can also use the ORD function to determine the position of the character in the ASCII character set For more information on PRED SUCC and ORD see Chapter 11 Miscellaneous Functions and Pracedures DATA TYPES Page 7 5 NOTE Remember that CHAR data is only one ASCII character Another standard data type exists STRING which represents a collection of CHAR data For example A is CHAR data but ABCD is STRING data For information on STRING see Section 7 2 3 STRING 7 1 5 User Defined Scalar Pascal allows you to define your own scalar types To do so use the type declaration statement You will supply the name of the data type and the elements of which it is composed For examples TYPE Spectrum Violet Blue Green Yellow Orange Red Just Like any other scalar type your data type consists of ordered elements This ordering is reflected by the order in which you List the elements in the type declaration statement For example given the statement above Violet lt Blue Green and so on You can then declare and use a variable of the data type you have defined For example VAR Colors Spectrum IF Colors Red THEN WarmColor TRUE The relational operators have been defined for user defined scalar types and return a Boolean result Internally the computer stores each of these elements as an integer value F
254. ssion Note that all variables to which values are assigned must have been previously declared For example CardValue 9 56 assigns the value 9 56 to the variable CardValue The expression above must have been preceded in the program by a statement such as VAR CardValue REAL which declares that the variable CardValue may only assume real number values Most languages including standard Pascal only allow the value of a variable to be changed by an assignment statement Alphapascal allows the value of a variable to be changed within an expression For example 200 Sum Total 365 Pascal reads the expression above as 200 Sum Total 365 dX That is Pascal assigns the value 365 to the variable Total and then divides the value Sum by Total which is now 365 and adds 200 to it EXPRESSIONS Page 8 4 Remember that the assignment operator has the highest precedence and that Pascal evaluates expressions from left to right when operator precedence 1s equal The Assignment operator has extremely high Left precedence and very low right precedence That means that it binds itself strongly to the nearest element on the left but loosely to the remaining elements on the right To make this idea clearer consider the following expression Result 10 Score Cards 32 Pairs Singles The second assignment operator binds strongly to the variabile Cards but swallows up all of the expression to th
255. stant CONST Error You have entered an invalid number try again Now your statements can read WRITELNCError 3 6 4 TYPE DECLARATIONS The most important feature of Pascal is its use and definition of the concept of data types A data type is a set of data for example whole numbers that are alike in some way For more information on data types see Chapter 7 Data Types For now let s just say that Pascal gives you some very powerful ways of representing different kinds of data types Besides the standard types that Pascal recognizes for example the type INTEGER that represents whole numbers Pascal also allows you to define your own data types You must declare a user defined data type at the front Changed 30 April 1981 DECLARATIONS AND DEFINITIONS Page 6 5 of the main program or procedure in which you are going to access that data type The tvpe declaration takes this form TYPE identifierl type identifier2 type2 i identifierN typeN For example suppose you want to define a new data type that is a simple scalar type whose elements are MON TUES and WEDS You can do so by simply enumerating the elements of that type TYPE Days MON TUES WEDS On the other hand suppose you want to declare a more complicated data type such as a type of array TYPE NewArray ARRAY 1 10 OF INTEGER The declaration above declares an array named NewArray which contains 10 elements
256. t in CT D o 5 1 rt in E HE pas m bel on 5 pe D L4 i ky We can procedur just by Looking OpenFiles Readba program do the a The work m XIT a Q funct keyword PROGRAM or m Lows vou to exit or from a procedure ion to a one arque the Calin name of the j my a 4 Ss dd Sid RE naa PER ye ABO You na not supply EXIT with the program identifier use the PROGRAM keyword to i am where a has previously b The label may not iie out of the example ion statement at Cuff don black For STATEMENTS Page 9 3 5647 VAR Cost Percent Tip REAL Query CHAR LABEL 100 BEGIN Program Tip WBITELN C Let s calculate the waiter s tip WRITE Was it good service Y or N READLN Query IF Query N THEN GOTO 100 T WRITEC How much did you pay for dinner READLN Cost WRITE What percentage do you want to tip READLN Percent Percent 0 01 Tip 3 Percent Cost WRITELNC The tip is T1p 100 END Program Tip NOTE The AlphaPascal compiler is initially set so that it does not recognize GOTO statements that is it gives the error message Tllegal symbol if it encounters a GOTO statement in your program To tell the compiler that you want to use GOTO statements in a particular program the compiler option Gt must appear at the front of that program For information on the 6 compiler op
257. t also associates the specified file identifier with the specified AMOS file The invocation takes the form SETFILE Cfile identifier Dev Unit Filet File2 Ext Proj Prog INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 28 For example SETFILE NewFi le 0 0 F1 F2 RADSOC LST 0 0 The sample above is changing the extension of the AMOS file associated with NewFile to LST NOTE Specifying a zero for both the project AND the programmer number tells AMOS to use the current default project programmer number the account you are Logged into Specifying a zero for both the device AND the unit number forces AMOS to use the default device specification the device and unit you are logged into If you specify a device e g RADSOC DSK you can tell AMOS to use the default unit by specifying a negative 1 for the unit For a more lengthy example of the use of SETFILE see Section 10 2 8 GETFILE INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 29 10 3 SAMPLE PROGRAM TO DEMONSTRATE FILE HANDLING The program below is an example of a programming solution to a very common business problem the need for an efficient way of reading in organizing and maintaining employee information Our sample program below uses random file techniques to maintain the following information for a user defined number of employees name age and sex The employee records are maintained in alphabetical order by name of employee You may add delete c
258. t file is very efficient using the SEEK procedure you may randomly position to any record in that file without stepping through prior records In addition a random file is the only file which you may read from and write to without closing and opening it again Do not use READ and WRITE to get data from a random file use GETs and PUTs You should be aware that the order in which you do GET and PUT procedures makes a difference If you do a GET and then a PUT to update information in a random file the last record retrieved via a GET will be updated if you do a PUT and then do a GET you will get the record after the one you just updated A series of GETs will retrieve successive records in a random file just as it will a sequential file A series of PUTs will write to successive records The EOF function does not return TRUE after the end of a random file has been reached instead an error is generated This error will also be generated if you SEEK a record beyond the end of the file and then attempt a GET or PUT 10 2 1 2 Sequential Files Sequential file blocks are allocated in a Linked List on the surface of the disk with one word at the front of each block containing the disk address of the next block in the file Access to such a file is sequential since the system has to read each block in order to find out where a specific block is on the disk Sequential file blocks are 510 bytes The EOF function returns TRUE after the end of a
259. t some function or procedure or your program when any error occurs Of course you can only EXIT to leave a function or procedure which is currently active so you will probably want to have around some BOOLEAN variables to keep track of whether or not you are currently within routines which you might wish to EXIT from ERRORTRAP 3 Remember to set XEGERR back to zero before leaving ERRORTRAP otherwise your next error will abort to AMOS without calling ERRORTRAP 14 10 5 XERRORTRAP When STDERRORTRAP is called by entering a Control C it is possible to request a backtrace of suspended functions and procedures This backtrace begins with the caller of the caller of STDERRORTRAP which is usually the caller of ERRORTRAP and hence the routine which was suspended Thus should STDERRORTRAP be called by a function or procedure local to your ERRORTRAP procedure the backtrace will begin in the wrong place This can be corrected by using XERRORTRAP which takes a copy of the system INFOREC as its argument It is used as follows changed 30 April 1981 SYSTEMS FUNCTIONS AND PROCEDURES Page 14 16 PROCEDURE ERRORTRAP VAR INFOP INFOREC INFO INFOREC PROCEDURE P1 BEGIN XERRORTRAP INFOD END BEGIN INFOP ERRORINFO INFO 35 INFOP P1 INFOP XEGERR INFO XEQERR END Using XERRORTRAP the backtrace will be displayed beginning with the caller of the routine which invokes ERRORINFO thus producing a correct backtrace
260. ta between programs and the terminal Remember that your terminal is a TEXT file Two TEXT files have been pre declared for use with the terminal INPUT and OUTPUT If you omit the file identifier from the list of arguments given to READ and READLN the procedures assume that you want to use the file INPUT No file identifier in the List of arguments given to WRITE and WRITELN indicates that you want to use the file OUTPUT One last note on these procedures they convert REAL or INTEGER data to type CHAR For example when you says WRITE Result where Result is an INTEGER variable containing the number 12 WRITE displays the characters 12 on your terminal This is what you want to do when you send data to a terminal but be careful in using READS and WRITES on actual disk files Consider performing file operations on a large file of INTEGER data It would be very inefficient to handle that data in character form since every time you manipulated it vou would have to re convert it It would be far better to use GETs and PUTs rather than READS and WRITES to handle the numeric data since GETs and PUTs do no conversion 10 1 5 1 READ The READ procedure inputs a list of variables from the terminal or a file You should only use READ for TEXT files NOTE READ does not read an entire line of data up to a carriage return line feed Given the file variable Data the procedure READ Data Character performs these actions 1 Scans over and i
261. tegers 32000 0 1 450 MAXINT 36 Remember that the pre declared constant MAXINT is the largest integer that AlphaPascal can represent 32767 The standard identifier INTEGER designates the integer data type For example VAR Ellipse Counter Control INTEGER The operators that have been defined for integers are addition subtraction or sign inversion multiplication x integer division that is divide and truncate DIV modulus MOD the set membership operator IN and the relational operators Using other operators for example the real division operator on integers causes the compiler to generate an error message There are many functions that accept INTEGER arguments See Chapter 12 Mathematical Functions for a List of the trigonometric hyperbolic trigonometric and mathematical functions Two other functions often used on INTEGER data are the PRED and SUCC functions PRED returns the predecessor element of the data type SUCC returns the successor element of the data type For example given three variables ONE TWO THREE of type INTEGER and ONE 1 TWO 2 and THREE 3 PREDCTWO returns 1 SUCCC TWO returns 3 See Sections 11 1 6 and DATA TYPES Page 7 3 11 1 8 for information on PRED and SUCC 7 1 2 REAL Real numbers are decimal numbers that may contain a fractional part As noted in Section 5 6 Notation we can represent real numbers either in decimal notati
262. ter 1 TO 10 DO WRITELN Square root SGRT Counter2 END Main Program 3 Each time the statement after the DO keyword incremented by one The program above integers from 1 to 10 is executed Counter is prints the square roots of the STATEMENTS Page 9 10 A variant of the FOR DO loop exists that allows you to decrement the control variable It takes the form FOR Variable identifier s expression DOWNTO expression DO statement Each time the statement after the DO keyword is executed the control variable is decremented by one Note that it is possible that a FOR DO Loop may not be executed at all if the initial and terminal values of the control variable are not in the proper range For example the statement FOR I 5 TO 1 will not be executed but FOR I 5 DOWNTO 1 will be executed 9 9 WITH DO The WITH DO statement allows you to access fields of a record as if they were simple variables The WITH DO statement takes the form WITH Variable identifierl Variable identifierN DO statement The WITH DO statement simply gives you a shorthand way of accessing record fields without specifying the name of the record structure for each access See Section 7 2 7 RECORDS for information on records For example suppose you have a record made up of the following fields Carlnfo Model Carinfo Year Carinfo Color Carinfo SerialNumber You have 100 cars on your car lot and you want to know how many of them are
263. tes all lower case letters to upper case when considering identifiers In other words AlphaPascal considers the identifiers EvalQuote Evalquote EVALQUOTE and evalQUOTE to be the same identifier You may choose any combinations of letters and numbers for identifiers with the following exceptions Certain words called keywords or reserved words have been reserved by Pascal to identify statements and structures inherent to Pascal and may not be used as identifiers These keywords are Listed in the section below Other identifiers called standard identifiers have been pre declared by AlphaPascal This means that AlphaPascal recognizes these standard identifiers as denoting procedures functions and types already defined to AlphaPascal The difference between standard identifiers and keywords is that you MAY redefine standard identifiers so that they no longer represent predefined Pascal types functions and procedures In other words if you attach a new meaning to a standard identifier no error message is generated but the procedure function or type previously associated with that identifier is no longer available to the procedure or function in which you redefined the identifier Of course a re definition only applies to the program in which it appears For this reason you must be very careful when assigning identifiers not to inadvertently redefine a standard identifier whose procedure type or function you may have need
264. that are not underlined are called standard identifiers they are elements of the Pascal language which can be re defined by you The words that are upper and lower case and that are not underlined in the example above are variable names comments and string data supplied by the writer of the program The first Line of our sample program is called a comment It is ignored by the computer and has no effect on the execution of the program its purpose is to make the program easier to read for humans Comments in Pascal are denoted by enclosing text either with the symbols x and or with the symbols and Y 2 The second line declares the program name Salary The third line declares the variables Gross Takehome Deductions and Percentage and tells Pascal that they can only assume the values of real numbers For information on declaring programs and variables see Chapter 6 Declarations and Definitions The fourth Line contains a BEGIN statement this statement marks the beginning of a program block The end of this block and in this case the end of the program is marked by the END statement on line 13 Within this block we send questions to the terminal display sixth and eighth Lines and read data from the terminal keyboard seventh and ninth lines On the tenth and eleventh Lines we compute the answer we need based on the data we received from the user of the program The twelfth Line sends the
265. the array using variables for the subscripts For example PROGRAM SquareIt VAR Square ARRAYUT1 10J OF INTEGER Counter INTEGER BEGIN Squarelt 3 Counter 5 1 WRITELN lt Squares of the integers 1 to 10 are FOR Counter 3 1 TO 10 DO BEGIN OS ScuareLCounter Counter Counter WRITELN SquarelCounterd ENDE END T Squarelt The small program above creates array Square of ten elements The FOR DO loop increments the variable Counter from 1 to 10 accesses the array Location indexed by Counter and writes the square of Counter into that Location of the array For example location Square 5 contains the number 5 5 or 25 You can use a similar type of loop to retrieve data from an array NOTE Sometimes you can fill an array without using loops For example InvoiceNumL A 5 InvoiceNum 8 1 accomplishes the same thing as FOR I 55 1 TO 5 DO InvoiceNumL A I s InvoiceNum B 11 DATA TYPES Page 7 10 7 2 2 1 Multi dimensional Arrays Until now our discussion has been of one dimensional arrays that is arrays with just one index Pascal also allows you to constr ct arrays with an unlimited number of dimensions You might consider a multi dimensional array as an array of an array To declare such a structure include additional subscripts in the declaration Suppose you want to keep track of a five element array each element of which is in turn a five element array TYPE InvoiceNums ARRAYL A
266. though the use of PLINK may at first look complicated once you begin to use it you will find that its questions are rather self explanatory The paragraphs below discuss the different ways in which you can use PLINK The last few paragraphs of this section Sections 4 4 4 and 4 4 5 discuss the PLINK options To use PLINK at AMOS commmand level enter PRUN PLINK Now PLINK asks Code file Enter the specification you want given to your final PEF file This specification may be that of an existing file or it may designate a new file It may be the same as or different than the specification of one of the files you are going to Link Make sure that you supply a valid AMOS file specification that contains a filename of no more than six characters for example DSK4 VALIDC110 4D For the purposes of our discussions Let s say that you enter VALID Code file VALID PLINK will automatically assign the file a PCF extension If you do not include a device and account specification PLINK assumes that you want to Link a file that is in the device and account you are logged into At this point PLINK asks you different questions depending on whether or not the specified PCF file already exists In the next sections we will step through the three situations which can occur 1 you are creating a new file 2 you are replacing an existing PCF file 3 you are updating a single module in the PCF file For now let s assume that PLINK has ask
267. tion see Section 4 5 2 1 The GOTO Options G and G 2 9 5 NULL STATEMENT One of the features that make Pascal programs especially flexible is the fact that you may include a null statement within your programs A null statement allows you to include extra semicolons within compound statements and to omit statements in certain program constructs For example consider the CASE expression beiow CASE expression OF 1 statement statement 2 5 NuLl statement 3 Tia A E gt Statement ELSE statement4 By including just a semicolon after value 3 we tell the CASE expression to perform no statement if the expression evaluates to 3 STATEMENTS Page 9 4 As another example IF C D THEN Flag i TRUE ELSE Nutl statement after ELSE gt ELSE NewFlag True IF A B THEN 1 The use of the null statement above allows us to attach the second ELSE to the first IF THEN construct Otherwise the second else would be performed when C lt gt D rather than when A lt gt 8 9 6 COMPOUND STATEMENT The body of a Pascal program is a compound statement that is it is marked with the BEGIN and END keywords and contains one or more statements between those keywords even if the enclosed statement s is a null statement see the paragraph above Section 9 5 The Null Statement Each individual statement may also consist of a compound statement The use of compound statements is what gives a Pascal program it
268. tions Short BOOLEAN FORWARD The forward reference gt FUNCTION AskAnswer Query CHAR BOOLEAN BEGIN 4 AskAnswer AskAnswer FALSE IF Query Y OR Query y THEN AskAnswer 1 3 TRUE ELSE IF Query 12 THEN Printinstructions Short END AskAnswer 7 PROCEDURE Printinstructions BEGIN PrintInstructions Short FALSE 4 Initialized to long instructions 5 WRITE Do you want short Instructions Y or N READLN Query IF AskAnswer Query THEN Short TRUE Display Short END Printinstructions 3 BEGIN Main Program WRITELN We re going to compute your tax return J WRITELN WRITELNC At any time in this program you may review the instructions WRITELN by answering any Y or N question with a WRITEC Do you want instructions Y or N 2 READLN Query IF AskAnswer Query THEN PrintInstructions Short WRITEC Do you want to average Y or N READLN Query IF AskAnswer Query THEN WRITELN OK We Ll average 7 T Now compute taxes END Main Program Jj DECLARATIONS AND DEFINITIONS Page 6 11 Note that when the procedure block PrintInstructions appeared after the Function AskAnswer we did not include the formal parameters for that procedure since the procedure heading appeared at the time of the forward reference 6 6 4 Formal Parameters We would Like to include a word here on formal parameters Parameters are variables
269. to the error message the operator or identifier that is the source of the error For example in the list below the error message above appears as CBOPNBN in x op y x and y are not both numeric In our example above CMPILR substituted into the error message the operator C op2 causing the problem and displayed the message 8O0PNBN In xty x and y are not both numeric The symbols in the error messages that are replaced by elements from your program when the message is displayed are lt op gt Operator XXX user defined Identifier XXX YYY keyword zzz Changed 30 April 1981 ALPHA PASCAL COMPILER ERROR MESSAGES C 1 THE CANEANXI LANENOT CASGASTI CASGFILJ LASGMAT CASGSWLI CBOYULBI CBEXARLJ CSEXCMT CREXFRLI CBEXINSJ CBEXINTJ CBEXPRLJ CBEXRRL 1 CBEXSRLI BLKDOT I LBOPINT CB0OP105 80PNBNJ CBOPNBS CBOPNOS CBOPNUMJ CCALAPBI CCALARLI LCALARSI CALART ECALARVI ECALCHRA Changed Page C 3 ERROR MESSAGES kek Undefined error You shouid never see this error message Please report it and the circumstances under which vou saw it to Alpha Micro in x AND y x must be of type BOOLEAN In NOT x x must be of type BOOLEAN See Chapter 8 for information on BOOLEAN operators In x sy the types of x and y are incompatible It is illegal to assign files to one another See Chapter 7 for information on the FILE data type in x lt ap gt y the type
270. u try to Link a file make sure that it has already been compiled that is that the POT POZ and POB files exist PL assumes that you want to link a single file and that you want to use the standard external library STDLIB 4 6 3 Compiling and Linking a Single File PCL DO To use the PCL file enter PCL followed by the name of the file You want to compile and Link For example PCL TRSRCH The compiler compiles the file TRSRCH PAS into the files TRSRCH POT TRSRCH PO2 and TRSRCH PO3 Next PLINK Links these intermediate files into TRSRCH PCF The command file assumes that you want to Link a single program file and that you want to use the standard external Library STDLIB 4 6 4 Updating a Single Program Module PU DO To use the PU file enter PU followed by the name of the module you want to update followed by the name of the PCF file you want to link the module into For example PU MODULT TRSRCH PLINK now Links the module into TRSRCH PCF This file assumes that MODULT has already been compiled and that you want to use whatever external Library TRSRCH was originally linked under OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 22 4 6 5 Compiling and Updating a Single Program Module PCU DO To use the PCU file enter Peu followed by the name of the module you want to compile and update followed by the name of the PCF file you want to Link the module into For example PCU MODULT TRSRCH CMPILR now
271. u unmount a disk you prevent BASIC and most system programs from being able to access that device Note that VOLID is included even though it is not needed because a volume id is not returned when a disk is unmounted VOLID is required at all times 14 7 3 Error Codes The error or return codes specified above have the following meanings 1 amp 7 5 1 MOUNTED The device was successfully mounted and the volume ID is in VOLID or whatever the second string was called 14 7 5 2 UNMOUNTED The device was successfully unmounted VOLID is unchanged 14 7 5 5 DEVNOTFOUND The specified device was not defined at system generation and is not in the system device table VOLID is unchanged 14 7 3 4 BADHASH The device was mounted but it was a storage module device with a BADBLK SYS When the new BADBLK SYS was read it was found to contain a bad hash total VOLID is unchanged 14 7 3 5 NOVOLID The disk was successfully mounted but there was no volume ID on the disk Nate that MOUNTED and NOVOLID specify successful mounting of the disk UNMOUNT specifies a successful UNMOUNT DEVNOTEOUND and BADHASH indicate errors occurred while attempting to mount the disk If either of these errors occur you should not try to access that device SYSTEMS FUNCTIONS AND PROCEDURES Page 14 11 14 8 TIME The TIME procedure places the contents of the system clock into the two specified variables The system clock contents increment ev
272. umber of bytes and MOVERIGHT Source array Destination array Number of bytes where Destination must be a variable Given the same arrays and same subscripts the results of MOVERIGHT and MOVELEFT will Look exactly the same For example if Source is the packed array of CHAR 1234567890 and Destination is the packed array of CHAR Gk ek ke a T o MOVELEFT Sourcel6J bestination 6 5 MOVERIGHT SourceL6 Destinationt61 5 will produce the same packed array 67890 The MOVELEFT procedure above moves the characters in this order 6 7 8 9 and O The MOVERIGHT procedure above moves the characters in this order 0 9 8 7 and 6 The onty time this will become important is when you are moving characters within the same array For example PROGRAM TestMove VAR Source PACKED ARRAY 1 23 OF CHAR BEGIN TestMove Source i Days are never too long MOVELEFT CSourcel6 Sourcel11 10 WRITELN Source Source 3 Days are never too long MOVERIGHT Sourcel6 Sourcel11 10 WRITELN Source END TestMove 3 The program above prints are never ever too Long STRING AND CHARACTER ARRAY FUNCTIONS AND PROCEDURES Page 13 9 and ever ever ever too long MOVERIGHT and MOVELEFT can produce radically different results depending on the data you give them You must be careful to choose the correct MOVE function for your particular application 13 2 5 SCAN The SCAN function returns the number
273. ur project Library account x 0 The account you are logged into For PSB files this pattern is System memory User memory partition The account you are logged into Your project Library account x 0 The Pascal Library Account PAS DSKO L7 5 For example if you are logged into DSK1 100 3 and want to execute the program PRIME PCF you enter PRUN PRIME OPERATING INSTRUCTIONS AND CHARACTERISTICS Page 4 4 PRUN assumes a file extension of PCF Pascal first Looks for the file PRIME PCF in the account you are logged into in this case DSK1 1100 37D next it looks in your project Library account DSK1 0100 07 Finally it Looks in the Pascal Library Account DSKO C7 57 If it doesn t find the file in any of these places you see the error message Cannot OPEN PRIME PCF file not found Of course if you give a complete file specification including device and or account specification Pascal will Look for the file on the device and account you have specified without going through its search pattern The standard complete AMOS file specification consists of a device specification a file name a file extension and an account specification For example PRUN HWK1 PRIME PCF 200 56 4 1 5 Program Restrictions AlphaPascal handles your programs via a virtual memory paging system This means that there is no limit to the size of your programs NOTE Oniy programs are paged not data allocated by NEW However
274. used within a function or procedure Pascal greatly extends the usefulness of your routines by allowing your program to supply those values at the time that you invoke your function or procedure This means that you can use your routines in a wide variety of situations on a wide range of data Parameters give your functions and procedures a way to communicate with the program that calis them The variables that are specified at the time you define your function or procedure are called the formal parameters The values you supply with the actual invocation of your routine are called the actual parameters For example given the function heading FUNCTION Salary Takehome Gross REAL REAL the formal parameters are the variables Takehome and Gross When we invoke that function we might do so using constants Raise zSalary 183 2500 Or we might use variables which contain those values Raisez Salary Net Total Note that the variable identifiers we use as formal parameters do not have to be the same as the identifiers for the actual parameters You can think of the formal parameters as placeholders for the actual data which will be used The actual parameters are plugged into the formal parameters in the same order as they appear in the routine Invocation For instance in the example above Net takes the piace of Takehome and Total takes the piace af Gross The total number of actual parameters must match the number of forma
275. ut data in file gt FOR I 1 TO 5 DO BEGIN Loop WRITE Enter Year READLN Year Report Year PUT Report WRITE C Enter Profit READLN Profit Report sProfit PUT Report END Loop 7 RESET Report Open file again for input WRITELNC Year 6 Profit 18 amp Print header gt WRITELN mmm m m ne me a a sme ae me e ae a aee mme e mes a oe ae e a a e a gt WRITELN BEGIN 4 While loop 7 Year Report GET Report Profit s Report GET Report WRITELN Year 6 Profit 20 2 Format output gt END While loop 3 END FormatOutput WHILE NOT EOF Report DO Print contents until End of file b The program above prints a neat table of the form Year Profit 1971 650000 56 1973 1205600 34 1975 1865030 89 1977 100450677 34 1979 82380000 90 INPUT OUTPUT FUNCTIONS AND PROCEDURES Page 10 13 o 10 1 6 PAGE The Page procedure writes a form feed to the specified file The invocation takes this form PAGECfile identifier where file identifier is a file variable 10 1 7 RESET The RESET procedure rewinds your file to the beginning In effect it performs a CLOSE and then OPENs the file for input The invocation takes the form RESET file identifier where filecidentifier is a file variable that is associated with the file you want to reset As does OPEN RESET inputs the first file component into the buffer variabile for you qu 10
276. w we ll simply show you one way to use them to compile and link a new program made up of only one file For this demonstration we will use one of the command files provided with your system PCL DO This command file contains a series of commands and data that automatically invoke CMPILR and PLINK for you and provide necessary information to those programs NOTE Remember that the larger your memory partition is the faster your programs will compile At AMOS command Level enter PCL followed by the name of your program Leaving off the PAS extension Then type a RETURN For example PCL SALARY RET Now the PCL command file runs CMPILR and PLINK for you As your program is compiled you see a display something Like this PRUN CMPILR AlphaPascal V2 0 Source file name SALARY Diagnostic file name lt return gt for terminal AlphaPascal Compiler Version 2 0 lt Q PROGRAM lt Am mmm 12 Lines 10 47 seconds 68 79 Lines minute No compilation errors If CMPILR spots an error while it is compiling your program for exemple if we Left the semicolon off the end of the second Line CMPILR pauses and tells vou about the problem For example VAR Gross Takehome Deductions Percentage REAL Line 2 CINISOP or expected inserting Hit RETURN to continue The message above tells us that a semicolon is missing in front of the symbol VAR C LINISOP identifies the portion of the compiler that caught
277. whose declaration has not yet appeared in the program There are times when for aesthetic or practical reasons or because the two routines call each other you must invoke a procedure or function before its definition appears in the declaration part of the program Pascal provides a way to do this The forward declaration tells the Pascal compiler We ll define this later don t worry that you haven t seen its declaration yet The forward declaration takes the same form as the heading of a procedure or function declaration except that the word FORWARD replaces the procedure or function block In effect we separate the heading from the block For example take a look at the procedure DrawLine PROCEDURE DrawLine Character CHAR LineSize Angle REAL FORWARD DECLARATIONS AND DEFINITIONS Page 6 10 Now a function or procedure declaration may appear that invokes the procedure or function Later within the declaration part of the program the actual procedure or definition block appears oreceded by the name of the function For example PROGRAM TaxReturn This program computes tax returns First it asks if the user wants instructions short or long VAR Short BOOLEAN Query i CHAR PROCEDURE Display Short BOOLEAN BEGIN T display gt TUT This is the procedure that actually displays the instructions It prints a long or a short file depending on the value of Short gt END Display 3 PROCEDURE PrintInstruc
278. words remaining in the user partition This number can be used to estimate how many items can be allocated by NEW before memory capacity is exceeded You can use SIZEOF to determine how many bytes any particular obfect will require 14 4 MAINPROG MAINPROG is a boolean function that returns no arguments It returns TRUE if the PCF file is being used as a program or FALSE if it is being used as a Library MAINPROG can be used for debugging purposes It can be used to write a program which can also be used as the library of a checkout program that makes sure that the functions and procedures defined in the original program now a library to the checkout program are implemented correctly To do this the program would have the form PROGRAM declarations BEGIN 2s dnitialization TF MAINPROG THEN BEGIN statements END END 7 SYSTEMS FUNCTIONS AND PROCEDURES Page 14 3 The statements are only executed if the program is being used as a program and not as a Library The checkout program testing the functions and procedures in the above program would then declare them as EXTERNAL functions and procedures in order to call them with test arguments E 14 5 SPOOL SPOOL is an assembly Language routine that vou can call from Pascal to spool a disk file to the Line printer s To spool a file is to insert it into the printer queue after which you can continue to do other things while your file waits in t
279. y 8 pair of F or Ce 32 symbols For example READ PLaneRoute This variable is accessed by FLIGHT procedure A comment may appear between any two symbols in a program cover more than Changed 30 April 1981 GENERAL INFORMATION Page 5 5 one line and may appear in the middle of a statement Comments may not be nested but gt symbols may appear within the symbols and vice versa this allows you to comment out areas of programs that contain comments For example C WRITELN RecCount t Report 4 of records sorted READLN lF Error THEN ErrorFix Error condition lg 3 4 LEGAL IDENTIFIERS Identifiers are groups of characters that denote variables types constants procedures functions programs record fields and record tagfields As one example of an identifier consider a variable that assumes the values of a range of school test Scores it might appear in a program as the identifier Scores Identifiers in AlphaPascal may consist of combinations of upper and Lower case letters and numbers but must begin with a letter Identifiers may be as many characters as you wish but only the first eight characters are used by Pascal in recognizing the identifier That means that the identifiers STANDARDBUFFER and STANDARDBUFFOON Will be recognized by Pascal as the same identifier STANDARD IMPORTANT NOTE AlphaPascal folds Lower case identifiers to upper case This means that it transla
280. y Language Subroutines O What actually happens is this when you specify a PSB file to PLINK PLINK then inserts a reference to that file in your final PCF file When you execute the PCF file AlphaPascal searches for the specified PSB file using the standard file search pattern we discussed at the front af this chapter and then Loads that file into memory from the disk Cif the file is not already in system or user memory next it executes the routine when called by the program When PRUN finishes executing the PSB file it deletes it from memory You can force PRUN to leave the PSB file in memory by explicitly loading the file into memory via the monitor LOAD command before using PRUN to run the program that calls the PSB file If the PSB file has been placed into memory via the LOAD command the file remains in memory until you use the DEL command to remove it If you want the contents of the PSB file to be physically part of your PCF file so that this search and load procedure does not take place you may specify the LINK option after the name of the PSB file when you link that file in For example File 1 MODUL1 File 2 MAINPR File 3 XPUT PSB LINK i H oH The LINK option refers only to the single file specification on the same Line as the option request If you are going to physically link a PSB file into your PCF file the PSB file cannot be Larger than one disk block OPERATING INSTRUCTIONS AND CHARACT
281. y of your routines on disk Second the Linking process is faster if you only need to specify a Library rather than several files contain your modules Finally if it becomes necessary to modify a routine you need only change it in the Library to update all your programs which use it Another possible use of Libraries is to generate multiple configurations of a program A single program could be Linked to a variety of libraries each of which define the same set of functions and procedures but each of which do so with different definitions This might be used to configure a generalized set of applications programs for use in different specific applications l It is not necessary to specify EXTERNAL declarations for most of the functions and procedures in STDLIB This is NOT a feature of libraries Rather the compiler has been written to automatically include EXTERNAL declarations for these commonly used routines There is really very Little difference between a program file and a library file Both are actually AlphaPascal programs The only difference is that if Program A uses Program B as a library then Program B is executed with the purpose of initializing the library d t8 global variables in the Library before Program A is executed It 15 possible for a library to itself have a Library Thus Program A can use Program B as a library and Program 8 can use Program as a library in which case C then 8 and finally A are executed

AMOS AlphaPascal

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