PART II: BASIC REFERENCE GUIDE - PolyMorphic
Contents
1. 3 76EH02 means 43 76 10702 or 3 76 x 108 or 376 3 76E 02 means 3 76 x 106702 or 3 76 x x 106 or 376 01 or 0 0376 91 or 90 0376 3 76E 62 means 43 76 16 02 oc 3 76 3 76E 02 means 3 76 16 G2 or 3 76 x MK 2 4 2 STRINGS A string constant is represented as a sequence of Characters between double quotation marks string Blanks and ASCII TAB may be included ASCII CR may not 2 5 VARIABLES Variables may be either numeric or string Any variable Reference Manual PolyMorpnic Systems BASIC Cbd Page 9 may be an array of unlimited dimensions except function variables or function parameters Numeric variable names consist of one or two characters a single upper case letter optionally followed by a single digit String variable names are identical to numeric but are followed by a dollar sign 2 6 ARRAYS Botn numeric and string array names are the same as numeric and string scalars except for a subscript list immediately following the name A scalar is a non arrav or a one dimensional array of one element This has the form of a list of expressions separated by commas and surrounded by parenthesis A 1 3 or Z8 I43 In a MAT statement an array does not reguire a subscript list A given upper case letter or upper case letter and digit may be used in the name of a numeric scalar numeric array numeric function string scalar string array and string function all in the same program Each2. Tvpe error on READ That s not a BASIC data file MAT subscript error I can t do that to a protected file Too many digits for hardware Renumbering error The minimum allowable precision is 6 The maximum allowable precision is 26 ses LOAD interrupted I can t do that to an OUT file
3. see followed bv a comma gt LIST number To displav a single line tvpe its number without a comma gt LIST number REN Re numbers all program lines numbering them lb 20 etc To re number all program lines starting with a number other than 10 type REN and the desired first line number gt REN 150 To use an increment other than 10 type REN and a first line number then the desired increment gt REN 5 5 Ri REN automaticallv changes all references co line numbers within the program to correctly reflect the new line numbers Programs using the special variable LINE described in paragraph 2 7 should not be renumbered RUN begins execution of a program from the first line and does a CLEAR Page 16 PolyMorphic Systems BASIC C ad Reference Manual To begin execution at some other line type RUN and the line number The existing run time environment is preserved no CLEAR is done CTRL X interrupts the running of a BASIC program hold down CTRL key and nit Y key CONTINUE resumes execution of a BASIC program after an interruption Use CON after the gt gt prompt only SCR oOrSCRATCH scratches erases everything in user memory and closes all open files DEL Geletes blocks of lines Give the first and last line numbers of the block to be deleted DEL number number I only one number is given only that line will be deleted XREF cross references program variables with the numbers of
4. 1 REM Test for Division bv Zero Error 10616 IF ERR 1036 THEN 10199 10020 RESET ERR GOTO 9209 1w104 PRINT DIVISION 3Y ZERO IN LINE LINE 10200 RETURN The decimal values returned by the ERR special variable after an error occurs during execution of a BASIC program are listed below Page 45 PolyMorphic Systems BASIC Co Reference Manual 1624 1025 1026 1627 1628 1029 1030 1031 1032 1033 1634 1035 1036 1637 1636 1639 1040 1041 1042 1043 1044 1645 1046 1647 1055 1051 1052 1053 1054 1055 1056 1857 1058 1059 1663 1061 1062 1063 1664 10955 1072 1073 1074 1075 1088 1279 Svntax error Svntax error Subscript error Bad argument error Dimension error Function definition error Out of bounds error Type error Format error I can t find that line FOR NEXT error RETURN without GOSUB Division by zero Function definition error Missing matching NEXT READ error Qops BASIC goofed Cops BASIC goofed Input error Out of memory I can t do that directly Argument mismatch error Length error Overflow error Can t continue That s not a BASIC file Nothing to save That channel not open That channel not open for INPUT That channel not open for OUTPUT End of file on that channel That program is for a different version of BASIC CHAIN programs must be saved with SAVEF That record is past the end of the file I can only do that to a disk file End of file on that channel
5. DATA Jan Feb Mar READ statements read the data in the DATA statements starting at the first data statement in the program or the data statement at the RESTOREG line number READ statements contain lists of numeric or string variables to be read corresponding to the data in DATA statements Every time a variable in a READ statement causes a data item in 2 DATA Statement to be read a pointer is advanced to the next READ variable and to the next DATA statement item Data Reference Manual PolyMorphic Systems BASIC CHG Page 19 items in excess of READ variables go unread READ numeric variables must correspond to DATA numeric Gata and READ string variables to DATA string data RESTORE sets the data pointer to the first iata item in the first DATA statement in the program A line number may be given RESTORE linenumber The next data item read will be the first data item in line n or after line n if line n contains no DATA statement If no number is given the data pointer is set to the first data item in the first DATA statement in tho program INP n is a function which tests for characters in the input buffer and accepts input of characters from the keyboard INP 0 returns if there is nothing in the input buffer INP 1 returns the integer value corresponding to the ASCII code of the next character waiting in the input buffer NOTE See Section 11 of this reference for INPUTTING FROM DISK FILES 5 3 OUTP
6. terminating the record The READ and WRITE statements allow more than one string variable to be stored in a single record There is no necessity to pad strings to fill out the record Nor does the programmer have to read a record as a string the size of the record and then by programming break the record into its logical data elements 10 3 DATA FILE MODES OF OPERATION There are three modes of operation of BASIC data files l OUT files 2 INPUT files 3 INOUT files our files are created by a BASIC program Only one CUT file mey be open on a Disk Drive at one time OUT files may not bc reca from INPUT files provide data which may be read sequentially by a BASIC program INPUT files may not be written to INOUT files are files which may be read from or written to by a BASIC program Records may be directly accessed read and rewritten in place INQUT files may not have new records appended to them It is necessary to create the file as an OUT file with space for the maximum number of records expected to be required for the file 10 4 FILE STATEMENTS Reference Manual PolyMorphic Systems BASIC Cuu Page 39 FILE is a statement which operates on a channel number specified as an expression separated from FILE by a colon with en effect determined by the function keyword which follows the channel number separated by a comma FILE n keyword Example 1wd PILE 6 OPEN lt 2 gt Real estate INPUT Followi
7. the lines in which they appear WALK allows vou to single step through a program The program RUNS but each statement executed is displayed on the screen and each statement waits for a single character command to be typed by the operator An X will execute one statement A D will execute one statement and DUMP the scalar variables A G will continue full speed RUN in WALK mode CYRL Y is disabled DUMP will cause the current values of all scalar variables and array dimensions to be printed on the screen Reference Manual PolyMorphic Systems BASIC Cdu Page 17 Section 5 PROGRAM STATEMENTS 5 1 GENERAL STATEMENTS REM is for comments BASIC ignores tne statement REM and all characters to its right on the same line REM lines in a SAVE file without line numbers will not be loaded STOP stops execution To resume type CON ASSIGNMENT STATEMENTS LET may precede assignment statements but need not be used The usual form of an assignment statement is variable expression Values mav be numeric ot string l Asl 110 AS Total To assign several variables the same value at once use a multiple assignment 109 A Bs Order of assignment is rignt to left Both numeric and string variables cannot be on the left side of a multiple assignment statement CLEAR erases all variables and reclaims their memory space DIGITS sets the precision of numeric calculations BASIC defaults to eignt digits of pre
8. use will designate a different variable in each context The first element of an array is given an index of 1 unless a DIMU statement precedes the DIM then the first element of an array is number 0 2 7 SPECIAL VARIABLES Tne following variables are recognized anywhere a normal BASIC variable would be recognized except that their values may not be changed by the programmer Pl Always has the value 3 1415926535897932384626432 It ds truncated at the right two digits at a time when current precision is less than 26 ERR The value is the error code of the last error that occurred LINE Page li PolyMorpnic Systems BASIC C i Reference Manual Returns the number of the line in which the last error occurred Reference Manual PolyMorphic Systems BASIC CQO Page 11 i This special variable is set to the index number of an element by certain array functions See MAT It may be changed in an assignment statement Page 12 PolvMorphic Systems BASIC CUd Reference Manual Reference Manual PolyMorphic Systems BASIC COJ Page 13 Section 3 INPUTTING A PROGRAM To add or change a line type a line number and the new line An old line having that number will be deleted automatically To delete an existing line without replacing it type the line number and hit RETURN To delete two or more lines in sequence use DEL described below BASIC will accept a maximum of 80 characters per line Blanks count as characters
9. Blanks are never required in the interpretation of a statement except of course inside string constants Removal of blanks reduces tne amount of memory space a program requires Program lines must begin with a line number from 0 through 65535 Blanks or tabs BEFORE line numbers are ignored Multiple statements mav be included on one line bv using one line number and separating statements with a back slash A GOSUB or function call in the midst of a multiple statement line will return to the proper statement even though it is not the first statement in the line An IF statement will not execute ANY of the remaining statements on a line if the condition is false and there is no ELSE clause If there is an ELSE clause the statement works as one might expect a true condition will only execute the statement before the ELSE clause and a false condition will only execute the part of the statement between the ELSE clause and the next N Multiple IF statements may be used on one line Page 14 PolyMorphic Systems BASIC Cod Reference Manual Reference Manual PolyMorphic Systems BASIC C0 Page 15 Section 4 COMMANDS LIST displavs a BASIC program on the screen To displav a portion of a program tvpe the first and last line numbers of the block of lines vou wish to see without spaces gt LIST number number To displav the program from a particular line to the end of tne program tvpe the number of the first line vou wish to
10. MP Outputs scalar numeric program variables to the output device in human readable cabular form WAIT halts program execution prints Waiting on the screen and awaits any keystrike before resuming execution PAUSE n stops execution for n ticks one tick is 1 68 second n must be between b and 65535 inclusive Expressions for n are evaluated ON ERROR linenumber or ON ERROR THEN statement provides a routine or statement to be executed whenever there is an error Any error that occurs after an ON ERROR statement has been executed causes the ON ERROR statement to be executed ON ERROR THEN linenumber does an implied GUSUB to the line number when the routine at the linenumber executes a RETURN program execution will resume after the point of error Without tne line number THEN is ignored and statement is executed ON CAPE linenumber Upon typing CTRL Y BASIC begins execution of the statement number following ON ESCAPE Otherwise identical to ON ERROR NOTE indiscriminate use of ON ESCAPE can result in programs which are impossible to abort except by pressing the Load button RESET Page 24 Polymorphic Systems BASIC CG Reference Manual inactivates all previously executed and active ON ERROR or ON ESCAPE statements Subsequent errors are handled exactly the same as if no GN ERROR or ON ESCAPE had been executed H Reference Manual PolyMorphic Systems BASIC Cd Page 25 Section 6 FUNCTIONS AND SUB
11. PART II BASIC REFERENCE GUIDE Reference Manual PolyMNorphic Systems BASIC C99 Page 1l REFERENCE MANUAL This brief description of PolyMorphic Systems BASIC is intended to provide an easy to use daily reference for the BASIC programmer The commands etc described here are discussed at length in the manual System 88 Disk BASIC A Manual IN ALL CASES SEE THE BASIC MANUAL FOR DETAILS See also the System 88 User s Manual This reference applies to PolyMorphic Systems Disk BASIC version Ci and COWL Previous versions were tape 8V27 9V27 AUD POO Pul disk AG1 BU8 BGBA BOSC Page 2 PolyMorphic Systems BASIC cod Reference Manual Reference Manual PolyMorphic Systems BASIC COG Page 3 Section 1 ENTERING BASIC LOADING RUNNING AND SAVING LEAVING BASIC 1 1 ENTERING BASIC When BASIC is part of the System Disk it is always instantly available To use BASIC start the system then when you see the Exec prompt type BASIC You will then see the BASIC version number and the BASIC prompt gt This BASIC prompt indicates that you are communicating with BASIC i e that the BASIC interpreter is loaded and awaiting your keyboard input 1 2 LOADING AND RUNNING PROGRAMS You can run a BASIC program from the Exec prompt or without typing BASIC Just type the file specifier the file name preceded py the drive number if necesary the system will note the BS suffix and automatically bring in BASIC T
12. ROUTINES 6 1 INTRINSIC FUNCTIONS 6 1 1 Standard Intrinsic Functions Functions are called thus function name argument list The argument list is separated by commas SQRI returns the square root of the argument EXP returns the value of e 2 71828 raised to the power specified by the argument LOG returns tne natural logarithm base e of the argument LOGT returns the logarithm to the base 16 of the argument cos returns the cosine of the argument presumed to be in radians Si z returns the sine of the argument TAN returns the tangent of the argument ABS returns the absolute value of the argument NT returns the nearest integer less than the argument Page 26 PolyMorphic Systems BASIC C0 Reference Manual G u z returns 1 if the argument is negative if it is zero and l if it is negative RND returns a real random number greater than J and less than l The argument gives the seed value which must be greater than and less than l RND n If the seed is an integer number greater than zero RND returns an integer number from l through the number given RND 1 always returns 1 Using the same seed in the same program always produces the same sequence of pseudo random numbers RANDOMIZE is a statement not a function which sets the random number generator seed according to the current value of the low order 16 bits of the real time clock This insures that each run of a progr
13. UTTING FROM THE BASIC PROGRAM PRINT printlist outputs text corresponding to the values of a list of numeric and string expressions following PRINT The expressions are separated by commas Numeric values are converted to decimal and princed String literals are denoted by double quote marks Quotation marks are of course not printed PRINT followed by nothing produces a blank line If there is a comma after the last element in the list no Carriage return will be printed after the last element Otherwise a carriage return ASCII CR is output Page 29 PolyMorphic Systems BASIC Cd Reference Manual The default PRINT format is left justified with the cursor displayed all numeric elements are separated by blanks and a carriage return automatically generated after a line is output This default format may be altered by the programmer with TABs and format strings TAB moves the cursor i e the next output character position to the print position specified 160 PRINT TAB 20 A will cause the value of A to be printed at position 20 on the screen Format Stings The printed format of numbers can be altered by using format strings in PRINT statements A format string begins with a per cent sign followed by another character or characters indicating how the format is to be changed These other characters are c puts commas into numbers as required e g 1 000 395 puts a dollar sign immediatelv pre
14. am will produce a new randomly selected pseudo random sequence TIME returns the 16 low order bits of the real time clock TIME 0 returns the 16 bits TINE with a non zero argument returns the 16 bits and sets the timer to J COSH teturns the hvperbolic cosine of the argument SINH returns the hyperbolic sine of the argument returns the hyperbolic tangent of the argument ATAN returns the arctangent of the argument from PI 2 to PI 2 radians ASIN returns the arcsine of the argument from PI 2 to P1 2 radians Q Reference Manual PolyMorpnic Systems BASIC C00 Page 27 FREE 0 prints the number of unused bytes available for a user s BASIC program in RAM memory MEM variablename returns the address in decimal in memory of the stated variable Argument may not be an expression 6 1 2 Intrinsic Functions Directly Accessing Memory and the Processor Numbers used in these functions must be integers POKE memorv address expression is a statement not a function which stores the value of the expression in the 8980 address given by memorv ad ress NOTE POKE is very dangerous Careless use of POKE may derange the operating system the BASIC interpreter the BASIC program and many types of I O devices in utterly unpredictable ways PEEK memorv addrees returns the contents of the specified B93 address 6 1 3 Intrinsic String Functions LEN string variable returns the number of cha
15. another program EDIT etc until BASIC has been left via BYE You may also use Exec RESET to throw away the ability to CONTINUE and reclaim the 68089 stack space Page o PolyMorphic Systems BASIC C29 Reference Manual Reference Manual PolyMorphic Systems BASIC C03 Page 7 Section 2 OPERATORS AND OPERANDS 2 1 Mathematical Operators The following operators are recognized Unary minus Exponentiation Multiplication Division Addition Subtraction wx 2 1 1 Priority of Mathematical Operations Unary minus is done first then exponentiation then multiplication and division then addition and subtraction Unary minus is allowed before any variable or parenthetical expression Multiple unary minuses are considered equivalent to a single unary minus Chains of operations of equal precedence Ex A B C D E 2 are done left to right Parentheses are allowed and may be nested to any depth 2 2 Relational Operators Symbol Operation Equals lt Is less than gt Is greater than lt gt Does not equal gt or gt Is greater than or equals lt or lt Is less than or equals BASIC will evaluate relational operations and return al if true or 6 if false Strings or numerics may be compared but not arrays String comparisons do alphabetic comparison using the collating sequence of ASCII This means lower case letters are greater than upper case 2 3 Logical Operators AND OR NOT Logical operators ha
16. ceding numbers Z eliminates trailing zeroes If a format string contains a pound sign as the character immediately following the sign the format as defined in that format string will thereafter be the default format Tne null format string returns the default format to the standard default format when used as illustrated 200 PRINT b Format strings must be seperated from elements of the print list with commas BASIC includes some standard formats for numeric data other than the detault format The characters below are used in combination with the character to use these other standard formats In all cases below digits in excess of m are rounded If there are digits in the element to be formatted in excess of n asterisks are printed in the field No error is generated by the asterisk substitution 4 Reference Manual PolyMorphic Systems BASIC C Page 21 E Right justified in a field n characters wide with m digits to the right of tne decimal point nFm Integers only right justified in a field n characters wide ni E Right justified in a field n characters wide in scientific notation regardless of length with m digits to the right of the decimal point nEm NOTE See Sections 12 and 13 for GUTPUTTING TO DISK AND OR TO PRINTEER INP port returns an 8 bit value which is the result of doing an 8989 INP instruction from the specified port The port number may be from to 256 OUT port exp
17. ch item within the 5x5 array A is a string consisting of a maximum of 15 characters 7 3 WATRIX OPERATIONS Given one dimensional arrays A B and C of equal size the statement 100 MAT A BtC sets A 1 equal to B 1 4C 1 A 2 equal to B 2 C 2 etc Although A above must be an array B C can be expressions to be evaluated etc 100 MAT ASSQRI B 24C72 sets A 1 equal to the square root of B 1 2 cC 1 72 A 2 equal to the square root of B 2 2 C 2 72 etc MAT can be combined with these other statements LET PRINT READ INPUT PLOT IF THEN ELSE For instance the instruction 109 MAT IF A 0 THEN STCP results in a stop if ANY item in array A is 9 109 MAT PRINT A prints out all the elements in the array A in order Note the comma at the end of the line above This will cause the printing of each element sequentially across the screen Without the comma each element will be printed on a seperate line on the screen Reference Manual PolyMorpnic Systems BASIC Ci i Page 33 In general MAT takes tne size of the first array it finds to the right of MAT as the number of repetitions to make In IF statements fewer than this number of repetitions may be made because a true condition will stop the MAT sratement s repetition A multi dimensional arrav is considered uni dimensional with the elements taken in row major order Thus the effective dimension of any array is the product of all the sizes of its dime
18. cision but will operate at from six to twenty six digits To change precision type DIGITS n North Star Hardware math boards will be automatically discovered by BASIC if plugged in and will restrict DIGITS to from 8 to 14 Page 16 PolyMorphic Systems BASIC COJ Reference Manual 5 2 INPUTTING DATA 5 2 1 PROM KEYBOARD INPUT prompts for Gata input from the keyboard INPUT is followed by a numeric or string variable which is set egual to tne data entered from the keyboard l If immediately followed by a variable INPUT displays a question mark as a prompt INPUT can be immediately followed by a prompt string e g li INPUT Enter date X in wnich case no question mark appears More than one variable may follow INPUT and each will be prompted for in succession The first prompt is a question mark or the prompt string given Further prompts are question marks One string value may be input per line keyed in Many numeric values may be input per line by separating them by commas blanks or ASCII TABs IWNPUTI is the same as INPUT except that it does not print a carriage return when the operator keys RETURN thus the display cursor remains after the data he next INPUT will thus appear on the same line as the INPUTI 5 2 2 Inputting Data from the BASIC Program DATA statements contain data used by the program A comma separated list of numeric or string constants must follow each DATA statement 109 DATA 10 29 39 455 118
19. e number CN variable or expression GOSUB line number anv kind of assignment statement or another IF statement If the IF condition is not met expression evaluates to false execution passes to the next line except see ELSE below ELSE When the condition in an IF THEN statement is not met execution can continue with another statement preceded by ELSE ELSE must be the next statement after THEN and must be on the same line ELSE can introduce another IF THEN If ELSE is to be followed by GOTO the GOTO statement is assumed and need not appear only the line number nced be included EXIT linenumber branches execution out of a FOR NEXT loop EXIT terminates ALL active FOR NEXT loops reclaims the associated stack memory and passes execution to the line whose number follows EXIT EXIT leaves ALL current loops CHAIN string expression brings in tne next program and runs it automatically as in CHAIN Program name or CHAIN A The CHAINed to program must have been saved in token SAVEF or encrypted SAVEP format If the CHAINed to program is on a drive other than tne Reference Manual PolyHorphic Systems BASIC C80 Page 23 System Drive i e the default drive give the drive mumber or lt gt or lt gt if defined The run time environment is preserved no CLEAR is implied LINK string expression operates in the same manner as CHAIN except that user memory is CLEARED and SCRATCHed DU
20. ernal buffer to be written to the disk READ n readlist inputs data from a file READ n operates identically to READ but obtains data from file n rather than from data statements The variables are separated by Carriage returns ASCII CR in each record Example 100 READ 4 A A B C PRINT n printlist writes data records to the file from the printlist Records oniy not elements from the printlist are Gelimited witn CRs The format of the record may be controlled identically to the manner the format of a PRINT to the screen is controlled Example l PRINT 4 51 A 8F2 B B Reference Manual PolyMorphic Systems BASIC C d Page 41 INPUT c readlist Reads data into the variables specified in the readlist Example 109 INPUT 4 A B BS CAUTION Files written using WRITE should be read using READ and files written using PRINT should be read using INPUT INP n transfers one bvte from the data file when used in the following manner 1igd A INP c Page 42 PolvMorpnic Systems BASIC C4d Reference Manual Reference Manual PolyMorphic Systems BASIC C Page 43 Section 11 USING A PRINTER FROM BASIC A BASIC program can use the facilities provided by the Universal Printer Driver of System 33 First the printer must be assigned a channel number Thus 106 FILE 2 LIST attaches channel 2 to the printer Thereafter PRINT statements of the form 106 PRINT n printlist will cause the contents of the
21. le 100 DEF FNA1 A4 B A B For multi line functions the format is DEF FNvariable name argument list followed by lines defining the function The last line in the function definition must be FNEND Example 109 DEF FNA X 119 vour statement 120 your statement 139 FNEND Reference Manual PolyMorphic Systems BASIC Cd Page 29 Notice the DEF cannot have any additional statements on the same line Arguments in function definitions are dummies or formal parameters and are replaced by the actual arguments given in eacn function call If variables with the same names as the names of the arguments in the argument list exist elsewhere in the program their values are not changed the formal parameters are local to the function definition Tne number of arguments in the function definition must egual the number of arguments in the function call 6 3 SUBROUTINES Execution of a subroutine begins with GOSUB line number from oucside a subroutine and ends with RETURN in the subroutine RETURN returns execution to the statement following the most recent GOSUB they may be nested Tne number of GOSUBS must equal the number of RETURNS Page 39 PolyNorphic Systems BASIC C ad Reference Manual Reference Manual PolyMorphic Systems BASIC COJ Page 31 Section 7 STRINGS ARRAYS AND MATRIXES 7 1 ARRAYS Elements within arrays are specified by a subscript to the array variable giving the position of the ele
22. ma SAVEF filename Saves the program in internal or token format The program will load faster when saved in this format However it cannot be edited using the System 88 Editor nor listed using PRINT or TYPE SAVEP filename Like SAVEF above but saves the program in encrypted form Once a program in SAVEP format has been loaded into BASIC BASIC will only execute the commands RUN SCR or BYE Thus SAVEP is intended as a simple means for application developers to protect the logic of BASIC programs Only programs saved with SAVEF or SAVEP can be CHAINed or LINKed to Programs saved with SAVEF and SAVEP always auto execute when loaded 1 4 LEAVING BASIC To leave BASIC type EXEC or BYE You will be returned to the operating system EXEC leaves the BASIC interpreter in memory the BASIC program loaded the current state of all variables intact all data files open and allows you to continue running your BASIC program by typing CONTINUE in Exec and then CONTINUE again in BASIC BYE does the same thing as a SCRATCH which erases program and variables and closes data files Always use BYE when finished with a program that involves data files if the Program does not close then itself Reference Manual PolyMorpnic Systems BASIC COX Page 5 NOTE EXEC requires a certain amount of 8080 Stack space and should not be used casually Always finish work in Exec after EXEC and get back to BASIC with CONTINUE Don t run
23. ment within the array For instance the nth item of the array xX is cited thus X n An array may have more than one dimension An element is then referenced by its position in each dimension in the order that the dimensions were given in the DIM statement e g 5 10 DIM dimensions the array thus DIM arrav variable number of elements Example 100 DIM X 500 Multi dimensional arrays are dimensioned DIM X n m Example 100 DIM x 5 160 Arrays must be dimensioned before any element can be referenced An array can be re dimensioned in a program after a CLEAR statement has been executed NOTE CLEAR resets ALL variables to zero or null and destroys the run time environment DING Tne first element in an array the array base is number 1 by default To number elements starting with 0 use DIN before using DIM This is particularly useful when converting programs written in another version of BASIC where the array base defaults to J DIMI te establisnes 1 as the array base Page 32 PolyMorphic Systems BASIC C00 Reference Manual 7 2 STRINGS and STRING ARRAYS Scalar strings are automatically created and dimensioned to a maximum length of 10 characters when first used in a program However strings may be dimensioned to any size 169 DIM A 1 18 dimensions a scalar string of 160 characters Strings arrays may be created with unlimited number of dimensions 160 DIM A 5 5 15 indicates that ea
24. ng are the allowable keywords OPEN opens a data file Example 10 FILE 4 OPEN filename mode filename is any string expression evaluating to a valid System 83 file name CLOSE closes a channel Example 169 FILE 4 CLOSE Wo filename or mode is required The channel may be the LIST channei a data file or a user defined channel POS position sets the read and write pointers to a particular data record POS is preceded by a channel number and followed by a record number expression which evaluates to an integer from 1 to 65535 Records are automatically numbered starting with 1 in the order written originally to the file Example lwd FILE 4 POS A would position tne read pointer to the relative record number as expressed by the value in che variable A Page 44 PolvMorphic Svstems BASIC C Z Reference Manual REW rewind positions to record l Example 109 FILE 4 REW 10 5 FILE INPUT OUTPUT STATEMENTS WRITE n printlist 4 writes data to a file Each element in the printlist is delimited by a carriage return when it is written for compatability with READ n Example 169 FILE 4 P0S N 110 WRITE 4 A A B C The WRITE statement MUST be immediately preceded by a POS statement as illustrated above NOTE It is good programming practice to immediately follow the WRITE or PRINT described below statements wita a REWind statement This forces the data which may have been written only to the int
25. nis does not happen if you have tagged the file with some suffix other than the BS suffix tagged to BASIC files by defauit To load a disk file while in BASIC type LOAD and the file specifier If the file name uses some suffix other than BS you must give the suffix From Exec you can load BASIC and run a program with a Single statement filename The filename must have a suffix of BS You can interrupt the running of a BASIC program from the keyboard by typing CTRL X hold down the CTRL key and type y pr Lys An interruption in the running of a BASIC program will cause the system to stop and display a line number and a double BASIC prompt gt gt This double prompt tells you that a BASIC program has been interrupted while executing the line with the number displayed It also indicates that you are communicating with BASIC To load POLY 68 tape BASIC programs see FILMS in the User s Manual 1 3 SAVING PROGRAMS SAVE SAVEF SAVEP Programs are saved into disk files by using the SAVE SAVEF or SAVEP commands plus a comma or semi colon Page 4 PolyMorphic Systems BASIC C Reference Manual Sample format SAVE lt 2 gt Program Name SAVE filename or SAVE filename Saves the program in text form so that it can be edited using the system editor and printed using PRINT and TYPE Program files created with SAVE do not auto execute when loaded unless the SAVE command is followed with a semi colon instead of a com
26. nsions If any effective dimension of an array in a MAT statement is less than tne effective dimension of the first element a dimension error results Ctherwise only the required part of each array is used During the execution of a MAT statement the special variable is incremented from 1 through the effective dimension of the first array Thus 108 MAT A sets the array A to the identity sequence 1 2 3 4 5 6 Also is set to tne index of the array element which caused termination a MAT IF statement MAT IF A 1 THEN PRINT will print the index of the first element of the array A which is equal to l 7 4 SPECIAL ARRAY FUNCTIONS All the functions below take the following form function name arrav variable as illustrated 106 A SUM B NOTE arrays created with DIM2 in effect have zeroetn elements which may not be evident to the Programmer but which nonetheless are included in the computation of these functions SUM returns the sum of all the elements in an arrav PROD returns the product of all the elements in an array MIN and MAX recurn the largest or smallest element in an array is set to the numoer of that element Page 34 Polvilorphic Systems BASIC Cg Reference Manual nean 2 returns the mean of the elements in an array STD returns the standard deviation of the elements in an array Reference Manual PolyMorphic Systems BASIC C0d Page 35 Section 9 DEBUGGING FEATURES RUN line number
27. outputting to disk files to a printer or special devices A channel number may be given as an expression evaluating to a number Id 7 In tne following discussions to a channel number a t m 0 16 2 DATA FILE FORMATS There are two formats of BASIC data files l Fixed record lengta 2 Variable record length When a data file is created by writing the records of it to a channel opened in the OUT mode BASIC keeps track of the length of each record If all lengths are exactly egual when the file is closed it is given a fixed record length which is one greater than the measured length The increment is for a carriage return at the end of every record Fixed length record files are directly accessed in about Ke of a second for long files faster for extremely short iles Variable length record files may be directly accessed but it is not generally recommenced as it may be extremely time consuming When the records of a file are re written using INCUL mode modes are described below 6 shorter record may be written in place of any record but not a longer one A shorter record is padded with zero bytes between the last data character and the terminating ASCII CR which is not moved Page 38 PolyMorpnic Systems BASIC C99 Reference Manual If READ and WRITE described below are used in creating and maintaining the file the records will have a CR between every data element or field in the record plus a CR
28. printlist to be printed on the printer which has been initialized by System 383 To attach special devices see the printer discussion in the BASIC manual Page 44 PolyMorphic Systems BASIC C00 Reference Manual Reference Manual PolyMorphic Systems BASIC C09 Page 45 Section 12 ERROR HANDLING If BASIC detects an error in a program or command it will normally stop execution of the program and display a message briefly describing the error This is quite useful for amp programmer testing and debugging a program However it may be disastrous to a non programmer who is executing an application program to have a program abort with an error message and a BASIC prompt BASIC C ij incorporates several statements and functions to aid programmers in developing bomb proof application programs Each of these has been previously described Reviewing they are ON ERROR statement ON ERROR THEN statement LINE special variable ERR function RESET statement ine following program illustrates the use of ON ERROR THEN processing to trap errors an execute error correction ptoce ures in an application program REM REM Illustration of the use of RESET in REM restoring normal error processing REM and the implicit GOSUB in ON ERROR REM Also illustrates the LINE function REM 9000 ON ERROR THEN GOTO 10099 RETURN 9910 X RND 10 1 9920 PRINT 1 x 9030 X RND 10 1 040 PRINT 1 X 9459 GOTO 9016 10900 E E
29. racters of the string currently stored in the specified string variable VAL string variable returns a numeric value given by regarding the string argument as a number in scientific notation or integer form STRS expression returns the scientific notation or integer representation of the value of the expression VAL SUR expr does nothing STRS may include the 3 format declarators of the PRINT statement before the numeric argument Page 28 PolvMorphic Systems BASIC C90 Reference Manual ASC string variable returns an integer corresponding to the ASCII code for the first character of the string specified CHR expression returns a one character string which is the ASCII character corresponding to the value of the integer argument LEFTS string variable n returns the left most n characters of the string n may be an expression If n lt 0 a null string is returned if n gt LEN string variable the entire string is returned RIGHTS string variable n like the above but returns the rignt most n characters MID string variable n m returns tne nth through the mth characters of the specified string 1f n m one character is returned I n gt LEN string variable or m lt l or n gt m the null string is returned 6 2 USER DEFINED FUNCTIONS Use FN to define your own functions Functions may be one line or multi line The format for one line functions is DEF FNvariable name argument list function Examp
30. ression is a statement not a function which outputs the expression to the specified port System 85 uses 8653 ports d through 32 The rest are free for user I O devices 5 4 LOOPS FOR and NEXT FOR and NEXT provide for program loops FOR NEXT loops may be nested Also see EXIT 5 5 BRANCHING STATEMENTS Goro continues execution at a specified program line GOTO n where n is the line number of the next line to be executed ON expr GOTO line linex liner moves the program counter to one of several specified program lines The evaluated variable or expression following ON indicates which of the line numbers following GOTO is to be selected i selects the first number following GOTG 2 the second and so forth Page 22 PolyMorphic Systems BASIC C Reference Manual ON expr GOSUB line line t line moves the program counter to the line whose number follows GOSUB which is assumed to be the first line of a Subroutine after execution of the subroutine execution returns to the line immediately following the ON GOSUB statement Otherwise this statement resembles GN GOTO IF expr THEN statement conditionally executes a statement following THEN in the same line IF is followed by an expression which evaluates to true l or false b or NOT 1 THEN can be followed by a GOTO statement or just the line number to GOTG SOTO is implied GOSUB line number RETURN PRINT print list ON variable cor expression GOTO lin
31. runs tne program starting with the line indicated DUMP prints a list of and the current value of all tne scalar numeric variables currentlv making up the run time environment XREF prints a listing of variables with the numbers of the lines in which they occur Command only NOTE Both DUMP and XREF may have their output routed to the printer if one is attached as described in Section 11 WALK lets you run the program one line at 2 time After beginning to WALK to run the next line type X To execute a single statement and DUMP type D To RUN from the current line type G WALK may be followed bv a line number ON ERROR and ON ESCAPE See ON ERROR and ON ESCAPE statements ERR is set to the error code of the most recent error For instance ON ERROR PRINT ERR displays the error code ot each error wnen it occurs then continues after the OW ERROR statement LINE returns tne line number of the line in waich the most recent error occurred Page 36 PolyNorphic Systems BASIC COG Reference Manual RESET clears previous ON ERROR and OW ESCAPE statements ends WALK Reference Manual PolyMorphic Systems BASIC C Page 37 Section 19 DATA FILES 10 1 FILE CHANNELS BASIC provides eight file channels numbered d through 7 G for inputting data from the keyboard 1 for outputting to the screen 25 3 for outputting to a printer or special device Channels 4 5 6 and 7 may be used for inputting from or
32. ve this order of execution NOT Logical complement bitwise arithmetic operations As above relational operations As above AND Logical conjunction bitwise OR Logical disjunction bitwise Page 3 PolyMorphic Systems BASIC COS Reference Manual The logical Operations are done separately on the corresponding bits in the 16 bit integer representation of their arguments bitwise This should mean that 169 IF NOT 1 THEN X will not do X However the IF statement recognizes NOT 1 as false so X is in fact executed NOT expression where expression yields 1 is equivalent to NOT 1 2 4 ARITHMETIC PRECISION BASIC rounds numbers to a precision of 8 decimal digits This precision may modified to any precision from 6 to 26 decimal igits by the use of a DIGITS statement Once a DIGITS statement is executed the precision will remain as specified until another DIGITS statement is executed or until BASIC is re loaded The DIGITS statement takes the following form 109 DIGITS 12 When DIGITS is used all variables are CLEARed Therefore the DIGITS statement should normally be the first statement in a program BASIC will automatically discover a North Star floating point board if one has been installed When the floating point board is present in the system BASIC can only compute 6 to 14 digits of precision 2 4 1 NUMERIC REPRESENTATION Whole numbers longer than the current precision are represented in scientific notation thus
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