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Action manual - Noni Kimbel and Jim Patchell

1. Address Description 00 C9 OS and ACTION Variables CA CD Free Space CE D3 ACTION Variables D4 FF Atari Floating Point Registers 100 3FF Operating System 400 4FF ACTION Variables 500 5FF Atari Floating Point Buffer 600 MEMLO 1 Operating System MEMLO ACTION compiler STACKS MEMLO 200 ACTION Editor Line Buffer MEMLO 300 ACTION Hash Tables MEMLO 750 ACTION Editor Text Buffer ACTION Compiler Code Space TOP 800 ACTION Compiler Symbol Table MEMTOP screen Memory A000 ACTION Cartridge CO000 FFFF O S ROMS etc NOTE the Compiler Code Space starts wherever the Editor Text Buffer ends This makes both the Editor Buffer and the Compiler Buffer dynamic in memory For more information on this see part V chapter 2 Appendix C Error Code Explanation In this appendix we ll describe the meaning of each of the error numbers you could encounter while programming in ACTION Included are those errors which the ACTION system itself discovers but not those which the operating system discovers errors 128 255 Error Code Explanation 0 Out of system memory See Part Il section 4 3 and Part V section 4 4 to find out how to remedy this error 1 Missing double quote in a string 2 Nested DEFINES You can not nest the DEFINE directive 3 Global variable symbol table full 4 Local variable symbol table full
2. b2 LSH 5 3 is the same as b2 b2 LSH 5 3 This shorthand form can save you a lot of typing over the long method and even generates better machine code in some instances 5 2 Structured Statements If only simple statements were available you d be severely limited in the number of things you could do on a computer The only way you could repeat a group of statements a number of times would be to type them out in the same order the right number of times If you wanted to repeat a group of ten statements ten times you would end up typing in 100 statements You would not be able to execute a group of statements conditionally that Ib only execute them if some specified test is satisfied The purpose of structured statements is to solve these and other problems Structured statements as a whole are divided into two separate categories Conditional Statements and Looping Statements We will discuss each of these categories separately 5 2 1 Conditional Execution Conditional execution allows you to test an expression and execute various statements depending on the outcome of the test Since the expression controls conditional execution it is called a conditional expression Three ACTION statements allow conditional execution IF WHILE UNTIL WHILE and UNTIL are looping statements and will be dealt with later but we ll discuss IF immediately after the rules governing conditional expressions 5 2 1 1 Conditional Expr
3. Execution continues here after EXIT PrintE End of Table RETURN Output 2 1 times 2 equals End of Table As you can see in the output the statement PrintCE j is never executed The EXIT statement forces execution to hop to the statement PrintE End of Table EXIT isn t very useful when utilized alone but if you use it in conjunction with an IF statement i e make the EXIT into a conditional jump out of the loop it can be very useful as the program on the following page shows Example 3 PROC timestwo CARD i 0 j DO start of DO OD loop IF i 15 THEN EXIT Exit in an IF condition FI l 1 add 1 to i J i 2 set j equal to i 2 PrinteC i Print times 2 equals EXIT Here s the EXIT statement PrintCE j OD end of DO OD loop eeee Execution continues here after EXIT PrintE End of Table RETURN Output 3 1 times 2 equals 2 2 times 2 equals 4 3 times 2 equals 6 4 times 2 equals 8 5 times 2 equals 10 6 times 2 equals 12 7 times 2 equals 14 6 times 2 equals 16 9 times 2 equals 18 10 times 2 equals 20 11 times 2 equals 22 12 times 2 equals 24 13 times 2 equals 26 14 times 2 equals 28 15 times 2 equals 30 End of Table This usage turns an infinite loop block into a finite one EXIT can control the execution of a loop but is not considered a structured loop controlling statement because it doesn t stand on its own that is it is only useful when u
4. is false because the AND is seen as a bit wise operator being used in an arithmetic expression whereas F000 AND 0F00 is true because the AND join two simple relational expressions and so is a special operator as used in complex relational expressions Chapter 5 Statements A computer program would be useless if it could not actively operate on data You would be allowed to declare variables constants etc but there would be no way to manipulate them Statements are the active part of any computer language and ACTION is no exception Statements translate an action you want to do into a form which the computer can understand and execute properly This is why statements are sometimes referred to as executable commands There are two classes of statements in ACTION simple statements and structured statements Simple statements contain no other statements within themselves whereas structured statements are collections of other statements either simple or structured put together following a certain order Structured statements may be broken down into two categories 1 Conditional Statements 2 Looping Statements Each category is discussed separately in the section on structured statements 5 1 Simple Statements Simple statements are those which do one thing only They are the basic building blocks of a program since any action the computer performs is a simple statement of one kind or other There are two simple st
5. BYTE x 8000 y 0 declare x as BYTE placing it at memory location 8000 declare and initialize y to zero CARD ctr 83D4 declares and initializes bignum 0 three variables as CARD cat 30000 type In the last two examples you may note that the variables need not be on the same line The ACTION compiler will keep reading in variables of the type given as long as there are commas separating them so remember not to put a comma after the last variable in a list strange things will happen if you do Variable declarations must come immediately after a MODULE statement see section 7 4 or at the beginning of a procedure or function see sections 6 1 I and 6 2 1 If you use them anywhere else you will get an error 3 4 2 Numeric Constants Numeric constants are not explicitly declared Their usage declares their type A numeric constant is considered to be of type BYTE if it is less than 256 otherwise it is considered to be of type CARD For all practical purposes negative constants e g 7 are treated as type INT Constant Type 543 CARD 0D BYTE f42 CARD W BYTE Chapter 4 Expressions Expressions are constructions which obtain values from variables constants and conditions using a specific set of Operators For example 4 3 is an expression that equals 7 as long as we take the operator to mean addition If the operator were instead multiplication would result and
6. Powerful Flexible Fast Precision Software Tools tok m A Division of ICD A Division of ICD Incorporated A reference manual for The ACTION System A complete programming environment designed for your Atari home computer system The programs cartridges ROMs and manuals comprising the ACTION system are Copyright c 1983 2012 by Clinton Parker This book is Copyright c 1983 2012 by Clinton Parker This manual was written in August 1983 All rights reserved Reproduction or translation of any part of this work beyond that permitted by sections 107 and 108 of the United States Copyright Act without the permission of the copyright owner is unlawful This version of the manual was done with the permission of the copyright owner Clinton Parker It was edited by James Patchell in June 2012 All efforts were made by the editor to make certain that this is an accurate version of the original however it was made by doing an OCR on the original manual and then editing the resulting text in Microsoft Word Itis possible that many of the errors that were created by the OCR process were missed On the other hand managed to correct some of the errors that were in the original manual It took me several months to complete this task but it was done mostly to preserve what consider to be one of the most impressive programs that came out in the early days of computing ACTION was without any d
7. lt fund type gt FUNC lt identifier gt lt addr gt lt param decl gt lt addr gt lt comp const gt Routine calls lt routine call gt lt FUNC call gt lt PROC call gt lt FUNC call gt lt identifier gt lt params gt lt PROC call gt lt identifier gt lt params gt Parameters lt param decl gt lt var decl gt NOTE maximum of 8 paramters allowed A 7 Statements lt stmt list gt lt stmt gt lt stmt list gt lt stmt gt lt stmt gt lt simp stmt gt lt struct stmt gt lt code block gt lt simp stmt gt assign stmt gt lt EXIT stmt gt lt routine call gt lt struct stmt gt lt IF stmt gt lt DO loop gt lt WHILE loop gt lt FOR loop gt Assignment Statements lt assign stmt gt lt mem contents gt lt arith expr gt lt mem contents gt lt arith expr gt lt mem contents gt lt arith expr gt lt mem contents gt lt arith expr gt lt mem contents gt lt arith expr gt lt mem contents gt amp lt arith expr gt lt mem contents gt lt arith expr gt lt mem contents gt lt arith expr gt lt lt mem contents gt LSH lt arith expr gt lt mem contents gt RSH lt arith expr gt lt mem contents gt MOD lt arith expr gt EXIT Statement lt EXIT stmt gt EXIT IF Statement
8. If this method doesn t work we can only suggest that you insert diagnostic Print statements into your program e g PrintE In loop FOR x 1 to 100 PrintBE x might be used to debug a FOR loop which has run amuck Part IV The ACTION Language Chapter Chapter Chapter Chapter Chapter 1 Introduction 2 ACTION Vocabulary 2 1 Special Notations 3 Fundamental Data Types 3 1 Variables 3 2 Constants 3 3 Fundamental Data Types 3 3 1 BYTE 3 3 2 CARDinal 3 3 3 INTeger 3 4 Declarations 3 4 1 Variable Declaration 3 4 2 Numeric Constants 4 Expressions 4 1 Operators 4 1 1 Arithmetic Operators 4 1 2 Bit wise operators 4 1 3 Relational Operators 4 1 4 Operator Precedence 4 2 Arithmetic Expressions 4 3 Simple Relational Expressions 4 4 Complex Relational Expressions 5 Statements 5 1 Simple Statements 5 1 1 Assignment Statement 5 2 Structured Statements 5 2 1 Conditional Execution 5 2 1 1 Conditional Expressions Chapter Chapter Chapter 5 2 1 2 IF Statement 5 2 2 Null Statement 5 2 3 Loops 5 2 3 1 DO and OD 5 2 3 2 EXIT Statement 5 2 4 Loop Controls 5 2 4 1 FOR Statement 5 2 4 2 WHILE Statement 5 2 4 3 UNTIL Statement 5 2 5 Nesting Structured Statements 6 Procedures and Functions 6 1 PROCedures 6 1 1 PROC Declaration 6 1 2 RETURN 6 1 3 Calling Procedures 6 2 FUNCtions 6 2 1 FUNC Declaration 6 2 2 RETURN 6 2 3 Calling Functions 6 3 Scope of Variables 6 4 Parameters 6 5
9. This procedure puts the leadin to the game on the screen CARD ctr PrintE Welcome to the guessing game I m PrintE thinking of a number from 0 to 100 PrintE All you have to do is type in your PrintE guess when ask you to PutE PrintE l ll keep track of how many games PrintE you ve played and tell you how PrintE many times you ve guessed the number PrintE in fewer tries than your goal but PrintE first yoo have to give me your goal PutE Print Type your goal here gt goal InputC FOR ctr 0 to 2500 a delay loop to give the DO senge of real time to the OD player Put 7D clear the screen RETURN end of PROC Intro PROC tally This procedure prints out the current tally Print Vou have played PrintC numgames PrintE games Print and in PrintC beatgoal PrintE of those you PrintE have beaten your goal of PrintC goal PrintE guesses PutE RETURN end of PROC tally PROC playgame CARD numguesses tbe number of guesses ctr counter used in delay loop BYTE num the number to guess guess the user s guess PrintE I m picking my number FOR ctr 0 TO 450 delay used to make the user DO thiink the computer is picking OD a number PutE PrintE OK here we gol PutE Num Rand 101 get the number to guess Numgueeses 0 set number of guesses to 0 DO start of UNTIL loop Print What s your gu
10. checks are made so we don t recommend that you use code block unless you know quite a bit about assembly and machine language The format for a code block is lt value gt lt value gt where lt value gt is one of the values In the code blocks It must be a compiler constant see section 3 2 If it is greater than 255 then it is stored in LSB MSB order Examples 40 0D 51 FO 600 BYTE b1 b2 b3 A b1 342 b3 4 A7 DEFINE on 1 54 on on t FFFa Code blocks are useful for including small machine code routines but it s too much trouble to insert a large one If you want to use a lot of machine code routines see section 9 4 for some hints 9 2 Addressing Variables In sections 3 4 1 8 1 1 and 8 2 1 Fundamental POINTER and ARRAY variable declarations we showed that a variable s address could be specified when that variable was declared but we didn t really make use of that option We didn t even explain the usefulness of doing this This option allows you to declare an ACTION variable which has the same address as any hardware register Then you can manipulate graphics and sound directly change operating system characteristics etc To illustrate the advantages of this we re going to present a graphics program which makes the background color change and scroll To do this we can t use the normal shadow color registers because they re only looked at every T V frame Instead we ll directly manipu
11. command NOTE the parentheses around lt arith exp gt are always required in the RETURN statement The above is a simple example Functions can be used to do quite complicated operations but even the most convoluted functions must follow the format outlined In this section 6 2 2 RETURN As you probably noticed in the format of the FUNCtion declaration the RETURN isn t used in the same way as in PROCedure declarations In functions it is followed by lt arith exp gt This feature allows a function to return a value If you tried to put lt arith exp gt after the RETURN ina procedure declaration you would get an error because procedures can t return a value Although there are dissimilarities between RETURNS in functions and procedures there is one convenient similarity you may have more than one RETURN in both procedures and functions The following example shows usage of multiple RETURNs in a function Scenario Example 1 in the function declaration section 6 2 1 returned the square of a CARD but it did no checking for overflow If you squared 256 you would get 65536 1 greater than the maximum CARD value allowed There are two ways to fix this problem 1 Require that the number being squared be of BYTE type thus making it impossible to enter a number greater than 255 2 Check for overflow in the function itself The following example illustrates the second method CARD FUNC square CARD x This
12. lt value list gt lt str const gt lt value list gt lt value gt lt value list gt lt value gt lt value gt lt comp const gt Variable Declaration for Records lt record decl gt lt identifier gt lt rec ident list gt lt rec ident list gt lt rec ident gt lt rec ident list gt lt rec ident gt lt rec ident gt lt identifier gt lt address gt lt address gt lt comp const gt A 5 Variable References Memory References lt mem reference gt lt mem contents gt lt identifier gt lt mem contents gt lt fund ref gt lt arr ref gt lt ptr ref gt lt rec ref gt lt fund ref gt lt identifier gt lt arr ref gt lt identifier gt lt arith exp gt lt ptr ref gt lt identifier gt lt rec ref gt lt identifier gt lt identifier gt A 6 ACTION Routines lt routine list gt lt routine gt lt routine list gt lt routine gt lt routine gt lt proc routine gt lt func routine gt Procedure Structured lt proc routine gt lt PROC decl gt lt system decls gt stmt list gt RETURN lt proc decl gt PROC lt identifier gt lt addr gt lt param decl gt lt addr gt lt comp const gt Function Structure lt func routine gt lt FUNC decl gt lt system decls gt lt stmt list gt RETURN lt arith exp gt lt FUNC decl gt
13. nunber 4365 What is your employment level L In what year did you start working here 1975 O K Here s what have I D 4365 Level L Entry year 1975 The is used to notify the compiler that you are making a record reference and is only validin record references From the above program example you can see that the format of a record reference is lt record name gt lt f ield name gt Note that lt field name gt and lt record name gt are defined in different declaration statements as shown in the previous section lt field name gt is defined in the TYPE declaration when you define the fields of a record type whereas lt record name gt is defined in a variable declaration when you declare the variable to be of a record type 8 4 Advanced Use of the Extended Types The extended data types seem to be limited by the fact that they may only operate on the fundamental types that is you cannot have arrays of records an array field in a record etc However there are ways to get around these limitations as seen in example 4 section 8 2 3 In that example we created an array of pointers by using the elements of a CARD array as pointers not cardinal numbers In this section we ll demonstrate some other ways to get more out of the extended types including a program using records with array fields and another program which uses an array of records But you just said that was illegal It is illegal if you
14. pointer means something very similar Pointers contain a memory address and so point to a memory location You can change the value of a pointer and make it point to a new place just like moving the weatherman s pointer to another place on the map The big difference is that he points to cities or states whereas ACTION pointers can point to BYTE CARD or INT values Somehow we have to let the compiler know what type of value we want a given pointer to point to The declaration section will show you how to do this After we ve gone over the method used to declare a pointer we ll show you how it can be used This is done in the manipulation section through the use of program examples 8 1 1 Pointer Declaration The format used to declare a pointer looks quite similar to the format of fundamental data type variable declarations except that we tell the compiler that the variable Is a pointer and not just a fundamental data type lt type gt POINTER lt ident gt lt addr gt lt ident gt lt addr gt where lt type gt is the fundamental type of the information the pointer points to POINTER is the keyword used to show that the variables declared are Pointers lt ident gt is the name of the pointer variable lt addr gt tells where in memory you want the pointer to point to initially It must be a compiler constant Because a pointer variable actually contains an address it must be able to take on values ranging
15. 0600 0000 0 0 1538 0602 0000 0 0 1539 0603 0000 0 0 1540 0604 0000 0 0 1541 0605 0000 00 1542 0606 0000 0 0 1543 0607 0000 0 0 1544 0608 0000 00 1545 0609 0000 0 0 1546 060A 0000 0 0 1547 060B 0000 0 0 Chapter 3 Program Debugging Facilities You have probably written programs which have not work the way that you expected not because of syntax errors but simply because something you re doing or think you re doing isn t executing properly With the ACTION Monitor and its options menu you can debug your program step by step to determine where the error is occurring The TRACE Option One of the options available in the options menu is Trace If this option is enabled Y you can follow your program s execution When the trace is on every time a routine is called its name and parameters are displayed on the screen You might be able to discover what is going wrong simply by looking at the order of the routine calls and or the parameters being passed If this is so fantastic If not you probably need to do some major debugging The first thing you need to do before doing any major debugging is to stop your program sometime during its execution There are two ways to do this in ACTION I The lt BREAK gt key and the Library routine Break The lt BREAK KEY gt Although the lt BREAK gt key is disabled during use of the ACTION Editor it i
16. 1 THEN lt statement1 gt ELSEIF cmd 2 THEN lt statement2 gt ELSEIF cmd 3 THEN lt statement3 gt Fl RETURN Note the RETURN after the first condition which tests for Illegal input You don t want to go through all the command tests if the command isn t a valid one so you just print your error message and hop out of the procedure with a RETURN Voila 6 1 3 Calling Procedures You ve already seen some procedure calls although you probably don t know it Almost every time we used a library routine in an example we were making a procedure call The format is simple enough lt identifier gt lt parameter list gt where lt identifier gt is the name of the procedure you want to call lt parameter list gt contains the values you want to send to the procedure as parameters Here are a couple of examples don t worry about the parameters for now a whole section is devoted to them later PrintE Welcome to Joe s Deli the only PrintE Computerized deli in the world factorials gueasuniil BYTE z CARD add signoff add z Of course you must already have declared the procedures factorials gueseuniil and signof before using them here PrintE is a library procedure so it s not declared by you but is declared in the ACTION Library Notice that the parentheses are required even when the procedures have no parameters When a procedure you call has parameters the call must have no m
17. 2 Setting the Line Length As mentioned in the first paragraph of section 2 3 you can set the maximum line length You can find out how to do this in part IIl section 2 5 so we need not show you here 2 4 Cursor Movement To move the cursor left one character press lt CTRL gt lt left arrow gt To move the cursor right one character press lt CTRL gt lt right arrow gt To move the cursor up one line press lt CTRL gt lt up arrow gt To move the cursor down one line press lt CTRL gt lt down arrow gt The commands above are simply the normal cursor movement Keys the Atari screen editor understands The ACTION Editor however allows you some more cursor movement commands designed to increase your program writing speed You can make the cursor go to the beginning of the line its on by pressing lt CTRL gt lt SHIFT gt lt and go to the end of the line by pressing lt CTRL gt lt SHIFT gt gt These two commands will take you to the true beginning or end of the line even if it the beginning or end is not visible in the window The line will simply be shifted over so that it again the beginning or end is visible in the window When you move the cursor off the shifted line the line will be moved back to its proper position You can go to the beginning of the file by pressing lt CTRL gt lt SHIPT gt H 2 4 1 Tabs You can move the cursor to the next tab stop by pressing lt TAB gt To set a tab stop
18. 4 5 Both and lt gt mean the same thing to ACTION so you may use the one you prefer AND and OR are special relational operators and are discussed in Complex Relational Expressions section 4 4 TECHNICAL NOTE the ACTION Compiler does comparisons by subtracting the two values in question and comparing the difference to 0 This method works correctly with one exception if you are comparing a large positive INT value with a large negative INT value the outcome could be wrong since INTs use the highest bit as a sign bit 4 1 4 Operator Precedence Operators require some kind of precedence a defined order of evaluation or we wouldn t know how to evaluate expressions like 4 5 3 Is this equal to 4 5 3 or 4 5 3 Without operator precedence it s impossible to tell ACTION s precedence is very precise but can be circumvented by using parentheses since they have the highest precedence In the following table the operators are listed in order of highest to lowest precedence Operators on the same line have equal precedence and are evaluated from left to right in an expression see examples Table 7 Operator Precedence Highest to Lowest Parentheses Unary minus address of MOD LSH RSH Multiply Divide Modulus Shifts Addition and Subtraction f lt gt gt gt lt lt Relational Operators AND amp Logical bitwise AND OR Logical Bitwai
19. BYTE row parameters col is the horizontal column number of the position desired row isthe vertical row number of the position desired description This procedure sets the cursor location to the specified position in any graphics mode The library routines Print Put Input and Get use the cursor registers this command sets when doing their respective functions 5 8 BYTE FUNC Locate purpose determine the color or character at a given screen location format BYTE FUNC Locate CARD col BYTE row parameters col is acolumn number valid in the current graphics mode row is a row number valid in the current graphics mode description This routine retrieves the ATASCIT code of the character or the number of the color at the specified location The registers this routine uses are incremented so as to point to the adjacent horizontal position the first position in the next line if you Located the last position ona line All of the Get Put Print and Input routines also use these registers as references for the current cursor location so you can use this to move to any position and then use another routine to manipulate what s there 5 9 PROC Sound purpose format parameters description to enable the sound capabilities of the ATARI PROC Sound BYTE voice pitch distortlon volume voice is one of the four voices available on the ATARI 0 3 pitch is the frequency of the sound The lower the number is the h
20. Lines 2 5 4 Inserting Lines 2 5 5 Breaking an __Recombining Lines 2 5 6 Substituting Text 2 5 7 Restoring a Changed Line 2 6 Windows 2 6 1 Window Movement 2 6 2 Creating a Second Window 2 6 3 Moving Between Windows 2 6 4 Clearing a Window 2 6 5 Deleting a Window 2 7 Moving Copying Blocks of Text 2 8 Tags Chapter 3 Comparing ACTION and Atari Editors 3 1 Identical Commands 3 2 Differing Commands 3 3 Commands Unique to ACTION Chapter 4 Technical Considerations 4 1 Files from Other Text Editors 4 2 Key Recognition 4 3 Out of Memory Error Part Il The ACTION Editor Chapter 1 Introduction The Editor is where you create new ACTION programs and edit old ones If you have used a program editor before you will notice that the ACTION Editor is far more sophisticated than most others in fact it could almost be called a word processor because it does so much Although it is capable of many things you will find that the ACTION Editor is easy to work with If you have never been exposed to anything but the Atari screen editor then you are in for pleasant surprise You can use the ACTION Editor for any editing you want to do not just editing ACTION programs You could do all your editing correspondence programs in other languages etc 1 1 Special Notations and Vocabulary USAGE OF SINGLE QUOTE MARKS Unless format and context make the use of quotes unnecessary commands and special characters will be
21. MODULE 7 Compiler Directives 7 1 DEFINE 7 2 INCLUDE 7 3 SET 8 Extended Data Types 8 1 POINTERS 8 1 1 Pointer Declaration 8 1 2 Pointer Manipulation 8 2 ARRAYS 8 2 1 Array Declaration 8 2 2 Internal Representation 8 2 3 Array Manipulation 8 3 Records 8 3 1 Declaring Records 8 3 1 1 The TYPE Declaration 8 3 1 2 Declaring Record Variables 8 3 2 Record Manipulation 8 4 Advanced Use of Extended Types Chapter 9 Advanced Concepts 9 1 Code Blocks 9 2 Addressing Variables 9 3 Addressing Routines 9 4 Assembly Language and ACTION 9 5 Advanced Use of Parameters PART IV The ACTION Language Chapter 1 Introduction The ACTION language is the heart of the ACTION System It incorporates the good points of both C and PASCAL and at the same time is the fastest high level language available for ATARI home computers If you have a background in BASIC or some other unstructured language you will find ACTION a welcome change because its structure is similar to the way we structure ideas in our own minds You can actually look at an ACTION program someone else has written and understand what is going on without having to wade through a thousand GOTOs and undeclared variables Program structure is simple in ACTION because programs are built component by component The components are groups of related statements which accomplish some task When you have written components for all the tasks required in your program it is
22. U variable Used in routine VARIABLE PROC PROC PROC PROC PROC NAME SCOPE playgame intro tally stop main numgames global A A A U A A U goal global A U A U A U A A beatgoal global A U A A U A A numguesses local A U num local A U guess local A U ctr local A U again local A U ctr local A U You can see that the global variables are available for use in every one of the routines whereas the local variables are available only in the routine in which they are declared Notice that there are two local variables called ctr one in PROC playgame and the other in PROC intro Although they have the same name these two variables are not the same just as neat meaning clean and neat meaning undiluted were not the same earlier The two ctr s have different local scopes because they are declared in two different procedures 6 4 Parameters Parameters allow you to pass values into a routine You may wonder wliy this is necessary since you could use global variables for passing values into and between routines Well there are two reasons that parameters exist 1 They make your routines capable of multipurpose use 2 They allow you to manipulate variable values within a routine without changing the value of any global variable We ll discuss each of these advantages separately following the above order but first we should give the format of a parameter list for those of
23. You should assume the existence of appropriate line numbers in most cases In the ACTION examples shown assume the following variable declarations INT i j k CARD c d e BYTE a b BYTE ARRAY s t aa ba CARD ARRAY ca da ea INT ARRAY ia ja ka BASIC statements ACTION equivalents C D A c d i a IF A lt gt 0 THEN B 1 IF a lt gt 0 THEN b 1 FI 10 IF A 0 THEN 30 IF a lt gt 0 THEN b 1 c a 2 20 B 1 C A 3 FI 30 REM 10 IF A 0 THEN B 1 GOTO 30 IF a 0 THEN b 1 ELSE b 7 FI 20 B 7 30 REM FOR l 1 TO 100 FOR i 1 TO 100 DO OD NEXT PRINT HELLO PrintE HELLO PRINT HELLO Print hello PRINT 5 HELLO PrintDE 5 HELLO PRINT 5 HELLO PrintD 5 HELLO PRINT PrintlE i PRINT l PrintF l I E 1 or Print l PrintlE l PRINT 3 B 3 PrintBD 3 b 3 INPUT Put Inputl Note the use of tbe optional colon s inthe ACTION example Colons ignored by ACTION and so may used as statement separators INPUT B Put InputS ba PUT 0 65 Put A or Put 65 or Put 41 GET C B b GetD c OPEN 1 4 0 K Open 1 K 4 0 CLOSE 3 Close 3 NOTE 1 C B Note 1 c b POINT 1 C B Point 1 c b XIO 18 6 0 0 S XIO 6 0 18 0 0 S or see also the Fill library routine B PEEK C b Peek c or in better ACTION
24. a whole line place the cursor on the line you want deleted and press lt SH1FT gt lt DELETE gt The succeeding lines move up to fill the empty space 2 5 4 Line Insertions To insert a blank line above the line the cursor is on press lt SHIFT gt lt INSERT gt The succeeding lines move down to allow space for the new blank line 2 5 5 Breaking amp Recombining Lines To break a single line into two adjacent lines first position the cursor on the character you want as the first character in the second line and then press lt CTRL gt lt SHIFT gt lt RETURN gt NOTE if you are in Insert mode simply position the cursor and press lt RETURN3 gt Succeeding lines of text are moved down to allow room for the new line To combine two adjacent lines into a single line first position the cursor on the first character in the second line and then press lt CTRL gt lt SHIFT gt lt BACK S gt Succeeding lines are moved up to fill the empty space 2 5 6 Substituting Text The ACTION Editor allows you to substitute a new string for an old one You are prompted for the new string and then for the old one The Editor searches for the first occurrence of the old string starting at the cursor position and replaces it with the new string To begin this command press lt CTRL gt lt SHIFT gt S The message area will display the prompt Substitute If you have previously used this command you will see the la
25. amt CARD fact 1 the factorial of num num 1 the counter amt 6000 the upper bound Print Factorials less than PrintC amt prints the upper bound PrintE print a and carriage return PutE sprints a carriage return WHILE fact num lt amt test next factorial DO start of WHILE loop fact num PrintC num sprint the number Print factorial PrintCE fact sprint number s factorial Num 1 increment number OD send of WHILE loop RETURN end of PROC factorials Output 1 Factorials less than 6000 1 factorial is 1 2 factorial is 2 3 factorial is 6 4 factorial is 24 5 factorial is 120 6 factorial ie 720 7 factorial is 5040 PROGRAMMING NOTE If you go Over Factorials less than 40000 you will discover that the compiler does no overflow error checking because you ll see the output wrap around that is you ll get a number larger than the maximum a CARD allows 65 535 and start at zero again If you got up to say 66000 the output would show 66000 65536 464 because it went as high as it could go and then wrapped around The technical term for this kind of thing is overflow and you can find out more about it in Part IV The ACTION Compiler Example 2 PROC guesswhlle This procedure plays a gueesing game with the user using a WHILE loop to keep the game going BYTE nuiti the number to guess guess 200 guess is initialized to an impossil5
26. at the beginning and a funny RETURN statement at the end Below is a diagram of the construction PROC lt identifier gt lt addr gt parameter list gt lt variable declarations gt lt statement list gt RETURN where PROC is the keyword denoting a procedure declaration lt identifier gt is the name of the procedure lt addr gt optionally specifies the starting address of the procedure See 9 3 parameter list gt is the list of parameters required by the procedure see section 6 4 for an explanation of parameters lt variable declaration gt is the list of variables declared local to this procedure see 3 4 1 for variable declaration and 6 3 for scope of variables lt statement list gt is the list of statements In the procedure RETURN denotes the end of the procedure see next section NOTE lt paramet r list gt lt variable decl gt and lt statem nt list gt are all optional You will probably use at least some of them but the following would be a valid procedure declaration PROC notbing the parenthesee ARE required RETURN It does nothing but this type of empty procedure is useful when you are writing a program made up of many procedures If for example you have written a program that calls a procedure named dotest but you haven t yet written dotest you could make it an empty procedure so you could test the rest of the program without getting an Undeclared Variable error Don t
27. because they do things that make the examples more visually instructive Output 1 1 times two equals 2 2 times two equals 4 3 times two equals 6 4 times two equals 8 5 times two equals 10 6 times two equals 12 7 times two equals 14 8 times two equals 16 The dot dot dot at the end of the output shows that this will go on forever or until you press the lt SYSTEM RESET gt key On its own a DO OD loop is more or less useless but when used in conjunction with the loop controlling statements FOR WHILE and UNTIL it becomes one of the most useful statements available NOTE hitting the lt BREAK gt key would also get you out of the loop in example 1 because the loop is doing a lot of I O lt BREAK gt only works when doing a lot of 1 0 See Part IV The ACTION Compiler for more information Whenever you see lt D0O OD loop gt in the fromats of the loop controlling statements remember that it means a loop and that in turn means a DO OD pair surrounding the loop 5 2 3 2 EXIT Statement The EXIT statement is used to hop gracefully out of any loop This statement will cause program execution to skip to the statement following the next OD Here s an example Example 2 PROC timestwo CARD i 0 j DO start of DO OD loop l 1 add 1 to i J i 2 set j equal to i 2 PrinteC i Print times 2 equals EXIT Here s the EXIT statement PrintCE j OD send of DO OD loop
28. being nothing This with substitute the old string with nothing and so in effect delete it 2 5 7 Restoring a Changed Line The ACTION Editor allows you to restore a line to its previous form if you have made an error while editing it To do this you must remain on the changed line and press lt CTRL gt lt SHIFT gt U WARNING if you leave the line and then come back to it this command will not work because the Editor only remembers what the line was before you started editing it while you remain on the line If you have accidentally deleted a whole line you can retrieve it by pressing lt CTRL gt lt SHIFT gt P More information about this command may be found in section 2 7 NOTE the tags on the changed or deleted line are not restored 2 6 Windows The displayed contents of the central portion of the screen is called a window The following five sections describe the Editor commands used to manipulate create and delete windows In these sections we use the term current window to mean the window which the cursor is in 2 6 1 Window Movement You can make the window scroll up or down one line simply by moving the cursor If you try and move the cursor off the top of the screen the window moves up one line to keep the cursor on the screen The same works with the bottom of the screen This type of vertical scrolling could take a long time if your program were big so the Editor also allows you to make the window scroll
29. by the size of the window itself To move up one window press lt CTRL gt lt SHIFT gt lt up arrow gt For the sake of continuity what was the top line in the old window is now the bottom line of the new window To move down one window press lt CTRL gt lt SHIFT gt lt down arrow gt For the sake of continuity what was the bottom line in the old window is now the top line of the new window The Editor also allows you to scroll the window horizontally Thatis you can make the window s left margin start at any column instead of the first column Ifa line is longer than the window if it extends beyond the left or right bounds of the window the character at the edge of the window is shown in inverse video to make you aware of this To move the window one character to the right pressi lt CTRL gt lt SHIFT gt To move the window one character to the left press lt CTRL gt lt SHIFT gt 2 6 2 Creating a Second Window When you first enter the ACTION Editor there is only one window You can create a second window by pressing lt CTRL gt lt SHIFT gt 2 The screen will now look like this Sa a ea cocaine cae ae ACTION c 1993 ACS Sp la alt cl arin sina tlre eee See ee ce a ere oa The window above the message area is window 1 and the window below it is window 2 You can use each window Independently so you could be
30. from 0 to 65535 0 to FFFF since an ATARI with 64k of memory has that many separate memory locations Pointers are stored as a two byte unsigned numbers in LSB MSB order to allow this range That means that they are stored as CARDs except that they can be interpreted as addresses Since the use of pointers is dealt with in the next section we ll just give some sample pointer declarations instead of whole program examples BYTE POINTER ptr declares ptr as a pointer to a BYTE value CARD POINTER cpl _ declares cpl as a pointer to a CARD INT POINTER ip 8000 declares ip as a pointer to an INT and points it to memory location 8000 6 1 2 Pointer Manipulation Pointers can be used to manipulate a variety of things in ACTION for the simple reason that they can easily be made to point to different memory locations This makes cataloguing and tabulating information very easy The program on the following page is just a simple example to give you an idea of what a pointer actually does It will introduce the address operator used with pointers after the example we ll discuss the in depth Example 1 PROC pointeruaage BYTE num E0 declare and place two Chr E1 BYTE variables BYTE POINTER bptr declare a pointer to BYTE type Bptr num make bpir point to num Print bptr now points to address PrintF H bptr sprints out num s address PutE Bptr 255 puts 255 into the location bptr points t
31. get to the statement just before the OD This UNTIL controls the infinite loop using the outcome of the conditional expression If lt cond exp gt is true then execution will continue at the statement after the OD otherwise it will loop back up to the DO Notice that the until must be the statement directly before the OD A program example should clarify this somewhat 1 PROC gueesuntil This procedure plays a guessing game with the user using an UNTIL loop BYTE num the number to guees guess the user s guess PrintE Welcome to the guessing game I m PrintE thinking of a number from 0 to 100 num Rand 101 get the number to guess DO start of UNTIL loop Print What is your guess Guess inputB get the user s guess IF guess lt num THEN guess too low PrintE Too low try again ELSEIF guess gt num THEN guess too high PrirtEt Too high try again ELSE guess just right PrintE Congratulations PrintE You got it Fl end of guess testing UNTIL guess num floop control OD end of UNTIL loop RETURN end of PROC guessuntil Output 1 Welcome to the guessing game l m thinking of a number from 0 to 100 What s your guesa 50 Too low try again What s your guees 60 Too high try again What s your guess 55 Too low try again What s your guess 57 Congratulations You got it This is the same example as in the WHILE section but this time implemented
32. is designed so that your program can be read easily It allows lines up to 240 characters long even though the window only shows 38 characters at a time so you can use indentation to clarify your program without worrying about making lines too long The Editor also allows blank lines SO you can separate the components of your program with white space NOTE you also have control over the maximum line length so you pick a line length you think best or will fit on your printer The Editor even buzzes when you reach the limit to let you know it s time to go to the next line NOTE if a text line is longer than the window if it extends beyond the left or right bounds of the window the character at the edge of the window is shown in inverse video to make you aware of this FIND and SUBSTITUTE The Editor allows you to search for a given string and will move the cursor to the first match found in the program The Editor also allows an extension of this You can tell it to search for a given string and then replace the first match with another string you specify all with one command MOVING TEXT BLOCKS Have you ever entered a program and wished that a group of lines which you entered at one location could be conveniently moved to another location In ACTION this is a snap Saving those lines called a text block in the copy buffer that s where a text block is temporarily saved allows you to move the cursor to where you want
33. lt IF stmt gt IF lt cond exp gt THEN lt stmt list gt lt ELSEIF exten gt lt ELSE stmt gt FI lt ELSEIF exten gt ELSEIF lt cond exp gt THEN lt stmt list gt lt ELSE exten gt ELSE lt stmt list gt DO OD Loop lt DO loop gt DO lt stmt list gt lt UNTIL stmt gt OD UNTIL statement lt UNTIL stmt gt UNTILE lt cond exp gt WHILE Loop lt WHILE loop gt WHILE lt cond exp gt lt DO loop gt FOR Loop lt FOR loop gt FOR lt identifier gt lt start gt TO lt finish gt STEP lt inc gt lt Do loop gt lt start lt arith exp gt lt finish gt lt arith exp gt lt inc gt lt arith exp gt Code Blocks lt code block gt lt comp const list gt lt comp const list gt lt comp const gt lt comp const list gt lt comp const gt A 8 Expressions Relational Expressions lt complex rel gt lt complex rel gt lt special op gt lt simp rel exp gt lt simp rel exp gt lt simp rel exp gt arith exp gt lt rel op gt lt arith exp gt lt arith exp gt Arithmetic Expressions lt arith exp gt lt arith exp gt lt add op gt lt mult exp gt lt mult exp gt lt mult exp gt lt mult exp gt lt mult op gt lt value gt lt value gt lt value gt lt num const gt lt mem reference gt lt arith exp gt Appendix B ACTION Memory Map
34. monitor commands are summarized in chapter 2 Below the command line is the message area The message area is the large outlined block in the middle of the screen Itis a multi purpose area When a program is running it is used to display program results It can also be used to trace program execution see the options menu choice trace in chapter 2 When either the operating system or the ACTION compiler finds an error the message area contains the error number and the program text around the line where the error was found In its role as the command center of ACTION you can move from the ACTION monitor to any of several different ACTION functions To get an idea of the relationship between the various ACTION parts see the diagram on the preceding page You can execute a compiled ACTION program see the ACTION Monitor s RUN command in Chapter 2 You can also call the ACTION Editor described In Part II or call the ACTION Compiler described in Part V If you are using disk drives you can even call the DOS see the ACTION monitor DOS command mentioned in Chapter 2 Chapter 2 ACTION Monitor Commands 2 1 BOOT Restarting ACTION Sometimes you need to restart ACTION from the ACTION Monitor This might occur after a fatal error or upon return from DOS You can restart ACTION by entering BOOT then pressing lt RETURN gt Examples BOOT lt RETURN gt B lt RETURN gt WARNING text in the ACTION Editor
35. move the cursor where you want the tab and then press lt SHIFT gt lt SET TAB gt To clear a tab stop move to the tab stop you want cleared and press lt CTRL gt lt CLR TAB gt 2 4 2 Finding Text The Editor allows you to find a specified string of characters 1 32 and can be very useful when skipping from place to place in your file To do this enter the command lt CTRL gt lt SHIFT gt F The message area will prompt you with Find If you have previously used the Find command you will see the string you last tried to find following the prompt If you want to find the next occurrence of this string simply press lt RETURN gt If you want to find a different string type in the new string and press lt RETURN3 gt You will notice that the old string disappears as soon as you start typing If this is the first time you are using the Find you will see nothing following the prompt and you should type in the string you want found and press lt RETURN gt This command will start at the current cursor position and look for the first occurrence of the string you specified If the string is found the Editor will move the cursor to the first character in the found string and make the window move to display the surrounding section of text If the string isn t found the message area will display the line not found 2 5 Correcting Text The following six sections will give you information on how to correct and de
36. newrecord BYTE POINTER nameptr _ pointer to name field BYTE continue DO newrecord idarray reccount recordsize Print l D number newrecord idnum InputC get I D number Print Employment level A Z newrecord level GetD 7 employtnent level Print Access code newrecord codenum InputC get secret code nameptr newrecord nameoff set pointer nameptr to PrintE Employee s name start of name field Print form Last First InputS nameptr read name into name field reccount 1 PutE Print Input another record Y or N continue GetD 7 PutE UNTIL continue N OR continue n OD RETURN EXAMPLE 2 NOTES As in the previous example there are some program lines which need explanation including nameoffset 5 BYTE POINTER nameptr nameptr newrecord nameoffset Inputs nameptr Before discussing the lines individually let s go over the method used to put the name into the array of records First of all we need to find where to put the name once we ve read it in then we need to figure out a way to read the name in The explanations of the above statements show you how we do it nameoffset 5 This DEFINEs the distance you have to go into a single record to get to the first byte of the string and is used when getting the pointer to the string to point to the right position BYTE POINTER nameptr This pointer is used to point to the first byte of the name field i
37. or dividing by 2 4 2 Type Compatibility and Boundary Checking You must also be careful because the ACTION compiler supports no boundary checking of simple variables or ARRAYS This is deliberately done in order to allow you more flexibility in your data manipulation The price for this freedom is increased vigilance You must set up and maintain your own procedures for checking boundary limits and the error handling responses This is another good place for a standard set of subroutines which can be iNCLUDEd 4 3 Channel 7 Restriction When you enter the ACTION system It opens channel 7 for reading from the keyboard K You may use this channel for this purpose bot do not alt er its attributes by reOpening or Closjng it NOTE if you do make use of channel 7 and assume that its already open your programs will not run without the ACTION cartridge 4 4 Available space You might be working on a big program and suddenly find that you are out of space When this happens you can do one of three things depending on what you are doing at the moment when the error appears If you are Editing Immediately save your file lt CTRL gt lt SHIFT gt W go to the Monitor and reboot the system BOOT you may go back to the Editor and read your file back in If you are Compiling Go to the Editor and save your program Thengo back to the Monitor reboot the system and Compile your program from the storage device disk cassett
38. pointer reference This method involves some indirection i e using a pointer to a variable instead of the variable itself but is very efficient and useful in some cases as the following example shows Example 1 BYTE FUNC substr BYTE ARRAY str sub BYTE POINTER errptr notfound This function will search str looking for the substring sub If it s found the function returns the index onto the string If the substring is slonger than the main string an error is returned via pointer If the substring sisn t found that is returned via another pointer BYTE ARRAY tempsir sholds temporary substring for test BYTE Ctrl outer loop counter ctr2 slinnar loop counter IF sub 0 gt str 0 THEN substring bigger than string errorptr 1 ELSE FOR ctrl 1 TO str 0 loop to check string DO IF sub 1 str ctr THEN testing 1st characters tempstr 0 sub 0 dimension tempstr FOR ctr2 1 TO sub 0 fill tempstr DO tempsir ctr2 str ctr2 ctrl 1 fill tempstr OD IF SCompare tempstr sub 00 THEN compare 2 strings RETURN Ctrl sreturn index if equal Fl Fl end of testing 1st chsractere OD end of FOR loop Fl notfound 1 didn t RETURN in loop so no match found RETURN 0 end of FUNC substr Now when we want to call this we must use the forn lt index gt substr lt string gt lt substring gt lt errptr gt lt nofindptr gt where lt index gt is the index into lt string gt where substring starts lt s
39. s your guess 60 Too high try again What s your guess 55 Too low try again What s your gueas 57 Congratulations You got it If you look back at the above example you ll see RETURN as the last statement We ll now cover why it s there 6 1 2 RETURN RETURN is used to tell the compiler to leave the procedure and return control to whatever called the procedure If your program calls a procedure execution will continue with the statement after the procedure call If you are compiling a single procedure or a one procedure program control will be returned to the ACTION Monitor WARNING the compiler cannot detect a missing RETURN Strange and disastrous things can happen if you leave out a RETURN This also goes for RETURNS at the end of functions as well There can be more than one RETURN in a procedure For example if your procedure has an IF statement with lots of ELSEIFs you might want to RETURN after one or more of the ELSEIF cases The example on the following page illustrates this possibility PROC testcommand This procedure tests a command to see if it is valid Valid commands sare 0 1 2 and 3 If the command is none of these an error message sis printed and control is returned to whatever called this procedure BYTE cmd Print Command gt gt cmd InputB IF cmd gt 3 THEN PrintE Command Input ERROR RETURN get out before command tests ELSEIF cmd 0 THEN lt statement0 gt ELSE IF cmd
40. see 2 3 2 for more information If you want to type a control character you must press the lt ESC gt before doing so This lets the Editor know that the control character should be interpreted as text and not as an Editor command What happens when try to type over something I ve already written The ACTION Editor allows you two options in this case Text can be entered in either Replace or Insert mode When in Replace mode the text you enter will overwrite whatever was there before replacing the old with the new character by character When in Insert mode the text you enter will be inserted wherever the cursor is and move all the previous text over without overwriting it The Editor command lt CRTIL gt lt SHIFT gt I allows you to change from one mode to another When you use this command the mode you have changed to will be printed in the message area see section 2 5 2 for more information NOTE the Editor is in Replace mode when you first enter it If you want to erase all the text in a file just put the cursor into the window you want to clear and press lt SHIFT gt lt CLEAR gt This will clear not only what you see in the window but the entire file see section 2 6 4 for more Information 2 3 1 Text File I O If there were no way to save the program in the Editor buffer you would have to retype it every time you wanted to use it The Editor allows you both to read and to write files to any peripher
41. statements a valid use of arithmetic expressions Function calls can be used in any arithmetic expression with one exception Functions calls may NOT be used in an arithmetic expression when that expression is used as a parameter in a routine call or declaration Example X square 2 Rand 50 INVALID Here are some examples of valid function calls x 5 Rand 201 c square x 100 x IF ptr lt gt Peek 8000 chr uppercaae chr Peek and Rand are library functions so they needn t be declared by you but square and uppercase are user written functions and so they must be declared before they are called here PROGRAMMING NOTE although it is not recommended you can call functions as though they were procedures If you do this the value returned is ignored 6 3 Scope of Variables The term Scope of a Variable is used to express the range of a variable s legitimacy To help you understand what this means let s apply the concept of Scope to a more familiar situation the English language Below is a table of British English words followed by their American English equivalent British American BONNET HOOD LORRY TRUCK LIFT ELEVATOR FAG CIGARETTE Each pair of words means the same but the words scopes are different Bonnet when used to mean the moveable cover over an auto s engine is legitimate only when used in countries that speak the King s English Hood on
42. string to the default channel with a lt RETURN3 gt at the end PrintD outputs the string to a specified channel without a lt RETURN gt at the end PrintDE outputs the string to a specified channel with a lt RETURNS gt at the end Their usage is very straightforward and simple but you must remember that with the procedures which require a channel the channel must first be opened 2 1 2 Printing BYTE Numbers The following four procedures are used to print BYTE type data in decimal format They start with the PrintB base and then add the possible options purpose to output one byte of data as a decimal number formats PROC PrintB BYTE number PROC PrintBE BYTE number PROC PrintBD BYTE channel number PROC PrintBDE BYTE channel number parameters number is an arithmetic expression remember that arithmetic expressions can simply be a const int or variable name channel is a valid channel number 0 7 description The above procedures output BYTEs as follows PrintB outputs the byte to the default channel without a lt RETURN gt at the end PrintBE outputs the byte to the default channel with a lt RETURN3 gt at the end PrintBD outputs the byte to a specified channel without a lt RETIJRN gt at the end PrintBDE outputs the byte to a specified channel with a lt RETURN3 gt at the end 2 1 3 Printing CARD Numbers purpose to output numbers as CARDs in decimal format formats PROC PrintC C
43. the expression woul lt l equal 12 4 3 12 ACTION has two types of expressions arithmetic and relational The example given above is an arithmetic expression Relational expressions are those which involve a true or false answer 5 gt 7 is false if we take gt to mean is greater than or equal to This type of expression is used to evaluate conditional statements see section 5 2 1 A conditional statement in every day life might be If it Is five o clock or later then it s time to go home An ACTION relational expression for this might be hour gt 5 You yourself make this check and many others automatically when you look at a clock but the computer needs to be told exactly what to check for Before going into the expressions themselves we need to define the operators that apply to each type of expression After that we ll discuss each expression and then go into some special extensions of relational expressions 4 1 Operators ACTION supports three kinds of operators 1 Arithmetic operators 2 Bit wise operators 3 Relational operators As suggested by the names of the first and last they specifically pertain to an expression type The second class of operators performs arithmetic and addressing operations at bit level 4 1 1 Arithmetic Operators The arithmetic operators are those we commonly use in math but some are modified so that they can be typed in from a computer keyboard Here i
44. the description of each routine best illustrates its usage we ll jump right into the routines themselves without further discussion 5 1 PROC Graphics purpose to enable bit map ATARI graphics format PROC Graphics BYTE mode parameters mode is the number of the graphics mode as in the BASIC Graphics routine see table below description This procedure is exactly equivalent to the BASIC command of the same name and allows you access to the many varied graphics modes available on the ATARI The following table gives some information about the 9 base graphics modes These modes are all split screen to get full screen add 16 to the base mode number to preserve the current screen as you change modes add 32 to the base mode number to get both of these options add 48 to the base mode number Graphics Mode Rows split full Number of Mode Type Columns Columns Colors 0 Text 40 NA 24 2 1 Text 20 20 24 5 2 Text 20 10 12 5 3 Graphics 40 20 24 4 4 Graphics 80 40 48 2 5 Graphics 80 40 48 4 6 Graphics 160 80 96 2 7 Graphics 160 80 96 4 8 Graphics 320 160 192 1 2 5 2 PROC SetColor purpose sets the specified color register to the color given by hue and luminance format PROC SetColor BYTE register hue luminance parameters register is one of the five color registers 0 4 hue is the hue of the color luminance is the luminaire of the color descripti
45. the other hand is valid only in countries that soeak American English Hence they have ranges of legitimacy or Scope The words in the left column could be considered global to British English in the sense that any average Brit would understand what was meant by each word and the words in the right column could be considered global to American English because everyone who speaks American English would associate each word with its intended meaning Enough of global scope now we need to talk about local scope Scope is local if it is a specific subset of some global scope For example the word neat has many different local scopes within the global American English language 1 Wow that movie was NEAT 2 Gertrude keeps the NEATest house I ve ever seen 3 Bartender l Il have my scotch NEAT In different situations neat can mean different things i e the meaning is local to the situation and these meanings don t overlap Variables in ACTION also have an associated scope A variable s scope determines where it may and may not be used just as in the above analogy a word s scope determines where it may and may not be used The following program is a concrete example of variable scope Example 1 MODULE we re going to declare some variables sas global CARD numgames 0 number of ganiee played goal 10 nurober of guesses to beat beatgoal 0 number of times you ve beaten goal PROC intro
46. the text block placed You may then paste the contents of the copy buffer the lines you wanted to move back into the program You can paste the text block at its original location and then move somewhere else and paste it there too thus enabling you to copy text blocks CURSOR MOVEMENT The cursor is controlled not only by the movement keys on the keyboard e g lt CTRl gt gt lt up arrow gt but can also be made to move to a specified places in your text through the use of tags and the FIND command TAGS You can mark any location in your text with an invisible marker called a tag The Editor allows you to move the cursor to this tag no matter where the cursor was before through the use of a simple command The number of tags you allowed is limited only to the number of keys on the keyboard since you must give a one character label to each tag you define Chapter 2 The Editor Commands This chapter is devoted to the Editor commands themselves Instead of presenting the commands in this form 2 2 lt CTRL gt lt SHIFT gt M where you can t tell what the section discusses unless you already know the Editor the commands are presented by their function e g 2 2 Leaving the Editor We hope this form makes things clearer and easier to follow Before going into the commands themselves we should tell you how to stop execution of a command if you made a mistake You can do this by pressing the lt ESC gt Key Doing t
47. the value you want put into the memory location specified by address When using PokeC the CARD value is stored in address and address 1 in LSB MSB order description These procedures allow you to change the contents of memory during program execution by changing the given address to the specified value 7 6 PROC Zero purpose to zero out a block of memory format PROC Zero BYTE POINTER address CARD size parameters address is a pointer to the starting address of the block you want zeroed size is the size of the block you want zeroed description With this procedure you can set all the values of the memory locations in a block to 0 This block starts at address and ends at location address size 1 7 7 PROC SetBlock purpose to set the memory locations of a memory block to a specified value format PROC SetBlock BYTE POINTER addr CARD size BYTE val parameters addr is a pointer to the starting address of the block you want to set size is the size of the block you want to set val is the value you want the bytes in the block set to description With this procedure you can set all the values of the memory locations in a block to val This block starts at addr and ends at location addr size 1 7 8 PROC MoveBlock purpose to move the contents of a block of memory format PROC MoveBlock BYTE POINTER dest source CARD size parameters dest is a po
48. to the Monitor The compiler takes over and does its job If it finds an error it will print out an error message and return you to the monitor If it finds no errors the Compiler will return us to the Monitor From there we can run the compiled program by entering the command RUN lt RETURN gt The screen should look like this after you ve run the program a EA gt 5 cana AR AREER ac Hello World E oe enc eae nae eae You have written your first ACTION program If you got an error message from the compiler it means that you didn t type the program in properly You can go back to the Editor from the Monitor by typing EDITOR and can fix your typo You might note that the cursor is placed at the position where the compiler found the error so you don t have to look all over for it Repeat the steps discussed above to re compile and re run your program after you ve fixed the error NOTES there is a list of the error codes with their meanings in appendix C Part Il The ACTION Editor Chapter Introduction 1 1 1 Special Notations 1 2 Editor Concepts and Features Chapter 2 The Editor Commands 2 1 Getting to the Editor 2 2 Leaving the Editor 2 3 Text Entry 2 3 1 Text File I O 2 3 2 Setting the Line Length 2 4 Cursor Movement 2 4 1 Tabs 2 4 2 Finding Text 2 5 Correcting Text 2 5 1 Deleting a Character 2 5 2 Inserting Changing a Character 2 5 3 Deleting
49. try it directly but as we mentioned above there are ways around over under and between the literal definition of the extended types The following example will fill an undimensioned array with a list of records The way it does this is simple once we define a virtual record because the array is actually a BYTE array with blocks of bytes being grouped into virtual records A virtual record is not a record in the sense that we declare It as a record type It is arecord only because we access a section of memory as though it were a record although it is really just a atring of bytes All we do is filla BYTE array so that it looks like contiguous records not bytes This is done by declaring a record data type and then declaring a pointer to that data type Then we manipulate the array in blocks the size of one record by making the pointer jump through the array in leaps the size in bytes of one record We will expand on this in the technical discussion following the example itself Example 1 MODULE declaring some global variables TYPE idinfo CARD idnum employee s I D number codenum his access code BYTE level his employment level BYTE ARRAY idarray 1000 enough space to hold 200 records DEFINE recordsize 5 CARD recount 0 PROC fillinfo This procedure will take some information on a given employee put it into an array of records using a pointer to the record type and Indexing that pointer in the ar
50. which fits into lt dest gt will be copied if lt dest gt is longer than lt source gt then SCopy will copy all of lt source gt into lt dest gt but not alter the rest of lt dest gt HINT don t dimension lt dest gt to avoid all the above problems 6 1 3 PROC SCopyS purpose to copy part of a string into another string format PROC SCopyS lt dest gt lt source gt BYTE start stop parameters lt dest gt is the identifier of the destination string CHAR ARRAY for the string copy lt source gt _ is the string with double quotes or identifier of the CHAR ARRAY used as the source string for the copy start is the starting point in lt source gt for the copy stop is the stopping point in lt source gt for the copy If stop is greater than the length of lt source gt it is changed to equal the length of lt source gt description This procedure will copy the elements of lt source gt from element start to element stop into lt dest gt In essence this works just like SCopy but copies only a part of lt source gt instead of the whole thing 6 1 4 PROC SAssign purpose to copy one string into part of another string format PROC SAssign lt dest gt lt source gt BYTE start stop parameters lt dest gt is the identifier of the destination string CHAR ARRAY for the string copy lt source gt _ is the string with double quotes or identifier of the CHAR ARRAY used as the source
51. working on two entirely different files without having to keep clearing window 1 and reading in a file NOTE the size of the window 1 can be set using the Options Menu available from the monitor For more information on how to do this see part III section 2 5 2 6 3 Moving Between Windows To move from window 1 to window 2 press lt CTRL gt lt SHIFT gt 2 If window 2 does not yet exist then the Editor creates window 2 then moves the cursor into it To move from window 2 to window 1 press lt CTRL gt lt SHIFT gt 1 2 6 4 Clearing a Window To clear the text file in a window move the cursor into that window see previous section and press lt SHIFT gt lt CLEAR gt Since this is such a powerful command the message area will prompt you with Clear Respond with a Y or N If you have made changes to the file viewed through that window and have not saved the changed version the message area will prompt you with Not saved Delete to make sure that you know that you have not saved the new version WARNING this command does not simply delete the portion of the file visible in the window but rather deletes the entire file 2 6 5 Deleting a Window To delete a window i e make the window itself go away first position the cursor in the desired window and then press lt CTRL gt lt SHIFT gt D In the message area you will see the prompt Delete Window Respond with a Y or N If you hav
52. you who already know all about parameters Parameters in PROC or FUNC declarations lt variable decl gt lt variable decl gt 1 where lt variable decl gt is a variable declaration except that it may not contain the lt addr gt or lt const gt option Examples PROC test BYTE Chr num i CARD x y INT FUNC docommand INT cmd CARD ptr BYTE offset CARD FUNC square BYTE t PROC jump Parameters in PROC or FUNC calls lt arith exp gt lt arith exp gt where lt arith exp gt is an arithmetic expression Examples Test cat dog ctr 2500 8D00 sqr square num jump x docommand temp var A NOTE A routine may have up to 8 parameters Use any more and you will get a compiler error We need to do some explaining now The following example will show you how to use parameters and clarify the first of the two advantages to using parameters The following function checks to see if the BYTE variable chr is a lowercase letter If it is the function will return the uppercase of it Otherwise the function will simply return chr Notice that we don t declare chr anywhere We ll discuss where it should be declared after the example BYTE FUNC lowertoupper IF chr gt a AND chr lt z THEN 20 is the offset RETURN chr 20 _ between lower and upper Fl case in the ATASCII set RETURN chr Now we must decide where to declare chr We already know that we coul
53. 2 to the given file name and call CIO to read buflen bytes DEFINE buflen 2000 length of the buffer array BYTE ARRAY fllename 30 the file name array buffer buflen the buffer array BYTE iocb2cmd 362 jlocb 2 s command byte CARD locb2buf 364 iocb 2 s buffer start address iocb2len 368 siocb 2 s buffer length PutE Print File name gt gt InputS filename get the filename Open 2 filename 4 0 open channel 2 for read only iocb2cmd 7 get binary record command iocb2buf buffer set iocb buffer to our buffer locb21en buflen set locb buffer length ClO 0 20 the call to ClO Close 2 closing channel 2 RETURN See how easy it is For those of you with an extensive set of assembly language routines this ability of ACTION allows you to use them in a high level language where building the framework of a program is easy 9 5 Advanced Use of Parameters In section 6 4 we discussed parameters and their usage mentioning that you couldn t pass a value out of a routine using a parameter Well that was a little white lie You can pass values out through parameters if you use pointers All you do is create a pointer which points to the variable you really want to pass into a routine and pass the pointer instead Then when you access what the pointer is pointing to you are really accessing the variable you wanted to pass You can then change the value of that variable using a
54. 5 SET directive syntax error 6 Declaration errorp You used the wrong declaration format when declaring something 7 Invalid argument list You gave a statement or routine too many arguments 8 Variable not declared Remember you must declare your variables before you use them 9 Not a constant You used a variable where a constant of some kind was required 10 Illegal assignment You are trying to do some sort of assignment that is not allowed e g var 5 gt 7 is illegal 11 Unknown error You have somehow impaired the ACTION system error routines so it can t tell you which error you have made 12 Missing THEN 13 Missing FI 14 Out of code space See Part V section 4 4 for more information 15 Missing DO 16 Missing TO 17 Bad Expression You have used an illegal expression format 18 Unmatched parentheses 19 Missing OD 20 Can t allocate memory You have impaired the ACTION system and it is uneble to allocate any more memory 21 Illegal array reference 22 The input file is too large You need to break it into smaller pieces 23 Illegal Conditional Expression 24 Illegal FOR statement syntax 25 Illegal EXIT There is no DO OD loop for the EXIT to exit out of 26 Nesting too deep 16 levels maximum 27 Illegal TYPE syntax 28 Illegal RETURN 61 Out of Symbol Table space See Part IV for more information 128 lt BREAK gt key was used to stop program execution Appendix
55. ARD number PROC PrintCE CARD number PROC PrintCD CARD channel number PROC PrintCDE CARD channel number parameters number is an arithmetic expression remember that arithmetic expressions can simply be a constant or variable name channel is a valid channel number 0 7 description The above procedures output CARDs as follows PrintC outputs the CARD to the default channel without a lt RETURN gt at the end PrintCE outputs the CARD to the default channel with a lt RETURN3 gt at the end PrintCD outputs the CARD to a specified channel without a lt RETURN gt at the end PrintOCDE outputs the CARD to a specified channel with a lt RETURN3 gt at the end 2 1 4 Printing INT Numbers purpose to output numbers as INTs in decimal format formats PROC Printl INT number PROC PrintlE INT number PROC PrintID INT channel number PROC PrintIDE INT cbarinel number parameters number is an arithmetle expression remember that arithmetic expressions can simply be a constant or variable name channel is a valid channel number 0 7 description The above procedures output INTs as follows Printl outputs the INT to the default channel without a lt RETURN3 gt at the end PrintlE outputs the INT to the default channel with a lt RETURN gt at the end PrintID outputs the INT to a specified channel without a lt RETIfRN gt at the end PrintIDE outputs the INT to a specified channel with a lt RETURN gt a
56. Atari system with the standard display EOL character blank E The EOL End Of Line character is the character displayed by the ACTION editor at the end of a line Enter the character which you want to see displayed as the visible EOL character then press lt RETURN gt Changing from a space to a visible character would generally only be useful for removing trailing spaces from lines However you may prefer a visible EOL for reasons of your own lf you desire such we suggest any of the Atari graphics characters e g lt CTRL gt T is a solid circle 2 6 PROCEED Restarting a Halted Program Restart a halted program continue from a stop caused by pressing the lt BREAK gt key using the Break Library routine by entering PROCEED then pressing lt RETURN gt The program continues as if the interruption had not occurred Examples PROCEED lt RETURN gt P lt RETURN gt 2 7 RUN Program Execution You can run any program which has just been compiled and is still In the program area The command has the following formats RUN RUN lt filespec gt RUN lt address gt RUN lt routine gt where lt routine gt ia a valid PROC or FUNC identifier e g for PROC Prime you would use Prime as the routine identifier The first format is used to run a program you have compiled from the Editor buffer The second allows you to run programs stored on peripheral devices Ifthe program is still in the ACTI
57. C and RETURN statements are required by the ACTION language and make up the bones of a procedure The language is structured into a group of subroutines called procedures and functions with each routine doing a specific task which you define This might seem strange at first but it allows you to write programs in components so that you can concentrate on one part of the program at a time It also makes programs written by others much easier to read The above procedure is called hello namely because it will print out the line Hello World to the screen when the program is run The statement starting with PrintE is a library routine call Here we are making use of one of the prewritten routines in the ACTION library This one will print out the specified string and put outa lt RETURN gt at the end This routine call is the only statement in the procedure hello because it is the only statement between the PROC and RETURN Now that we have the program in the Editor buffer how are we going to compile and run it The Editor certainly can t do it for us so we need to get to the Monitor and call the ACTION Compiler from there The Editor command lt CTRL gt lt SHIFT gt M takes us to the Monitor so we ll use that Now that we re in the Monitor we need to call the Compiler to check the syntax of our program and translate it into machine language This is done by typing the command COMPILE lt RETURNs gt
58. D Bibliography and References D 1 Atari 400 800 Hardware Systeins Atari Publications ATARI Personal Computer System Operating System User s Manual and Hardware Manual ATARI 810 Disk Drive Operator s Manual ATARI 400 800 Disk Utility ATARI 400 800 Operating Systems ATARI 400 800 Disk Operating Systems II Reference Manual Other Atari References Poole McNiff Cook Yoor Atari Computer D 2 Optimized Systems Software References OSS OS A reference manual OSS DOS XL reference manual Appendix E Editor Commands Summary E 1 1 O Commands Read A File position cursor lt CTRL gt lt SKIFT gt R enter file spec Disk Directory lt CTRLi lt SHIPT gt R n n is the device name Write a File lt CTBL gt lt SHIFT gt W enter fllespec List to Printer lt CTRL gt lt SHIPT gt W enter P E 2 Cursor Movement within Window Up lt CTRL gt lt up arrow gt Down lt CTRL gt lt down arrow gt Right lt CTRL gt lt right arrow gt Left lt CTRL gt lt left arrow gt Start of Line lt CTRL gt lt SHIPT gt lt End of Line lt CTRL gt lt SHIFT gt gt Next Line lt RETI RN gt Tab lt TAB gt E 3 Tab Handling Set Tab lt SHIFT gt lt SET TAB gt Clear Tab lt CTRL gt lt CLR TAB gt E 4 WiIndcmr Movement Start of File lt CTRL gt lt SHIFT gt H Up one screen lt CTRL gt lt SHIFT gt lt up arrow gt Down on
59. DITOR Many advanced features for easily creating and modifying source text two separate program windows each al lowing up to 240 characters per line fast horizontal and vertical scrolling move and copy text string find and replace and much more THE MONITOR Selects compilation options saves compiled programs examines variable values and memory locations and even traces the execution of your programs THE COMPILER Super fast compilation into machine code accepting source from the Editor or from tape or disk THE LIBRARY A built in collection of useful subroutines for you to use in your programs including string manipulation print procedures and formatting 1 O routines and graphics and game controller routines
60. Examples chr lowertoupper chr cat lowertoupper cat var lowertoupper a Making chr a parameter to the function allows you to use it for testing any variable in any program because lowertoupper now stands on its own It uses no variables declared elsewhere i e global variables and yet you can give it a variable to test We have overcome the pitfalls of declaring chr either locally or globally Tah dahl This is what we meant by multipurpose The second advantage to using parameters is more difficult to illustrate but we re going to make it as clear as possible again by using an example The following procedure takes two CARD type numbers divides the first by the second and prints out the result PROC division CARD num div num div changes num to num div PrintC nun print out num RETURN And now to use the division procedure in a program Example 1 PROC main CARD ctr nuirber 7 13 FOR ctr 1 TO 10 DO Pr i ntC number Print PrintC ctr Print division number ctr PutE OD RETURN Output 1 713 1 713 713 2 356 713 3 237 713 4 178 713 5 142 713 6 118 713 7 101 713 8 89 713 9 79 713 10 71 Notice that number remains constant although num changes The value of number is passed into num when the procedure is called but the value of num is not passed back into number when the procedure is exited If the value of nun w
61. Library and it enables you to do all the things you can do in BASIC i e PLOT DRAWTO PRINT etc and much more without writing any special subroutines of your own TECHNICAL NOTE although the ACTION compiler does translate an ACTION program to 6502 machine language that compiled code will not run without the ACTION cartridge because it the code does some calls to routines in the cartridge If you are writing products for resale a runtime version of ACTION which will make your program work without the cartridge can be licensed from OSS Inc Chapter 2 How To Write and Run an ACTION Program This chapter is designed to let you get your feet wet and become more familiar with the ACTION System We re going to write a little program in the Editor Compile that program and Run it When you go to the cartridge from DOS you will be in the ACTION Editor so the program can be entered immediately We re going to assume that you won t make any typos but if you do you can use the cursor control keys lt CTRL gt lt up arrows etc to move around and fix them When you read the Editor part you will find out about many more editor features and commands but these are all you need for this program Now let s look at the program Enter it exactly as you see it here no special commands are required to enter text PROC hello PrintE HelLo Worl RETURN Before we compile this program let s discuss what s going on The PRO
62. ON language it is first compiled by the Compiler and then it is run If it is in machine code i e you saved the compiled version of your program using the WRITE Monitor command the program runs immediately The third format allows you to run a program or routine which begins at a given address This is useful when you are trying to debug a program which calls a machine language routine you have written The fourth is used to run only one routine from a program which you have compiled After program execution control returns to the ACTION monitor When some kind of significant error occurs e g an infinite loop control does not return to the ACTION Monitor Such an error requires pressing the lt SYSTEM RESET gt key in order to return to the ACTION monitor Additional information on the behavior of running programs is in the next chapter Examples RUN lt RETURN3 gt run a program compiled R lt RETURN gt from the Editor buffer RUN C lt RETURN gt pull a program from cassette compile it then run it RUN PRIME ACT lt RETURN gt pull PRIME ACT from R D1 PRIME ACT lt RETURN gt disk 1 compile it then run it R 400 lt RETURN gt run a program at addre amp s 400 RUN 1024 lt RETURN gt run a program at address 1024 R Prime lt RETURNs run the just compiled procedure Prime RUN PrintE lt RETURN gt run the library function to print a string to the screen 2 8 SET Setti
63. Put Print and Input routines also use these registers as references for the current cursor location so you can use this to move to any position and then use another routine to manipulate what s there The first thing you see is the section number and name of the routine including what type of routine it is in this case a BYTE FUNCtion This is followed by a short description of the purpose of the routine The format of the routine itself is then given in the form of a routine declaration The declaration form is used instead of the form used to call that routine because it tells you more information about the routine in question including 1 the routine s type PROC or FUNC 2 all the parameters 3 the data type of each parameter After the format of the routine is given the parameters required by that routine are explained one by one The last piece of information is a description which discusses the use of the routine in general and its performance in certain special conditions Chapter 2 Output Routines The ACTION Library provides an extremely extensive group of routines to put both numeric and string data out to any channel The two basic output routines Print and Put have options which allow you to direct the output to a specific channel and or output an EOL End of Line a k a lt RETURNS gt following the data We ll go into these options in more detail in the following sections 2 1 The Print Procedures The pro
64. RD INT No Options Print PrintB PrintC Printl With EOL PrintE PrintBE PrintCE PrintlE To Device PrintD PrintBD PrintCD PrintlID Both Options PrintDE PrintBDE PrintCDE PrintIDE Notice that we have grouped the procedures according to the type of data which they output This is the way in which we group them in the following sections with each section giving the purpose format parameters and discussion for each option of the Print procedure basic to that type of data There is one Print procedure not in the above list because it is a very special case as far as output is concerned Its name is PrintF and it allows you to format output which contains numbers and strings A separate section is devoted to this routine alone 2 1 1 Printing Strings There are four string printing procedures thus making all the options discussed in the previous section available purpose to print out a string uajng some format options formats PROC Print lt string gt PROC PrintE lt string gt PROC PrintD BYTE channel lt string gt PROC PrintDE BYTE channel lt string gt parameters lt string gt is either a string constant with double quotes or the identifier of a BYTE ARRAY which you want printed out as a string channel is a valid channel number 0 7 descriptions These four procedures print out strings thus Print outputs the string to the default channel without a lt RETURN gt at the end PrintE outputs the
65. S 2S Example 5 39 00000101 5 00100111 39 00100111 result of is 39 Table 3 Bit Wise XOR returns a value Bit A Bit B Result based on this 0 0 0 table 0 1 1 1 0 1 1 1 0 Example 5 39 00000101 5 00100111 39 00100010 result of 1 is 34 Both LSH and RSH shift bits If they operate on two byte types CARD and INT the shift occurs through both bytes In the case of INT the sign of the number is not preserved when using RSH or LSH and may change Their form is lt operand gt lt operator gt lt number of shifts gt Where lt operand gt Is a numeric constant or variable lt operator gt Is either LSH or RSH Is a numeric constant or a variable that is used to determine the number of bits to shift the operand by lt number of shifts gt Some examples to illustrate both LSH and RSH follow Table 4 8 bit shift operations 5 00000101 39 00100111 5 LSH 1 10 00001010 39 LSH 1 78 01001110 5 RSH 1 2 00000010 39 RSH 1 19 00010011 Table 5 16 Bit Shift Operations Operation MSB LSB Description 01010110 11001010 56CA LSH 1 10101101 10010100 56CA LSH 1 AD94 RSH 1 00101011 01100101 56CA RSH 1 2B65 LSH 2 01011011 00101000 56CA LSH 2 5B28 RSH2 00010101 10110010 56CA RSH 2 15B2 Notice that a LSH b
66. SHIFT gt U Undo text changes This command restores a changed line to its unmodified state Tags for that line are not restored This command works only ona line not deleted by lt SHIFT gt lt DELETE gt and while the cursor has not left that line lt CTRL gt lt SHIFT gt W This command Writes a file to a peripheral storage device The file name must be compatible with the DOS you are using lt CTRL gt lt SHIFT gt This command Moves the window right 1 column useful for editing files with lots of indentation lt CTRL gt lt SHIFT gt This command Moves window to the left 1 column lt CTRL gt lt SHIFT gt lt up arrow gt This command Moves the current window up a complete window For continuity between the old and new windows the top line from the last window is the new window s bottom line lt CTRL gt lt SHIFT gt lt down arrow gt Moves the current window down 1 window The new window s top line is pulled from the previous window s bottom line lt CTRL gt lt SHIFT gt 1 This command Moves from the second window to the first window The cursor goes to the previous cursor position if any lt CTRL gt lt SHIFT gt 2 This command Moves from the first window to the second window If the second window has not been created previously in the current editing session then the second window is created on the screen The editor goes to the previous cursor position if any lt CTRL gt lt SHIFT gt gt Moves
67. ST compiler As with TRACE above this variable must be used in a SET directive and it must come at the beginning of your program A 0 turns the listing off and a 1 turns it on 7 12 BYTE ARRAY EOF 8 With this library variable you can find out if you ve reached the End Of File on any channel Simply give the number of the channel as the subscript to the EOF array For example if you wanted to find out if you have reached the End of File on channel 1 the channel must be open then you would use IF EOF 1 THEN do something here FI EOF equals 1 when the End Of File has been reached otherwise it is 0 Appendix A ACTION Language Syntax Retyped in by Jim Patchell on February 13 2010 It should be noted that I have made some additions to and correction to this BNF grammar I added in the assign ops and also fixed the complex rel production Maybe they were correct in the original but I have a hard time reading these days Anyway the grammar seems to more or less work this way The following is the syntax of the ACTION Language in Backus Naur form BNF This form has a couple of special characters Symbol Meaning is defined as LPE or optional The appendix is set up to allow you easy access to the particular information you want with subsections as follows A 1 ACTION Constants Numeric Constant String Constant Compiler Constnat A 2 Operators and Fundamental Data Types Operators Fu
68. TURN end of program All you are really doing is changing the pointer to the system error routine so that it points to your error routine instead You don t have to call this routine because it will be called by the ACTION system when an error is encountered Notice that we saved the original error routine pointer and then at the end of the program we reset that pointer which was changed to point to your error routine back to the system error routine This was done so that the system could again use its error routine after your program finished running WARNING the capability of substituting your error routine for the system s should be used very carefully because you might forget to check for something in you routine and thereby cause the entire system to crash 7 4 BYTE FUNC Peek and CARD FUNC PeekC purpose to return the value BYTE or CARD at a given memory location format BYTE FUNC Peek CARD address CARD FUNC PeekC CARD address parameters address is the address of the memory location you desire to look at description These two functions allow you to look at memory during program execution either as a BYTE or a CARD In LSB MSB order 7 5 PROC Poke and PROC PokeC purpose to insert new values BYTE or CARD into a specified memory location format PROC Poke CARD address BYTE value PROC PokeC CARD address value parameters address is the address of the memory location you desire to change value is
69. a blank line on the line where the cursor is The line where the cursor was and succeeding text lines are moved down to make room for this line lt CTRL gt lt INSERT gt Inserts a blank space where the cursor is Succeeding characters on the same line are moved right one character to make room for the inserted space lt CTRL gt lt up arrow gt Moves cursor up one text line lt CTRL gt lt down arrow gt Moves cursor down one text line lt TAB gt Move to the next set TAB location if any Do not move if no additional TAB exists Inserts spaces if no text or spaces exist here already lt SHIFT gt lt SET TAB gt Establish a TAB location at the current position of the cursor lt CTRL gt lt CLR TAB gt Clear the TAB if any at the current cursor location 3 2 Differing Commands lt BREAK gt This key is not used by the ACTION editor lt SHIFT gt lt CLEAR gt Clears file in the current window The editor warns you when the file has not been saved since the last text modification and allows you to cancel the command lt RETURN gt In Replace mode this moves the cursor to the beginning of the next line In Insert mode it inserts a lt RETURNs gt into the text lt SHIFT gt lt DELETE gt Removes the line the cursor is on like Atari screen editor Succeeding lines are moved up to replace the deleted line Can be used repeatedly Removed line s is are stored in a temporary holding area called the c
70. a device with your file name the compiler assumes the device is D1 You can INCLUDE files from any readable device i e P isn t valid Here are some more examples INCLUDE D2 IOLIB ACT INCLUDE PROG DAT INCLUDE C NOTE Most operating systems require that the file specifiers be in uppercase A useful feature of the INCLUDE command is that you can have an INCLUDE in a program which you are already INCLUDEing i e it can be nested ACTION Allows you to nest it to a maximum of 6 levels but peripheral devices and the operating system have other limits When the OS limits are ignored error 161 too many files open occurs The cassette limit is 1 INCLUDE and the disk drive limit Is 3 INCLUDES If no program is currently in the ACTION editor buffer then the maximam number of levels of INCLUDE commands is reduced by one 7 3 SET The SET directive is used to modify the computer s RAM Random Access Memory SET pokes a new value into a specified memory location at compile time In most cases this command is used for changing Editor and Compiler options from a user program but it can be used to modify user operating system and hardware variables as well The format of the SET command is SET lt address gt lt value gt NOTE lt address gt and lt value gt must be compiler constants The result of the set statement is to set memory location lt address gt to lt value gt If lt value gt is greater th
71. a long program which includes routines from other sources remember the INCLUDE command If this is so then you might never be able to get the source code together for a complete listing otherwise You can get such a listing and even redirect it to the printer See part VI section 7 9 To enable the listing press Y lt RETURNs gt to the List options menu prompts Chapter 4 Technical Considerations 4 1 Overflow and Underflow The ACTION Compiler does no checks for mathematical overflow or underflow What is overflow and underflow anyway They are opposite sides of the same coin If you have a BYTE variable which currently equals 255 and you add 1 to it you won t get 256 because a single byte can only contain values up to 255 you ll get 0 Similarly if you are using the decimal system and only have two digits of display you can run into the same problem if you add 1 to 99 You know that it equals 100 but you only have two digits of display so you see 00 Underflow is the exact opposite of this If you subtract 1 from 0 you get 255 As mentioned in part IV section 4 2 some of the mathematic operators result in a specified type of output so you can sometimes avoid the above problems by making use of these automatic type changes Likewise shift operations can cause overflow and underflow A shift of the contents of a variable produces similar but not identical results to those achieved by multiplying
72. a simple matter to execute them It s very similar to a list of Chores such as 1 Make your bed 2 Clean your room 3 Dust the living room furniture 4 Wash the Dog except that the computer will do the tasks in the order in which you present them not in whatever order it likes best Having separate components also makes it very easy for you to do a single task over and over or do the same task in ten different situations and places The only requirement this structured approach imposes is that a program must consist of proper components in ACTION they are called procedures and functions for It to be valid A program usually contains many components but at least one is required This is not a restrictive requirement at all as you will soon find out In fact it makes your program more comprehensible to yourself and others NOTE when compiling and running a program with many routines the last routine is considered to be the main one so you should use it to control your program Chapter 2 ACTION Vocabulary In our discussion of ACTION we will use some terminology that we should explain We ll use as little jargon as possible but some is required to differentiate between parallel but different concepts later on What terms we don t present here will be explained when they are first used Before going into the special notations used in this part we ll give you a list of the keywords in ACTION A keyword is any word or sy
73. able of data type rec brec 8000 Declares brec to be a variable of data type rec and places it at memory location 8000 So now that you know how to declare a record data type and then declare variables of that type it s time to find out how to reference and manipulate records 8 3 2 Record Manipulation To learn how to manipulate records we first must learn how to reference a field within a record The following program does just that using the period operator We ll discuss its usage after the program itself Example 1 PROC recordreference This procedure reads in some information about an employee and then prints it out to let the employee know it s correct TYPE idinfo BYTE level employee s level CARD idnum his 1 D number entry_year year he started idinfo rec declaring rec as record type idinfo Print What is your I D number rec idnum InputC get his I D number Print What is your employment level A Z rec level GetD 7 get his employment level Print In what year did you start working here rec entry_year InputC get his entry year PrintE O K Here s what have PutE Print I D PrintCE rec idnum Print Print Level out the Put rec level information PutE the employee Print Entry year entered PrintCE rec entry_year ef RETURN end of PROC recordreference Output 1 What is your I D
74. accomplish the task 2 an accepted order in which these actions are done Drying the dishes before you wash them breaks the accepted order and taking off your left sock is not an action related to Doing the dishes We know these things from experience and have lumped the proper group of actions done in the proper order into a procedure one which we call Doing the dishes In computer languages it s the same way You make a group of actions that accomplish a single large task into a procedure or function which you then give aname When you want to execute this task all you do is use the procedure or function name with some extras we ll discuss later This is referred to as a procedure or function call The procedure or function must have already been defined just like in English e g you wouldn t know what to do if someone told you to readjust the widget unless you already knew the actions required to do this Now what is the difference between procedures and functions They both go through a series of ordered steps to accomplish a task so why two names for the same construct That is because they re not exactly the same construct Functions have an added property they do their task and then return a value In the table at this section s beginning we see mBalancing your checkbook given as a function example Why Well when you balance your checkbook you go through a series of steps to bring your records up to date and come u
75. ady talked about the first format but the other three require some explanation When you use a predefined identifier i e a variable procedure or function name in a compiler constant the value used is the address of that identifier The third format allows pointer references as compiler constants The last one permits you do simple addition of a combination of any two of the other three types Here are some examples which show the valid formats in use cat uses the address of the variable cat 6000 a hex constant dog a pointer reference as a constant 5 ptr 5 plus the contents of the pointer ptr 80 p evaluates to 80 plus the address of p 3 3 Fundamental Data Types Data types allow humans to make sense out of the stream of bits the computer understands and manipulates They allow us to use concepts we understand so we need not know how the computer does what it does ACTION supports three fundamental types and some advanced extensions of these see chapter 8 for the extended types The basic ones are BYTE CARD and INT and each is detailed below All of the fundamental types are numeric and so allow you to use numeric format when entering data 3 3 1 BYTE The type BYTE is used for positive integers less than 256 It is internally represented as a one byte unsigned number its values range between 0 and 255 At first glance this might seem a useless type but it has two worth while applications When used a
76. al storage device Disk Drive Cassette etc to save you all this trouble To save a program in the Editor buffer you must first put the cursor into the window which contains the file you want saved if you are using only one window you needn t worry about this Then you enter the command lt CTRL gt lt SHIFT gt W In the message area you will see Write Simply type in the file name you want the program saved to and press lt RETURN gt _ The file name must be compatible with the DOS you are using If you are not using a DOS the file will consist only of a character representing the device C for cassette P for printer etc followed by a colon Reading a file into the Editor buffer is just as easy Move the cursor to the line preceding the line where you want the file you re reading in to start and enter the command lt CTRL gt lt SHIFT gt R In the message area you will see Read Type in the name of the file you want read in following the conventions outlined above If you are using floppy disks you can read the directory on a given disk by replying with the following to the Read prompt in the message area Read 1 This will read the directory of the disk in drive number 1 If you want to read the directory of a disk in some other drive simply change the 1 in the above example to the number of the drive This ability is very useful because you needn t go to DOS to find out what is on a disk 2 3
77. am itself PROC doerror BYTE errnum This procedure reads in the error number and sprints out the related message See the discussion following the program for an explanation of how it works BYTE ARRAY errmsg the message printed out CARD ARRAY adadr 6 sholds the addresses of the error medsages addr 0 Illegal commana addr 1 Illegal character See addr 2 Bad File Name Example 4 addr 3 Number Too Large Note for an addr 4 Wrong Type Of Number explanation addr 5 Unknown Error errmsg addr errnum puts the error message asso lt Print ERROR ciated with errnum in PrintB errnum errmsg and prints it Print out after the error num PrintE errmsg ber itself PutE RETURN End of procedure doerror PROC main This procedure is just a dummy used to call the above procedure using all valid error numbers to show that the table works BYTE error FOR error 0 TO 5 DO doerror error OD RETURN End of procedure main Output 14 ERROR 0 Illegal command ERROR 1 Illegal character ERROR 2 Bad File Name ERROR 3 Number Too Large ERROR 4 Wrong Type Of Number ERROR 5 Unknown Error EXAMPLE 4 NOTES The way in which we fill the CARD array in this example is strange how can you fill a CARD array element with a string but is perfectly valid because the string constant itself is not being assigned to the array element rather Its address is This mak
78. an 255 then memory locations lt address gt and lt address gt 1 are assigned lt value gt This occurs because 255 FF is the biggest decimal number that can fit into one byte so any number greater than this requires two bytes for storage Examples SET 600 64 sets address 600 equal to 64 SET max 16 sets max 16 SET 10000 FFFF sets 10000 and 10001 to FFFF SET CF00 cat sets CFOO and CFO1 cat DEFINE add 7000 SET add 42 The last example shows a DEFINEd numeric constant used in a SET statement Since DEFINES are constants at compile time they are valid in the SET directive Just make sure you DEFINE the constant before you use it in a SET statement NOTE do not confuse the compile time effect of SET with the similar run time effect of Poke and PokeC Chapter 8 Extended Data Types The extended data types make the ACTION language more flexible than many others available on the ATARI Just as the structured statements manipulate groups of simple statements thereby extending the capabilities of the ACTION language the extended types manipulate groups of fundamental type variables and extend the language capabilities even more The three extended data types in ACTION are 1 Pointers 2 Arrays 3 Records We will discuss each separately following the order of the above list 8 1 POINTERS Pointer Sounds like the thing the weatherman uses to show us a place on his map Well itis Inthe context of ACTION
79. ariables lt statement list gt is the list of statements in the function RETURN denotes the end of the function lt arith exp gt is the value you wish returned from the function As in procedure declarations lt parameter list gt lt variable decl gt and lt statement list gt are all optional In the case of procedures leaving them out was useful only in one instance In functions doing this sort of thing has another more worthwhile use as the following example shows Example fit CARD FUtNC square CARD x RETURN x x This function takes a CARD number and returns its square Don t worry about the parameter list as we will discuss it a little later It was mentioned above that the value returned is in the form of an arithmetic expression In example 1 you can see this being done in x x In the following example the arithmetic expression used to return a value is simply a variable name Example 2 BYTE FUNC getcommand This function reads in a command number and then passes it out if it s 1 through 7 inclusive Otherwise the function will reprompt the user BYTE command this variable holds the command error set to 1 If an error is found DO Print COMMAND gt Cominand InputB IF command lt 1 OR commands7 THEN invalid command Error 1 PrintE Command Error Only 1 7 valid ELSE valid command Error 0 Fl UNTIL error 0 exit loop if command is valid OD RETUEIN
80. at expression and simplified exp shows the expression after the evaluation has taken place Notice that expressions 2 through 4 contain another expression as one of their operands but that this expression as an operand has already been evaluated leaving a number in its place as seen in simplified exp Some examples follow all lowercase words are variables or constants Expression Evaluation order A dog 7 3 564 None Var amp 7 MOD 3 MOD amp Ptr xyz Arithmetic expressions in ACTION may involve operands of differing data types The result of such mixing is outlined in the table below The type at the intersection of any row and column is the type resulting when the row s and column s types are mixed BYTE INT CARD NOTE using the unary minus BYTE BYTE INT CARD negative sign results in an INT INT INT CARD Implied INT type and using the CARD CARD CARD CARD address operator results in an implied CARD type TECHNICAL NOTE using the operand results in an INT type so multiplication of very large CARD values gt 32767 will not work properly 4 3 Simple Relational Expressions Relational expressions are used in conditional statements to perform tests to see whether a statement should be executed more on conditional statements in section 5 2 1 Note that they may be used ONLY in conditional statement
81. atements in ACTION 1 Assignment Statement including FUNCtion Calls 2 PROCedure Calls PROCedure and FUNCtion calls are discussed in chapter 6 and the assignment statement follows There are two keywords that are also simple statements EXIT section 5 3 3 2 RETURN sections 6 1 2 and 6 2 2 but the last two are used in specific constructs and so are discussed where appropriate to their usage 5 1 1 Assignment Statement The assignment statement is used to give a value to a variable Its most common form is lt variable gt lt arithmetic expression gt NOTE lt variable gt may be a variable of a fundamental data type or it can be an array pointer or record reference NOTE the expression MUST be arithmetic If you try to use a relational expression you will get an error because the ACTION compiler does not assign a numerical value to the evaluation of a relational expression The assignment operator is It tells the computer that you want to assign a new value to the given variable Do not confuse it with the relational Although they are the same character the compiler reads them differently each according to its context The following examples illustrate the assignment statement You ll notice a variable declaration section preceding the examples themselves It s there because some of the examples show what happens when you mix types i e the variable and value being assigned to it are not of t
82. ay of records using the same format in which the array was filled otherwise some strange problems will arise Before we go on to show the program that looks into the filled array let s first modify the records a little bit We ll add one more field which will contain the employee s name in the form Las Name First Name To do this we must somehow make the field an array Or must we Instead let s simply add a BYTE field to the end of the record type and then change the DEFINE directive to make the size given each record increase If we increase it by 20 suddenly we have 25 bytes reserved for 6 bytes of field 2 CARDs and 2 BYTEs Then we just put the string in the extra space by accessing the last field our new BYTE field and putting in a string instead of abyte The string can t be longer than 19 characters recall the first byte of a string is its length so we ll have to make sure the string is short enough Without further ado we ll move onto the extended version of the idinfo procedure complete with strings Example 2 MODULE declaring some global variables TYPE idinfo CARD idnum employee a I D number codenum _ his access code BYTE level his employment level name first letter of name BYTE ARRAY idarray 1000 enough space to hold 40 records DEFINE recordsize 25 nameoffset 5 CARD reccount 0 PROC fillinfo This is simply the modified version of the Previous example idinfo POINTER
83. ayed depends on the graphics mode and the color of the point depends on the current value of the library variable Color see previous section 5 5 PROC DrawTo purpose must be preoeeded by a Plot to draw a line between the point just Plotted and the specified position format PROC DrawTo CARD col BYTE row parameters col is the horizontal column number of the end point of the line row is the vertical row number of the end point of the line description This procedure is used in graphics modes 3 8 to draw a line from the point just plotted using Plot and the position given by the parameters The color of the line depends on the current value of the library variable Color see section 5 3 5 6 PROC Fill purpose must be preceded by a Plot fills a box with a color format PROC Fill CARD col BYTE row parameters col is the horizontal column number of the lower right corner of the box being filled row isthe vertical row number of the lower right corner of the box being filled description This Allows you to make boxes of color in graphics modes 3 8 The upper left corner of the box is defined by the position of the Plot immediately before the Fill and the lower right corner is given by the parameters The color used is decided by the contents of the library variable Color 5 7 PROC Position purpose to position the cursor anywhere on the screen format PROC Position CARD col
84. cedures we are about to discuss all have one thing in common they begin with the word Print From this alone you can tell that they print something out somewhere but who knows what and where The answers to these questions can be found by looking at the option s tagged onto the end of the word Print These options all consist of a single letter but you can employ up to three options at one time because different options control different aspects of the output Is this ever confusing it might seem that way but let s look at the format of Print to see how these options are grouped Print lt data type gt d e lt parameters gt where Print is the basic function name lt data type gt tells what type of data you want to output The options here are B BYTE type data C CARD type data INT type data lt nothing gt a string D stands for device and is used when you want to define which device channel you want the output to go to E stands for EOL End Of Line and is used to ouput a lt RETURN gt after the data lt parameters gt are the parameters required by the procedure and range in number NOTE Both the D and E are optional but a data type is always specified because a string is assumed to be the type of data output if no type is explicitly given From the above format you can see that the following are all the possible Print routines string BYTE CA
85. code_num THEN a match nameptr recptr nameoffset Print l D PrintCE recptr idnum Print Levels Put recptr level Print Name PrintE nameptr PutE PrintE OK TO PASS ELSE code does not match PrintE DO NOT PASS Fl end of access code testing FI end of D number verification Fl end of keyld check OD end of infinite loop FI end of IF mode A PrintE System Shutdown RETURN end of PROC main All the main procedure does is go through a series of checks to determine what needs to be done at any given point The nested IFs are somewhat confusing but they are lined up that is indented the same amount so you can do IF FI paring by placing a ruler vertically on the page and sliding it back and forth to change levels of nesting Chapter 9 Advanced Concepts This chapter deals with some techniques the experienced programmer might find useful Thus far we have limited our discussion of the ACTION language to a study of the language with respect to itself that is without reference to the rest of the computer Most of this chapter is devoted to interfacing ACTION to information external to ACTION itself including operating system routines and system variables 9 1 Code Blocks Code blocks allow you to include machine code in your program When the compiler sees a code block it will put the values in the block into the code generated just as though it were code generated by the compiler No
86. const gt lt base comp const gt lt comp const gt lt base comp const gt lt base comp const gt lt identifier gt lt num const gt lt ptr ref gt A 2 Operators and Fundamental Data types Operators lt special op gt AND OR amp lt rel op gt XOR I T P S L H gt lt 1 lt gt gt lt lt add op gt lt mul op gt MOD I LSH RSH lt unary op gt Fundamental Data Types lt fund type gt CARD CHAR BYTE INT A 3 ACTION Program Structure lt program gt lt program gt MODULE lt prog module gt lt MODULE lt prog module gt lt prog module gt lt system decls gt lt routine list gt A 4 Declarations System Declarations lt system decls gt lt system decl gt lt system decls gt lt system decl gt lt system decl gt lt DEFINE decl gt lt TYPE decl gt lt fund decl gt lt POINTER decl gt lt ARRAY decl gt lt record decl gt DEFINE Directive lt DEFINE decl gt DEFINE lt def list gt lt def list gt lt def gt lt def list gt lt def gt lt def gt lt identifier gt lt constant gt TYPE Declaration for records lt TYPE decl gt TYPE lt rec ident list gt lt rec ident list gt lt rec ident list gt lt rec ident gt lt rec ident gt lt rec ident gt lt rec name gt lt field init gt l
87. cription This procedure closes the specified channel At the end of a program you should always close any devices that you have opened in the course of that program NOTE DO NOT Close channel 7 as ACTION uses it 4 3 PROC XIO purpose provides access to the device specific commands For example to change the baud rate on an RS232 device you would make a call to the XIO handler for the R device to do this format PROC XIO BYTE chan 0 cmd aux1 aux2 lt filestring gt parameters chan is a valid channel number 0 7 cmd is the equivalent of the IOCB COMMAND byte ICCOM in OS A and DOS XL aux1 is the first auxiliary byte in the IOCB ICAUX1 in OS A and DOS XL axu2 is the second auxiliary byte in the IOCB ICAUX2 in OS A and DOS XL lt filestring gt is a character string specifying a standard device with a file name in the case of D description This procedure is a system call designed to provide access to DOS Those of you familiar with Atari Basic BASIC A or BASIC XL will recognize XIO as a direct translation of BASIC s XIO statement Rather than give a complete list of all the possible uses of XIO here we will refer you to chapter 8 of either the OS A or DOS XL manual The ACTION XIO procedure can perform all the system commands listed therein other than NOTE POINT and the various data transfer operations all of which are available via other ACTION library routines 4 4 PROC Note purpose t
88. d declare it global or just local to lowertoupper If we declare it locally how will we give ita value There seems to be no use to having it local because then the function itself would have to give the variable a value and that s not what we want the function to do We want to be able to call lowertoupper in a form similar to chr lowertoupper and have the function test chr and make It uppercase if necessary So we won t declare it local How about declaring it global That would do what we wanted because now the chr in the function call and the chr in the function itself would be the same global variable There s only one drawback to declaring chr as a global variable every time we wanted to use lowertoupper we would get the uppercase of chr If we want to uppercase the variable cat we would have to do the following chr cat chr lowertoupper cat chr This could get very tiresome if you wanted to uppercase a lot of different variables Also if you wanted to use lowertoupper in another program you would have to declare a global variable chr there too What if we declared chr as a parameter to the function HOW you ask Here s how BYTE FUNC lowertoupper BYTE chr lt the parameter declaration IF chr gt a AND chr lt z THEN RETURN chr 20 FI RETURN chr But now how do we call it now Easy All you have to do is give it the variable you want tested as a parameter
89. d substring insertion There is one caution however and that is remember that the maximum length of a string is 255 characters so don t try to use these routines to create or to manipulate big CHARacter arrays 6 1 1 INT FUNC SCompare purpose to compare alphabetically two strings format INT FUNC SCompare lt string1 gt lt string2 gt parameters lt string1 gt is a string with double quotes or the identifier of a CHAR ARRAY which is a string lt string2 gt is a string with double quotes or the identifier of a CHAR ARRAY which is a string description This function returns a value dependent on the following tables comparison value returned lt string1 gt lt lt string2 gt value lt 0 lt string1 gt lt string2 gt value 0 lt string1 gt gt lt string2 gt value gt 0 The comparison is alphabetic so this is a good way to alphabetize a list of strings 6 1 2 PROC SCopy purpose to copy one string into another format PROC SCopy lt dest gt lt soorce gt parameters lt dest gt is the identifier of the destination string CHAR ARRAY for the string copy lt soorce gt _ is the string with double quotes or identifier of the CHAR ARRAY used as the source string for the copy description This procedure copies the contents of lt source gt into lt dest gt If lt dest gt is dimensioned to be shorter than the length of lt source gt then only the part of lt source gt
90. different formats 1 Hexadecimal 2 Decimal 3 Character Hexadecimal constants are represented by a dollar sign in front of the number Examples 4A00 0D 300 Decimal constants require no special character to define them as decimal Examples 65500 2 324 46 NOTE Both hexadecimal and decimal numeric constants may have a negative sign in front of them thus 8C 4360 Character constants are represented by a single quote preceding the character Characters are numeric constants because they are internally represented as one byte numbers as per the ATASCII character code set Examples A V String constants consist of a string of zero or more characters enclosed by double quotes When stored in memory they are preceded by their length The double quotes are not considered as part of the string if you want a in your string place two double quotes together see examples Examples This is a string constant a double quote in a string 56395 q a single character string constant Compiler constants are different from the above types of constants in that they are used at compile time to set certain attributes of variables procedures functions and code blocks and are not evaluated at run time The following formats are valid 1 A Numeric Constant 2 A Predefined Identifier 3 A Pointer Reference see section 8 1 2 4 The Sum of Any Two of the Above We have alre
91. drive caeaette etc With these routines you can open a channel an IOCB close a channel and do extensive disk file manipulation 4 1 PROC Open purpose set up an IOCB channel to allow i o using a peripheral device format PROC Open BYTE channel lt filestring gt BYTE mode aux2 parameters channel is a valid channel number 0 7 lt filestring gt is the string constant or array identifier of that string constant used as the device D P S etc being opened on the given channel IOCB number D files also require a filename mode is the number designating the type of I O thus 4 read only 6 read directory 8 write only 9 write append 12 read write update aux2 a device dependent value usually zero description This procedure opens a given channel to the device specified in lt filestring gt The I O mode can be set see table above for the number codes Any device dependent codes are passed through aux2 WARNING do not Open channel 7 because it is used by the ACTION system to do its own screen input You can use channel 7 in your program for getting characters from K but since that assumes that channel 7 is open you need the ACTION cartridge to run the compiled version of the program because ACTION opens channel 7 to K 4 2 PROC Close purpose to close an IOCB channel to a device format PROC Close BYTE channel parameters channel is a valid channel number 0 7 des
92. e lt addr gt lt values gt lt str const gt where lt ident gt is the name of the variable lt size gt is the size of the array and must be a numeric constant lt addr gt is the address of the first element of the array and must be a compiler constant lt values gt sets the initial values of the elements of the array Each value must be a numeric constant lt str const gt sets the initial values of the elements of the array to the string constant with the first element being the length of the string We warned you that it was cluttered But now to organize some of this clutter with some instructive hopefully examples BYTE ARRAY a b declares two arrays with BYTE elements without sizes declared INT ARRAY x 10 deelares x as an INT array and dimensions its size to 10 elements BYTE ARRAY str This is a string constant this declares str as a BYTE sarray and fills it with a string constant CARD ARRAY junk 8000 declares junk as a CARD array which starts at 8000 in memory without any size implied BYTE ARRAY tests 4 7 19 declares tests as a BYTE array and fills in its values PROGRAMMING NOTES You should dimension the size of an array whenever possible but there are some instances where you can t or needn t 1 When you don t know how big it s going to be i e as in a routine parameter when you don t know how big an array Is going to be passed 2 When you are f
93. e etc Part VI The ACTION Library Chapter Introduction Vocabulary 1 1 1 1 2 Library Format Chapter 2 Output Routines 2 1 The Print Procedures 2 1 1 Printing Strings PROC Print PROC PrintE PROC PrintD PROC PrintDE 2 1 2 Printing BYTE Numbers PROC PrintB PROC PrintBE PROC PrintBD PROC PrintBDE 2 1 3 Printing CARD Numbers PROC PrintC PROC PrintCE PROC PrintCD PROC PrintCDE 2 1 4 Printing INT Numbers PROC Printl PROC PrintlE PROC PrintID PROC PrintIDE 2 1 5 PROC PrintF Formatting Output 2 2 The Put Procedures PROC Put PROC PutE PROC PutD PROC PutDE Chapter 3 Input Routines 3 1 Numeric Input BYTE FUNC InputB CARD FUNC InputC INT FimC Inputl BYTE FUNC InputBD CARD FUNC InputCD INT FUNC InputID 3 2 String Input PROC InputS PROC InputSD PROC InputMD 3 3 CHAR FUNC GetD Chapter 4 File Manipulation Routines 4 1 PROC Open 4 2 PROC Close 4 3 PROC XIO 4 4 PROC Note 4 5 PROC Point Chapter 5 Graphics and Game Controllers 5 1 PROC Graphics 5 2 PROC SetColor 5 3 BYTE color 5 4 PROC Plot 5 5 PROC DrawTo 5 6 PROC Fill 5 7 PROC Position 5 8 BYTE FUNC Locate 5 9 PROC Sound 5 10 PROC SndRst 5 11 BYTE FUNC Paddle 5 12 BYTE FUNC PTrig 5 13 BYTE FUNC Stick 5 14 BYTE FUNC Strig Chapter 6 String Handling Conversion 6 1 String Handling Routines 6 1 1 INT FUNC SCompare 6 1 2 PROC SCopy 6 1 3 PROC SCopyS 6 1 4 PROC SAssign 6 2 Number to String Conversions PROC StrB PROC StrC PROC Strl 6 3 Str
94. e you will usually get the compiler error Bad Expression The truth table below shows what each of these operators will do in a given situation exp 1 and exp 2 are the simple relational expressions on either side of the special operator true and false are the possible results of a relational test RELATIONALS RESULTS Exp1 Exp2 AND OR False False False False False True False True True False False True True True True True NOTE you may use parentheses around one segment of a complex relational expression to insure the order of evaluation If you don t do this the expressions are evaluated in left to right order see Examples WARNING at the writing of this manual the ACTION compiler sees the pairs AND amp and OR as synonyms and they are evaluated in the same way bit wise If you follow the rules outlined above when using them you should have no problems Also if you stick to using AND and OR only in the relational sense and amp and only in the bit wise sense your programs will be compatible with possible upgrades of ACTIONI Here are some samples of valid complex relational expressions cat lt 5 AND dog lt gt 13 ptr 7 3 60FF AND ptr lt 1FFF X F000 OR dog gt 100 8 amp cat lt 10 OR ptr lt gt 0D cat lt gt 0 AND tdog gt 400 OR dog lt 400 ptr D456 OR ptr E000 OR pir 600 Here s a confusing situation FO AND 0F
95. e Screen lt CTRL gt lt SHTFT gt lt down arrow gt Left 1 Char lt CTRL gt lt SHIFT gt Right 1 Char lt CTRL gt lt SHIFT gt E 5 Text Entry Enter Program enter text Next Line lt RETURN gt Control Chars precede each character with lt ESC gt E 6 Delete Text Back 1 Char lt BACK S gt Cursor lt CTRL gt lt DELETE gt Delete Line position cursor on line lt SHIFT gt lt DELETE gt E 7 Insert Replace Text Toggle Modes lt CTRL gt lt SHIFT gt Insert Line lt SHIFT gt lt INSERT gt E 8 Restore Altered Line Restore Line don t move cursor lt CTRL gt lt SHIFT gt U Recall Line don t move cursor lt CTRL gt lt SHTPT gt P E 9 Text Blocks Load Block position cursor lt SHIFT gt lt DELETE gt until done Paste Block position cursor lt CTRL gt lt SHIFT gt P E 10 Searches Substitutions Find String lt CTRL gt lt SHIFT gt F enter string Substitute lt CTRL gt lt SHIFT gt S enter new string lt RETIIRN gt enter old string E 11 Breaking amp Combining Lines Break Line position cursor lt CTftL gt lt SHIFT gt lt RETURN gt Combine put cursor at front of second line Line lt CTRL gt lt SHIFT gt lt BACK S gt E 12 Leaving the Editor Leave Editor lt CTRL gt lt SHIPT gt M Appendix F Summar
96. e made changes to the file viewed through that window and have not saved the changed version the message area will prompt you with Not saved Delete to make sure that you know that you have not saved the new version When you delete a window the screen space it occupied is given bach to the other window If you delete window 1 then window 2 becomes window 1 since there is only one window it must be window 1 2 7 Moving Copying Blocks of Text The ACTION Editor allows you to move or copy text blocks through the use of a copy buffer Whenever you use the command lt SHIFT gt lt DELETE gt to delete a text line that line is temporarily stored in a region called the copy buffer You may then paste that deleted line using lt CTRL gt lt SHIFT gt P The copy buffer is cleared every time you use the lt SHIFT gt lt DELETEs with one exception If you use the lt SHIFT gt lt DELETE gt consecutively i e without doing any other commands or text entry between the deletes the copy buffer is not cleared Instead the second and following deleted lines are also stored in the copy buffer thus loading it with a text block Now when you use the lt CTRL gt lt SHIFT gt P command the entire text block in the copy buffer is pasted back into the text Enough of the overview on to the method itself To move a block of text position the cursor on the first line of the block and press lt SHIFT gt lt DELETE gt until you have de
97. e of barray to point to the starting address of the new string The old string is still in memory but nothing is pointing to it any more so it is inaccessible Notice that PrintE barray is valid because barray points to a valid string constant which is the type of parameter the PrintE library procedure requires Pretty sneaky Example 3 PROC equatearrays BYTE ARRAY a This is a string constant barray barray a PrintE a PrintE barray RETURN Output 3 This is a string constant This is a string constant EXAMPLE 3 NOTES All this program does is show you that you can equate two arrays simply by making them point to the same memory location in this case it s a string constant they re both pointing to You might have noticed that we have not done anything like BYTE ARRAY a A s t r i n g PrintE a That s because the above won t work Remember that string constants are different from simple strings because their first byte contains their length so procedures that expect a string constant will balk when you attempt to send them anything else And now for a program that uses all the applications of arrays which we have discussed Example 4 SCENARIO You have a program that only gives error numbers when the user makes an error and you want it to print out error messages as well You could do this using arrays as in the following program We will discuss how the program works after the progr
98. e random number description This function will return a random number between 0 and range If range is 0 then a random number between 0 and 255 is returned 7 2 PROC Break purpose to stop program execution format PROC Break parameters none description This procedure allows you to stop your program s execution to examine variables and do other debugging You can continue program execution starting with the statement following the Break routine call by using the PROCEED monitor command 7 3 PROC Error This is the procedure the ACTION system itself calls when it or CIO encounters an error If you want to trap your own errors you could write a routine to do this and then make ACTION use your error routine instead of its own simply by having the following statements in your program PROC MyError BYTE errcode this is your error routine and the error code number is passed to it by the ACTION system your error handling routines go here RETURN end of PROC MyError PKOC main your main procedure CARD temperr holds the address of the system s error routine PROC Error temper Error save the address of the system error routine Error MyError make the address of the system error routine point to the start of your error routine sthe body of your program goes here Error temperr reset the address of the system error sroutine back to the real system error rroutine not yours RE
99. e you to a complete software development system one in which you can perform all of your programming tasks If you have programmed your Atari using Atari BASIC you will discover that ACTION runs a lot faster has a better editor and is just as easy to learn If you have ever done assembly language programming you will find that ACTION is almost as fast as assembly language as far as program execution is concerned You will also find that programming ACTION is much quicker and easier due to the nature of the language its editor and its library of routines For those of you with very little or no previous programming experience we suggest that you read this manual very carefully and be sure you understand one concept before moving on to the next We say this because this is not a tutorial to teach you the ACTION system but rather a reference manual of all the capabilities of the system That is not to say that you won t understand what you re reading quite the contrary it simply means that we don t discuss every possible programming use of the concepts involved We respect your ingenuity and curiosity and believe that you yourself will find some uses we haven t even dreamt of 1 Notes On This Manual The manual itself is separated into six parts and a group of appendices Each of the parts exclusively discusses one facet of the ACTION system thus enabling you to learn about the different components of ACTION without hav
100. eed 3 PrintC spaces ELSEIF c1 c2 lt 100 THEN double digits Print need 2 spaces ELSE triple digits need 1 Print space only FI end of digit spacing PrintB c1 c2 print the result OD end inner loop PutE put out a carriage return OD end of outer loop RETURN end of PROC timestables Output 2 3 4 5 6 7 8 9 10 4 6 8 10 1214 16 18 20 6 9 12 15 18 2124 27 30 8 12 16 20 24 2832 36 40 10 15 20 25 30 3540 45 50 12 18 24 30 36 4248 54 60 14 21 28 35 42 4956 63 70 16 24 32 40 48 5664 72 80 18 27 36 45 54 6372 81 90 020 30 40 50 60 7080 90100 OONDOORWND As you can see from the above examples nesting can be used to accomplish quite a bit if you know what you re doing Fortunately knowing what you re doing doesn t take too much time because the concept of nesting is universal to all structured statements Once you understand it as applied to one statement you can apply it to all of them Chapter 6 Procedures and Functions Procedures and functions are used to make your ACTION program more readable and usable Almost everything we do is a procedure or function in some way or other For example look at this table Procedures Functions Washing the car Balancing your checkbook Doing dishes Looking up a phone number Driving to work Going to school What makes these procedures and functions Well for each there s 1 a group of related actions done to
101. element of nums to the screen Print put a space between characters OD PutE RETURN Output 1 ABCDEFGHIJ There are two array references in the above program nums x in the assignment statement and nums x as a parameter to the Put library procedure They and all other array references have the form lt identifier gt lt subscript gt where lt identifier gt is the name of the array you want to reference lt subscript gt is the number of the element in that array and is an arithmetic expression As mentioned In the comment explaining the FOR loop array subscripts do not start at 1 as you might expect The first element in array cat is cat 0 not cat 1 This might seem strange but you get used to it very quickly Example 2 PROC changearray BYTE ARRAY barray barray This is string 1 PrintC barray sprints the CARD barray contains Print PrintE barray sprints the string barray points to with an EOL barray This is string 2 PrintC barray Print PrintE barray RETURN Output 2 10352 This Is string 1 10414 This is atring 2 EXAMPLE 2 COMMENTS Notice from the output that the address to which barray is pointing changes Reassigning the whole array When doing it using string constants does not put the new string into the memory space occupied by the old one but rather allocates new space for the new string and then changes the valu
102. enclosed in single quotes USAGE OF lt AND gt When talking about a key on the Atari keyboard we will enclose it with the characters lt and gt thus lt BACK SP gt the backspace key Some of the keys have more than one label written on them In these cases the label best describing the Editor command will be used There is one exception to the above the character A Z and digit 0 9 keys are not enclosed by the angle brackets MULTI KEYSTROKE COMMANDS Some of the Editor commands require that you press more than one key at a time For these commands the keys required are given back to back in the order in which you should press them For example lt SHIFT gt lt DELETE gt means that you should hold the key marked SHIFT down and then press the key marked DELETE THE MESSAGE AREA Throughout this part of the manual the term message area will be used This area is simply the inverse video line you will notice at the bottom of your screen when you enter the Editor This line normally has ACTION c 1983 ACS written on it but is used by some of the editor commands to ask you questions give you information or report an error When you are using two windows see section 3 4 the message area line separates the two windows DEFAULT USER RESPONSE Some of the commands which use the message area to exchange information with you remember the information you gave the last ti
103. ere passed back into number the output would be 713 1 713 713 2 356 356 3 118 118 4 29 29 5 5 5 6 0 0 7 0 0 8 0 0 9 0 0 10 0 The flow of information through parameters is one way Information can be sent to a routine through parameters but information generally may not be sent out using parameters If you want to send a single value back from a routine make that routine a function and then you can send it back in the function RETURN statement If you want to send out more things you can uee global variables or you can pass pointers as parameters see 9 5 A Note On Parameter Pairing When you call a routine that has parameters the first parameter you give in the call will go into the first variable in the list of parameters in the routine declaration the second will go into the second and so on You can pass fewer parameters than the routine requires but no more For example if there are 5 parameters in the declaration you could pass the routine 0 to 5 parameters This allows you to write routines that require a variable number of parameters depending on the job it must do HINT if you do this the first parameter should probably be the number of parameters being passed A Note On Type Compatibility If the value you pass as a parameter and the value expected by the routine are of different data types you won t get a compiler error because the ACTION compiler insures parameter type compatibi
104. es each element of the array an implicit pointer to a string All we have to do is assign the value of the proper array element i e the one pointing to the needed error message to the BYTE array errmsg thus making errmsg point to the proper message Then we just print out the message We understand that the above program is very confusing until you completely understand the concept of arrays and their internal representation but it is here so that you can see some of the advanced capabilities of arrays 8 3 Records Records are constructions which allow you to group together some pieces of information which although related in some way are not of the same type Your driver s license is an example of a record It has your name photo address and license number all together These pieces of information belong together in that they all describe you to some degree but they are of different types Your name is a character string your photo is a picture and your address is made up of both numbers and characters as is your license number Of course the ACTION language doesn t support all these types Instead it groups together only the types of information the compiler understands the fundamental data types 8 3 1 Declaring Records ACTION records manipulate the fundamental data types by creating a new data type composed of one or more of the fundamental types Then you declare variables of that type just as you declare variabl
105. es of type BYTE INT or CARD This allows you to declare as many variables of one record type as you want without having to redeclare the format of the record type every time The next section 8 3 1 1 shows bow to create a record data type and section 8 3 1 2 demonstrates how to declare variables of a predefined record type 8 3 1 1 The TYPE Declaration Without further ado we ll present the form used to declare a record data type TYPE lt ident gt lt var decls gt where TYPE is the keyword denoting the definition of a record type lt ldent gt is the name of that record type lt var decls gt are valid variable declarations as in section 3 4 1 except that the lt Init info gt option shown there is forbidden At this point an example would probably help TYPE rec BYTE b1 b2 stwo BYTE fields first INT i1 then one INT field CARD c1 c2 c3 toen three CARD fields BYTE b3 sending with a BYTE This needs some explanation so we ll go through it piece by piece TYPE rec We are defining a new data type called rec BYTE b1 b2 The first two fields of this type are of BYTE type and are called bl and b2 INT i1 The third field is of type INT and its name is i1 CARD C1 C2 C3 The fourth through sixth fields are CARD type and are named c1 c2 and c3 respectively BYTE b3 The seventh and final field of the record type rec is of BYTE type and is called b3 Notice that there are
106. ess Guess InputB get the user s guess Nujnguesses 1 add 1 to number of guesses IF guess lt num THEN guess too low PriritE Too low try again ELSEIF guess gt num THEN _ guess too high PrintE Too high try again ELSE guess just right PrintE Congratulations Print You got it in PrintCE numguesses IF numguesses lt goal THEN beatgoal 1 Fl Fl end of guess testing UNTIL guess num loop control OD end of UNTIL loop RETURN end of PROC playgame BYTE FUNC stop This function finds out if the player wants to play another game BYTE again PrintE Do you want to play Print another game Y or N again GetD 1 get player s response from K to avoid getting a RETURN as the first guess of the next game PutE IF again N OR again n THEN doesn t RETURN 1 want to play Fl RETURN 0 end of FUNC stop PROC main Close 1 just for safety s sake Open 1 K 4 0 open K to read only Intro sprint out the introduction DO Numgames 1 increment total number of qames playgame splay the game once tally show tally of games thus far UNTIL stop doesn t want to play anymore OD PutE PrintE Come play again soon Close 1 close K RETURN end of PROC main The following table shows how this program uses variables It gives the variable name it s scope it s availability and use in each routine KEY A variable Available for use in routine
107. essions Since a conditional expression is involved in a test there are only two values it may have true or false This does not mean a conditional expression is a new type of expression however In fact a conditional expression is simply either a relational or arithmetic expression Only the interpretation is different The following table shows what the conditional interpretation is depending on which type of expression it is Expression Type Normal Result Conditional Result arithmetic zero 0 false non zero true relational false false true true 5 2 1 2 IF Statement The IF statement in ACTION 1 is much li ke the if conditional statement in English For example If have 9 or more I ll buy the steak In ACTION the same statement might be BYTE money steak 9 fish 8 chicken 6 hotdog 2 IF money gt 9 THEN Buy steak money Fl NOTE buy Steak money is a procedure call and will be dealt with in section 6 1 3 From the above example you can see that the basic form of the IF statement is IF lt cond exp gt THEN lt statements gt FI FI is not part of fe fi fo fom but IF spelled backwards and a keyword to the compiler showing the end of an IF statement Since IF can work on a list of statements we need Fl to terminate that list Without this keyword the compiler would not know how many of the statements following the THEN went with the IF statemen
108. ey are used to change the page formatting not the data element formatting A maximum of five controls are allowed and each data element requires its own control Characters in the control string which are not themselves controls are output directly that is exactly as they are in the string 2 2 The Put Procedures The Put group of library routines are used to output single characters i e output BYTE type data as an ATASCII character These routines use options very similar to those in Print and so the options need not be re introduced here purpose to output a single ATASCIl character using specified format options formats PROC Put CHAR character PROC PutE PROC PutD BYTE channel CHAR character PROC PutDEBYTE channel CHAR character parameters character is an arithmetic expression remember that arithmetic expressions can simply be a constant or variable name channel is a valid channel number 0 7 description These procedures output characters as follows Put outputs the character to the default channel without a lt RETURN gt at the end PutE outputs an EOL lt RETURN gt character to the default channel PutD outputs the character to a specified channel without a lt RETURN gt at the end PutDE outputs the EOL lt RETURN gt character to a specified channel Chapter 3 Input Routines In this chapter we discuss the routines which complement the Print and Put routines that is th
109. ey input data from somewhere Similar to the Output routines the type of data that is input and where it comes from is defined through the use of options Input and Get are the input routines and each has its own set of options very similar to those available in the output routines The Input routines are grouped into two categories those which input numeric data and those which input string data Each will be dealt with separately There is only one Get routine GetD and it will be discussed in the last section of this chapter 3 1 Numeric Input The following six functions allow you to input any type of numeric data from any channel We have grouped them all together because they are very easy to understand and so do not require separate sections as did the routines used to output numbers did purpose to input numeric data formats BYTE FUNC InputB BYTE FUNC InputBD BYTE channel CARD FUNC inputC CARD FUNC InputCD BYTE channel INT FUNC Inputl INT FUNC InputID BYTE channel parameters channel is a valid channel number 0 7 description The functions input data as follows InputB InputBD InputC InputCD Inputl InputID 3 2 String Input inputs a BYTE number from the default channel inputs a BYTE number from a specified channel inputs a CARD number from the default channel inputs a CARD number from a specified channel inputs an INT number from the default channel inputs an INT number from a spec
110. form ba c b ba POKE C B Poke c b or in better ACTION form ba c ba b GRAPHICS 8 Graphics 8 COLOR 3 color 3 Note color is a system library variable and is predefined by ACTION DRAWTO C D DrawTo c d LOCATE C D B b Locate c d PLOT C D Plot c d POSITION C D Position c d SETCOLOR_ 0 1 C SetColor 0 1 c GRAPHICS 24 COLOR C PLOT 200 150 DRAWTO 120 20 Graphlcs 24 color c Plot 200 150 DrawTo 120 20 POSITION 40 150 Fill 40 150 POKE 765 C XIO 18 6 0 0 S SOUND 0 121 10 6 Sound 0 121 10 6 C PADDLE B c Paddle b C PTRIG B c Ptrig b C STICK B c Stick b C STRIG B c Strig ti B S SCopy ba s B S 3 5 SCopyS ba s 3 5 B 3 5 S SAssign ba s 3 5 B INT 6 RND 0 1 b Rand 6 1 FOR C 4000 TO 5000 POKE C 0 NEXT C Zero 4000 1001 STOP Break B STR 1 Strl i ba VAL S i Vall s ACTION The Best Complete Software Development System The Fastest High Level Language Available for the Atari A versatile structured language that runs at al most assembly language speeds 100 times faster than BASIC Best Structured Language Incorporates features found in PASCAL C ALGOL and ADA yet has many of the same commands familiar to Atari BASIC programmers Has Everything You Need THE E
111. function tests x for overflow and sreturns its square if valid IF invalid the function prints an error message and returns 0 IF x gt 255 THEN number would cause overflow PrintE Number too big RETURN 0 return a zero FI RETURN x x return x squared See how easy it is The use of multiple RETURNS can come in very handy when you are testing a lot of different conditions each requiring that a different value be returned NOTE As mentioned in section 6 1 2 the compiler can t tell if you leave out a RETURN so you must make sure you have one 6 2 3 Calling Functions You have already seen two examples of function calls They can be found in section 5 2 4 2 WHILE example 2 and section 5 2 4 3 UNTIL example 1 If you look at those programs you ll see the lines num Rand 101 guess InputB The first is an example of calling a function that requires parameters and the second an example of calling one without parameters Both Rand and InputB are library functions Rand returns a random number between 0 and the number you give it in the above case 101 minus one InputB reads a byte value from the default device the screen Notice that both of them returns a value Because this value must go somewhere or be used somehow function calls must be used in arithmetic expressions In the above two cases the arithmetic expressions consist of the function call only and are used in assignment
112. he amount by which the computer increments the counter after every iteration lt DO OD loop gt is a DO OD infinite loop NOTE the STEP lt inc gt is optional Instead of trying to explain this to you using metaphors we ll throw a few examples at you because they more or less speak for themselves Following each is its output Example lr PROC hithere BYTE ctr counter used in FOR loop FOR ctr 1 TO 5 this FOR loop has no STEP so DO an increment of 1 is assumed PrintE Hi there OD RETURN Output 1 Hi there Hi there Hi there Hi there Hi there Example f2 PROC evens BYTE ctr counter used in FOR loop FOR ctr 0 TO 16 STEP 2 this FOR loop has a STEP DO PrintB ctr Print RETURN Output 2 0246810121416 Look back at the format of the FOR statement Notice that we said nothing about using numeric variables as lt initial value gt lt final value gt or lt inc gt Doing this is legal and allows you to make FOR loops execute a variable number of times If you change the value of the variables used as lt initial value gt lt final value gt or lt inc gt in the loop itself you won t change the number of times the loop is executed This is true because lt initial value gt lt final value gt and lt inc gt are set with a constant value when you enter the loop If you do use variables the value used when setting these is the value the variable had when the loop was first e
113. he same data type BYTE b1 b2 b3 b4 INT it CARD c1 b3 D puts the ATASCII code number for D into the byte reserved for b3 b4 44 puts the hex number 44 into the byte reserved for the BYTE variable b4 44 is D in ATASCII and so p3 and b4 now contain the same thing b1 b4 16 adds 16 to the numerical value of b4 and puts the result into the byte reserved for b1 C1 23439 07D8 puts the value 21431 S53B7 in the two bytes reserved for c1 it ct 1 puts the value 21431 SAC49 in the two bytes reserved for i1 b2 i1 puts the value 49 73 into the byte reserved for b2 Notice that the computer takes the LSB of il to put into b2 the MSB of il is AC the LSB is 49 b2 b2 1 adds 1 to the current value of b2 and stores the sum back into b2 b2 now contains 4A 74 Notice that the last example s form is lt var gt lt var gt lt operator gt lt operand gt Since programmers often use the above format ACTION allows the following shorthand form to do the same thing lt var gt lt operator gt lt operand gt The operator must be either arithmetic or bit wise The operand must be an arithmetic expression form The following are some examples of this shorthand b2 1 is the same as b2 b2 1 b2 b1 is the same as b2 b2 b1 b2 amp 0F is the same as b2 b2 amp Of
114. his will get you out of any command safely NOTE appendix E provides a summary of the Editor commands listed by the command itself instead of what it does 2 1 Getting to the Editor When you first enter the ACTION system you will automatically be put into the Editor so there is nothing involved in getting to it You re already there If you leave the ACTION system and go to DOS OS A DOS XL or Atari DOS you will be in the Monitor when you re enter ACTION there is one exception to this see NOTE below To get to the Editor from the Monitor you need only type E lt RETURN gt This will put you directly into the editor NOTE if you are using OS A or DOS XL and you execute a DOS extrinsic command before returning to the ACTION system you will not be put into Monitor as stated above but straight into the Editor This is not the case with Atari DOS since it has no extrinsic commands 2 2 Leaving the Editor There is only one way to leave the Editor aside from turning off the computer lt CTRL gt lt SHIFT gt M This command will cause you to go from the Editor to the Monitor where you may call the other components of the ACTION system or leave the system altogether and go to DOS 2 3 Text Entry There is no special Editor command to allow you to enter text You simply type it in as on a typewriter When you have reached the maximum line length the Editor will buzz every time you put in another character
115. iables by making each variable in the list accessible using only the array name and a subscript The variables in the list must be of the same data type and only the fundamental data types are allowed The array name tells which array you want and the subscript tells which element of that array you want The subscript is just a number so what you re really saying when you reference an array element is want the n th element of array x where n is the subscript and x is the array name In the following section we will discuss the internal representation of an array After that we ll show you how to declare arrays and manipulate them and then we ll talk about the limitations of arrays in ACTION 8 2 1 Array Declaration Declaring arrays is easy in ACTION but that doesn t mean that you don t have much control over what s going on There are many options you can use to define different characteristics of the array including its address its size and even its initial contents Because of all these options the format looks somewhat cluttered but the examples should clear up any confusion lt type gt ARRAY lt var init gt lt var init gt where lt type gt is the fundamental type of the elements of the array ARRAY is the keyword denoting an array lt var init gt is the information required to declare one variable as an array of lt type gt data type elements lt var init gt has the form lt ident gt siz
116. ified channel String inputting is accomplished by suffixing the Input base with the character S There are three such procedures in the ACTION Library and they allow you to input a string from any channel and or define the maximum length of the input string purposes formats parameters description to input string data PROC Inputs lt string gt PROC InputSD BYTE channel lt string gt PROC InputMD BYTE channel lt string gt BYTF max lt stririg gt is the identifier of a BYTE ARRAY channel is a valid channel number 0 7 max is the maximum length allowable for the input string The string is truncated to max length if it is too long Here is an outline of what each procedure does InputS InpatSD InputMD inputs a string of up to 255 characters from the default channel inputs a string of up to 255 characters from a specified channel inputs a string of up to max characters from a specified channe 3 3 CHAR FUNC GetD purpose to input a single character from a given channel format CHAR FUNC GetD BYTE channel parameters channel is a valid channel number 0 7 description This function is used to get one character from the device specified by channel The character is returned through the function as its ATASCII character set number Chapter 4 File Manipulation Routines This chapter is devoted to those routines which deal with external devices printer disk
117. igher the pitch distortion is a measure of the sound s fuzziness 0 14 even values volume is the volume of the sound 0 16 This procedure allows you to control the sound generating apparatus on the ATARI much like the BASIC command of the same name Distortion values 10 is the only one useful for making music The others are useful for airplane racecar etc sound effects Here is a table for various musical notes using distortion 10 pitch Note Comment 29 C High Notes 31 B 33 A Bb 35 A 37 G Ab 40 G 42 F Gb 45 F 47 E 50 D Eb 53 D 57 C Db 60 C 64 B 68 A Bb 72 A 76 G Ab 81 G 85 F Gb 91 F 96 E 102 D Eb 108 D 114 C Db 121 C Middle C 128 B 136 A Bb 144 A 153 G Ab 162 G 173 F Gb 182 F 193 E Lower Notes 204 D Eb 217 D 230 C Db 243 C 5 10 SndRst purpose to reset all the sound voices format PROC SndRat parameters none description This procedure resets all the sound voices to produce no sound 5 11 BYTE FUNC Paddle purpose to return the current numeric value position of one of the paddles format BYTE FUNC Paddle BYTE port parameters port is the port number 0 7 of the desired paddle description This function returns the current value of the specified paddle port 5 12 BYTE FUNC PT
118. illing the array in the declaration using either the lt values gt or lt str conat gt construction and you aren t planning to add to the array Also remember that the first byte of a string constant contains the length of that string So to make a string longer first you must change the length byte which is element 0 of the array that contains the string 8 2 2 Internal Representation The internal representation of an array is very much like that oOf a pointer This is because the array name is actually a pointer to the first element of the array The array itself is simply a contiguous group of cells each containing an array element The size of a cell is determined by the data type of the elements one byte cells for BYTE type two byte cells for both INT and CARD types However having the array name be a pointer leads to some very interesting ramifications as shown in examples 2 through 4 of the following section 8 2 3 Array Manipulation Using and manipulation arrays is not very difficult once you know how to declare the array and reference its elements You already know how to declare arrays so now we ll show you how to reference elements Example 1 PROC reftest BYTE x BYTE ARRAY nums 10 FOR x 0 TO 9 _ although nums is ten elements slong the subscripts run from 0 to 9 not 1 to 10 DO nums x x A creates the alphabet the xth element of nums is assigned x A Put nums x output the xth
119. ince Atari DOS and some of Its utilities use the same memory that ACTION uses you should always take the precaution to save all files before going to Atari DOS 2 4 EDIT Transfer to the ACTION Editor You can transfer to the ACTION editor by entering EDITOR then pressing lt RETURN gt Examples EDITOR lt RETURN gt E lt RETURN gt NOTE if you were just compiling a program from the editor and the compile failed due to a syntax error you will find that the ACTION editor cursor is on the line following the error 2 5 OPTIONS The Options Menu The options menu allows you to alter certain operational parameters of the ACTION Monitor Compiler and Editor Enter the options menu by entering OPTIONS then pressing lt RETURN gt Examples OPTIONS lt RETURN gt O lt RETURN gt Each option is displayed in the command line If you want to change that option type in the value you want and press lt RETURNS gt If you don t want to change that option simply press lt RETURN gt If you want to exit the options menu all together press lt ESC gt NOTE a summary of the options available may be found in appendix G Following is a description of each of the options Available Each description contains the command line prompt for that option the initial state of that option and the components of the ACTION system that option affects M Monitor C Compiler E Editor Display Y M C E The screen displa
120. ine length 240 Left margin 2 Oto Controls left margin in window set as 39 low as you find comfortable EOL character 9B any ATASCII character Change the End Of Line character to aid visualization of program Appendix H PRIMES Benchmark This is the benchwark that from September 1981 BYTE Magazine pp 160 198 as implemented in ACTION Here is a table of our times to compare with those in the magazine Mode Time Compilation 0 25sec Display OFF 12 2sec Display ON 17 9sec DEFINE size 8190 ON ga Hi OFF o BYTE ARRAY flags size 1 CARD count I k prime BYTE DISPLAY 22F iter tick 20 tock 19 PROC Primes DISPLAY 0 comment this line to leave display On tick 0 tock 0 FOR iter 1 TO 10 DO count 0 turn flags on non zero SetBlock flags size ON FOR i 0 TO size DO IF flags i THEN prime i i 3 PrintCE prime Uncomment to print primes k prime i WHILE k lt size DO flags k OFF k prime OD count 1 FI OD OD i tick 256 tock DISPLAY 22 turn display back on PrintF U Primes done in U ticks E count i RETURN Appendix l Converting BASIC Concepts to ACTION Programs This appendix presents several BASIC functions routines statements etc For each BASIC example given a corresponding ACTION example is also given In the BASIC examples given no line numbers are shown unless necessary for illustration purposes
121. ines and its symbol tables When called the first thing the ACTION Compiler does is to decide where to put the code it will generate as it compiles your ACTION source program It does this by looking at memory location 14 The CARD value this and the following location contain gives the address of the start of free memory This address will vary depending on the size of the Editor buffer see appendix B Unless you specify otherwise the compiler will put your compiled code in memory starting with this address To tell the compiler where you want your program compiled give the following two commands to the Monitor right before you compile SET 14 lt address gt SET 491 lt address gt Where lt address gt is the starting address for the compiled code 2 1 Comments SET DEFINE Neither comments the SET directive nor the DEFINE directive generate any machine code This is because they do not do anything at run time and so are not required 2 2 Variable Allocation Information on variables is stored in two different locations by the ACTION Compiler in the code itself and in the symbol table The symbol table is discussed later Variables are stored in front of the machine code where they are used Some variables are declared before the first routine is entered These variables called global variables can be used by any succeeding routine They need no additional declaration within the routine The allocated variab
122. ing to Number Conversions BYTE FUNC VaIB CARD FUNC ValC INT FUNC Vall Chapter 7 Miscellaneous Routines 7 1 BYTE FUNC Rand 7 2 PROC Break 7 3 PROC Error 7 4 BYTE FUNC Peek CARD FUNC PeekC 7 5 BYTE FUNC Poke CARD FUNC PokeC 7 6 PROC Zero 7 7 PROC SetBlock 7 8 PROC MoveBlock 7 9 BYTE device 7 10 BYTE TRACE 7 11 BYTE LIST 7 12 BYTE ARRAY EOF 8 Part VI THE ACTION Library Chapter 1 Introduction The ACTION library makes it possible for you to do a lot of common I O and graphics routines without having to write them first The ACTION cartridge contains almost 70 prewritten routines which you can call as though they were routines written by you This convenience can save you quite a bit of time and effort whether you are a beginning or advanced programmer 1 1 Vocabulary Most of the vocabulary used in this part has been defined previously but there are two terms we ll use often which require some discussion IOCB and channel IOCB stands for Input Output Control BlocK The ClO Central I O uses ICOBs to perform I O functions The ACTION library I O routines set up an IOCB to tell the ClO what it the routine wants done and then makes a direct call to CIO The IOCBs are numbered 0 7 When you use routines which require channel numbers the number is actually the number of the IOCB which contains the information about a given peripheral device That does not mean that certain IOCBs handle certain peri
123. ing to keep flipping pages Each part is prefaced by a table of contents an introduction and a vocabulary The one drawback to separating the ACTION system into its component parts is that you will learn everything about one part before starting the next part To help alleviate this problem we suggest that you read the introduction section of each of the parts before reading one part in depth Also the last chapter of this introduction shows you how the ACTION components work together to allow you to run programs Chapter 1 The ACTION System The ACTION system is made up of five different parts The ACTION Monitor The ACTION Editor The ACTION Language The ACTION Compiler The ACTION Library The Monitor is the boss of the ACTION system Through it you can call the Editor the Compiler or get access to some system options This is the monitor s only job but it is a important one allowing you to decide which part of the ACTION system you want to use at any given time The Editor is where you create new programs and modify old ones It doesn t know anything about the ACTION language or compiler that is it s simply a text editor and doesn t check language syntax so you can use it for other word processing or program entry applications The Editor also allows you to save the text in the editor buffer or read text from a peripheral device disk drive cassette et into the editor buffer The ACTION Language is what you use
124. inter to the start of the destination memory block source is a pointer to the start of the source memory block size is the size of the block you want to move description This procedure moves the values in a block starting at address source and ending at address source size 1 to a block starting at address dest and ending at address dest size 1 If dest is greater than source and there is not size space between them then the move will not work properly because part of the source you are trying to move is in the dest space 7 9 BYTE device device is a variable defined in the ACTION Library and allows you to control the default channel device for i o The number contained by device is the channel number of the default device so for example you send default output to the printer using the following statements Close 5 avoid a File already Opened error Open 5 P 8 device 5 and then reset it to the screen when you want to using the following statements Close 5 close P device 0 7 10 BYTE TRACE This library variable allows you to control the TRACE compiler option from within your program You must use it with the SET compiler directive and it must come at the beginning of your program Setting TRACE to 0 turns off the option and setting it to 1 turns it on Example SET TRACE 0 7 11 BYTE LIST This library variable controls the LI
125. ional global variables MODULE Additional global variables arrays and records can be added as needed through the use of the MODULE keyword The variables are assigned space following the last previous routine The identifiers are also included in the compiler s global symbol table 2 6 Symbol Tables The ACTION Compiler maintains two symbol tables one for the global variables and one for the local variables from the last compiled routine The symbol tables are accessible from the ACTION Monitor through the and SET commands see Part Ill They are also used by the ACTION compiler whenever a variable s address is required The Compiler allocates 8 memory pages 2k for these tables located right at the top of available memory Because they are placed there you can wipe them out if you run a program which changes into a graphics mode which requires more memory than graphics 0 This means that you won t be able to go back to the Monitor during program execution and look at the values in your variables The Compiler will have no record of their existence since you just overwrote them Chapter 3 Using The Options Menu The options menu offers you several ways to enhance or alter the performance of the ACTION compiler The various options are discussed here and in part Ill The options are also summarized in Appendix G Increasing compiler speed You can gain at least a 30 improvement in compilation speed by u
126. ions in ACTION ACTION DOS compiled Monitor program Part III ACTION ACTION Editor Compiler Part Il Part V Appendix D ACTION Options Menu Part Ill The monitor is characterized by an inversee video line across the top of the screen containing the prompt gt and the cursor at the left margin 1 1 Vocabulary Term Where Defined lt address gt Part IV lt compiler constants gt Part IV lt filespec gt Below lt ldentifier gt Part IV lt statement gt Part IV lt value gt Part IV When the term lt filespec gt is used in this part it refers to a standard Atari file specifier consisting of a device P C case of disk drives D1 D2 etc and a file name in the 1 2 ACTION Monitor Concepts and Features The ACTION monitor contains two chief features the command line and the message area Both are described below These areas are unique to the ACTION monitor However the ACTION compiler uses a similar screen format see part IV on the ACTION compiler You communicate with the ACTION monitor through the command line The command line is the inverted video line at the top of the screen It contains both the prompt and the cursor at the beginning of the line Commands are recognized by the first character entered after the prompt gt Thus E Edit and Ejunk all tell the ACTION monitor to call the ACTION Editor The various ACTION
127. ip with window 1 the two windows have a combined size of 23 lines When there are two windows each can contain no less than 5 lines and no more than 18 lines Enter the number of lines for window 1 then press lt RETURN gt An entry greater than 18 is converted to 18 and an entry less than 5 is converted to 5 Line size 120 E The line length is the number of characters in the line counting from the left margin see next option The line length is used to help you control the size of lines listed to the printer The bell sounds whenever the actual number of characters in the line exceeds the entered line length You enter the number of characters of the line length WARNING you can set the line length to a value which is out of the correct range The options menu does not check for this error Lines longer than 240 characters are arbitrarily shortened by the ACTION Editor Left margin 2 M E The left margin is the starting point for the line count mentioned earlier This option is offered so that you can get the full use of a screen which displays the leftmost 2 characters not all TV screens can do this It is suggested that you keep the left margin as close to the left edge of the screen as you feel comfortable with Normally setat 2 you can set the left margin as low as 0 and as high as 39 Enter the appropriate left margin location and then press lt RETURN gt WARNING Do not enter a number greater than 39 when using an
128. iven number 6 3 String to Number Conversions purpose to convert a string composed of digits into a number format BYTE FUNC ValIB lt string gt CARD FUNC ValC lt string gt INT FUNC Vall lt string gt parameters lt source gt is a string with double quotes or identifier of a CHAR ARRAY composed of digits 0 Q only description These functions will return the numeric value BYTE CARD or INT depending on the function used of the given string Chapter 7 Miscellaneous Routines This chapter contains those routines which don t really fit into any category but are useful nonetheless The routines themselves are Rand a random number generator Break a routine useful when debugging Error a system routine you can replace Peek view a byte of memory PeekC view two bytes of memory as a CARD Poke put a BYTE value into memory PokeC put a CARD value into memory Zero zero out a section of memory SetBlock fill a block of memory with a value MoveBlock move a block of memory Device the default device variable Trace controls the TRACE compile option List controls the LIST compile option EOF contains EOF status for all channels As you can see the tasks these routines perform are quite diverse hence their own chapter 7 1 BYTE FUNC Rand purpose to generate a random number format BYTE FUNC Rand BYTE range parameterss range is the upper limit for th
129. k Hence this transcription It along with the ZoomText screen reader allow me to read this document Jim Patchell August 17 2012 THE ACTION SYSTEM PART I Introduction to ACTION 1 The ACTION System 2 How to Write and Run a Program PART Il The ACTION Editor Table of Contents Introduction The Editor Commands Atari ACTION Editor Technical Considerations AUN PART Ill The ACTION Monitor Table of Contents 1 Introduction 2 ACTION Monitor Commands 3 Program Debugging Facilities PART IV The ACTION Language Table of Contents Introduction ACTION Vocabulary Fundamental Data Types Expressions Statements Procedures and Functions Compiler Directives Extended Data Types Advanced Concepts OONDOOARWND PART V The ACTION Compiler Table of Contents Introduction Compiler Operation Using the Options Menu Technical Information AUN PART VI The ACTION Library Table Of Contents 1 Introduction 2 Output Routines 3 Input Routines File manipulation Routines Graphics and Game Controllers String Handling Conversion Miscellaneous Routines NOOA APPENDICES ACTION Language Syntax ACTION Memory Map Error Code Explanation Further Reading amp References Editor Commands Summary Monitor Commands Summary Options Menu Summary PRIMES Benchmark BASIC to ACTION Conversions TIO NMO OCOWD Part l Introduction to ACTION Welcome to ACTION We re here to introduc
130. k line in it lt and gt Whatever is between these two symbols is used to define some part of a format It is never a keyword and usually is a term describing what goes in its place in the construction e g lt Ildentifier gt means a valid identifier should be used and Whatever is between these is optional in the format construction lt identifier gt means that a valid identifier may be used here but is not required and As in music these symbols denote repetition Anything between them is repeatable from zero times on up e g I lt ldentifier gt means that you could have a list of zero or more identliflers here This symbol shows an or situation e g lt tdentifier gt lt address gt means you could use either an identifier or an address but not both Chapter 3 Fundamental Data Types Before discussing the Fundamental Data Types something must be said about variables and constants since they are the basic data objects the computer manipulates 3 1 Variables Legal variable names must be valid identifiers Other than this there is no restriction on variable names Because a working knowledge of functions and procedures is required before discussing the scope of a variable the topic is presented later in section 6 3 3 2 Constants There are three types of constants in ACTION numeric constants string constants and compiler constants Numeric constants may be entered in three
131. language command such as an assignment statement See section 5 1 2 is evaluated after you tell the ACTION Monitor to RUN your program when your program has control over what is being done Acompiler directive is evaluated when you tell the monitor to COMPILE your program so the compiler not your program has control The ramifications of this will soon become apparent 7 1 DEFINE The DEFINE directive is very similar to the editor s substitution lt CS gt S command except that it does the substitution at compile time To clarify this we first need to show the format DEFINE lt ident gt lt str const gt lt ident gt lt str const gt where lt ident gt is a valid identifier lt str const gt is a valid ACTION string constant That is with surrounding double quotes DEFINES are not really used in generating any object code when the program is compiled but are used to clarify ACTION source programs The compiler substitutes lt str const gt for lt ident gt every time lt ident gt is used in a program For example when you compile a program with the line DEFINE size 256 in it the compiler will replace every occurence of size with 256 This allows for some interesting options and problems if misused Since DEFINE will replace any string you can change the keywords themselves If you don t like the keyword CARD you could change it to say FROG with this command DEFINE FROG CARD Now whenever
132. late the hardware color registers In this way we can change the background color during one frame In fact we can do it 12 times and so get 12 colors in graphics 0 We have to make sure that we don t change colors in the middle of a scan line so we ll make use of the hardware variable WSYNC which tells when a scan line is done and the next one has not yet begun The variable VCOUNT tells how many scan lines have been put out and we use it to time the scrolling Example 1 PROC scrollcolors BYTE wsync 54282 the wait for sync flag vcount 54283 the scan line count flag clr 53272 shardware register for background ctr chgclr 0 a counter and a color changer incclr sincrements color luminance Graphics 0 set graphics 0 PutE FOR ctr 1 TO 23 print Out demo message DO PrintE A DEMO OF SHIFTING BACKGROUND COLORS OD Print A DEMO OF SHIFTING BACKGROUND COLORS DO Start of infinite scrolling loop FOR ctr l1TO 4 DO incclr chgclr set base color to Increment DO start of UNTIL loop wsync 0 _ waits for end of scan line clr incclr change displayed color incclr 1 change luminance UNTIL vcount amp 128 end of screen test OD end of UNTIL loop OD end of FOR loop chgclr l change the base color OD rend of infinite scrolling loop RETURN end of PROG scrollcolora 9 3 Addressing Routines The concept behind specifying the address of a routine is similar to that of specifying the address of a variable O
133. le value PrintE Welcome to the guessing game I m PrintE thinking of a number from 0 to 100 num Rand 101 gete the number to guess WHILE guess lt gt num DO start of WHILE loop Print What s your gueas guess InputB get user s guess IF guess lt nun THEN guess too low PrintE Too low try again ELSEIF guess gt num THEN guess too high PrintE Too high try again ELSE guess just right PrintE Congratulations PrintE You got it Fl end of guess testing OD end of WHILE loop RETURN end of PROC guesswblle Output 2 Welcome to the guessing game I m thinking of a number from 0 to 100 What s your guess 50 Too low try again What s your guess 60 Too highf try again What s your guess 55 Too low try again What s your guess 7 Congratulations You got it Notice how powerful manipulating conditionals like IF within a loop can be It allows the computer to take care of multiple possible outcomes every time it goes through the loop 5 2 4 3 UNTIL Statement In the last section we said that a WHILE loop could execute zero times because its conditional expression was evaluated before loop execution began The form of the UNTIL statement is such that this loop always executes at least once After you see the form you ll probably understand why this is so DO lt statement gt lt stetement gt UNTIL lt cond exp gt OD This looks like a common DO OD loop until you
134. les are assigned space according to the definition of the basic data types The following table should help your understanding of data allocation Data Type Allocated Comments BYTE 1 byte fundamental type CHAR 1 byte fundamental type CARD 2 byte fundamental type INT 2 byte fundamental type ARRAY fundamental type size extended type time the number of elements TYPE sum of sizes of extended type fundamental types as given in the declaration string all characters in the each string is allocated string plus a preceeding separately even if set byte to denote length equal to the same identifier 2 3 Routines The compiler allocates space for routines procedures and functions following that space allocated to the declared global variables The variables declared local to a given routine precede the executable language statements in that routine Program text statenents within procedures and or functions is evaluated and converted directly into machine code 2 4 INCLUDEd Programs Programs can be INCLUDEd at any place in the program Of course the INCLUDEd text must not conflict with the text currently being processed The things to watch out for are conflicting identifiers and out of context insertions When errors are detected in the INCLUDEd text they are usually displayed in the message area The error is always shown in the Monitor s command line and the bell sounds 2 5 Addit
135. lete text from the Editor buffer The seventh sections shows you how to undo certain deletions if you have made a mistake 2 5 1 Deleting a Character To delete the character under the cursor the one the cursor is flashing on top of press lt CTRL gt lt DELETE gt The characters to the right of the character just deleted will move left to fill the empty space left by the deleted character To delete the character to the left of the cursor press lt BACK S gt If you are in Replace mode this will replace the character to the left of the cursor with a space If you are in Insert mode this will delete the character to the left of the cursor and then move all the following characters over to fill the empty space 2 5 2 Inserting Changing a Character As mentioned in section 2 3 there are two different modes for text entry Replace mode and Insert mode When you first enter the ACTIOMI Editor it is in Replace mode To change from one mode to the other press lt CTRL gt lt SHIFT gt I Some of the Editor commands are mode dependent that is they operate differently depending on the text entry mode You can insert a blank character at the cursor position by entering lt CTRL gt lt INSERT gt The text from the cursor to the right end of the line moves right one space and a blank space is inserted at the cursor position NOTE if you are in Insert mode you can simply press the space bar 2 5 3 Line Deletions To delete
136. leted the entire block Move the cursor to the line above which you want the block to be pasted Now simply press lt CTRL gt lt SHTFTS gt P and the block will be pasted To copy a block of text use the same method as for moving a block but first paste the block back into its original position before moving to place where you want it copied Since pasting does not clear the copy buffer you can paste the same block or line in many different places thus allowing multiple copy s 2 8 Tags Tags allow you to mark any location in your text To set a tag at a given cursor position press lt CTRL gt lt SHIFT gt T The message area will display the prompt tag id Enter the one character identification you want for that tag and press lt RETURN gt If the id you give already has a tag associated with it the old tag will be lost and the id will refer to the new tag To move to a specified tag press lt CTRL gt lt SHIFT gt G The message area will display the prompt tag id Enter the id character of the tag you want to go to If the tag exists the cursor will be moved to it and the window will be moved to display the surrounding text If the tag doesn t exist the Editor will print tag not set in the message area This means that no tag with the given id character exists WARNING Any operation which alters the contents of the line character insertions deletions or changes line breaking or recombining clears the tag
137. lity For example if you pass a CARD when the procedure wants a BYTE the LSB of the CARD will be put into the BYTE variable and the procedure will carry on as though you had passed it a BYTE see Part IV for more info A Note On Parameter Variable Types All of the following are valid as parameters 1 Fundamental Data Type variables 2 Array Pointer and Record References 3 Array Pointer and Record Names In the third case the names are used as pointers to the first element the value or the first field in the named variable 6 5 MODULE MODULE is a very Simple directive It s form is MODULE It simply tells the compiler that you wish to declare some more global variables It is useful when you have vritten a large program in sections each with its own global variables If you say MODULE at the beginning of each section then the compiler will add all the global variables to the global variable table A program need not have a MODULE directive because the compiler assumes one MODULE directive at the beginning of the program whether you put it there or not The declaration of global variables must come either immediately after a MODULE or at the very beginning of the program which is really right after the MODULE assumed by the compiler Chapter 7 Compiler Directives Compiler directives are different from the standard language commands in that they are executed at compile time rather than run time A
138. mbol the ACTION compiler recognizes as something special whether it be an operator a data type name a statement or a compiler directive AND Fl OR UNTIL ARRAY FOR POINTER WHILE lt gt BYTE FUNC PROC XOR CARD IF RETURN gt CHAR INCLUDE RSH gt DEFINE INT SET d lt i DO LSH STEP lt ELSE MOD THEN amp ELSEIF MODULE TO ii EXIT OD TYPE WARNING You may not use the above keywords in an context other than the one defined in the ACTION Language specifically you may not use these words as identifiers 2 1 Special Notations When discussing the language we use some terms which might be unfamiliar to you so their meanings are presented here The list is in alphabetical order with the symbols at the end Address An address is a location in memory When you tell the computer to put something into memory you must give it an address just like you give the post office the address of the destination of a letter on the letter s front In the computer there are only house numbers no streets no cities no states and no zip codes So an address to the computer is simply a number Alphabetic Any letter of the alphabet in either upper ABC or lower abc case Alphanumeric includes the digits 0 through 9 as well Identifier Throughout the manual we will refer to the names you give to variables procedures etc as identifiers We d
139. me you used the command This information is called the default user response If the default user response you see in the message area is what you want you simply press lt RETURN gt This saves you time because you don t have to retype the same response many times If you don t want to use the default user response you have the ability to change either part or all of it 1 2 Editor Concepts and Features TEXT WINDOWS When you look at your TV or monitor screen imagine that you are looking through a window At any one time you can only see 23 lines of 38 characters each This seems very limiting and would be if you couldn t move the window around The ACTION Editor makes it possible for you to move this window around both horizontally and vertically so that you can look at your whole program But the Editor is even more sophisticated than that If you are looking through the window and you want to look at one line which extends beyond the bounds of the window you can move to that line and look at the whole thing The line will move to fit into the window but the window stays right where itwas When you move off that line it pops back into its proper place with respect to the window The Editor even allows you to split your screen into two windows each of which you can control separately This enables you to look at two different programs or different parts of the same program at the same time TEXT LINES The ACTION Editor
140. n RETURN seeker D match and return FI if found OD RETURN 0 no match found End of FUNC findmatch This function needs very little explanation since it s straightforward compared to the previous examples All we do is go to every record and test its idnum field for a match with testidnum Now let s turn the past two examples into a true program by putting a shell around it Example 4 MODULE declaring some global variables TYPE idinfo CARD idnum employee a I D number codenum his access code BYTE level his employment level name first letter of name BYTE ARRAY idarray 1000 enough space to hold 40 records DEFINE recordsize 25 nameoffset 5 CARD reccount 0 PROC fillinfo This is simply the modified version of the previous example idinfo POINTER newrecord BYTE POINTER nameptr _ pointer to name field BYTE continue DO newrecord idarray reccount recordsize Print D number newrecord idnum InputC get I D number OD Print Employment level A Z newrecord level GetD 7 employtnent level Print Access code newrecord codenum InputC get secret code nameptr newrecord nameoff set pointer nameptr to PrintE Employee s name start of name field Print form Last First InputS nameptr read name into name field reccount 1 PutE Print Input another record Y or N continue GetD 7 PutE UNTIL continue N OR contin
141. n a record nameptr newrecord nameoffset Here we are setting the value i e where we want the pointer to point of the pointer nameptr It s set by taking the address of the start of the record newrecord and adding the offset distance to the first byte of the string storage location InputS nameptr This is used to read in the name and uses nameptr as a pointer to the storage location just as shown in section 8 2 3 example 2 except that we are using a pointer instead of an array name which is just a pointer to the first element anyway Now that we have a way to put the records into the array we need a way to search through the array record by record when looking for a match The following is a function designed to do just that It will access the array as using the record format of example 2 and return the address of the start of the first record with an idnum matching the one passed in as a parameter If no match is found then 0 is returned as the address Note that this function uses variables declared in the global statement section i e after the MODULE of the previous example Example 3 CARD FUNC findmatch CARD testidnum idinfo POINTER seeker points to each record In turn to do test BYTE ctr used as a counter in the FOR loop FOR ctr 0 TO reccount 1 minus one because we DO start at 0 not 1 seeker idarray ctr recordsize index record IF seeker idnum testidnun THEN test for a
142. ndamental Data Types A 3 ACTION Program Structure ACTION Program A 4 Declarations System Declarations DEFINE Directive TYPE Declaration for records Variable Declarations Variable Declaration for Fundamental Data Types Variable Declaration for Pointers Variable Declaration for Arrays Variable Declaration for Records A 5 Variable References Memory References Fundamental Type Variable References Pointer Type Variable References Atray type Variable references Record Type Variable References A 6 ACTION Routines Routines Procedure Structure Function Structure Routine Calls Parameters A 7 statements Assignment statement EXIT statement IF statement DO OD Loop UNTIL statement WILE Loop FOR Loop Code Blocks A 8 Expressions Relational Expressions Arithmetic Expressions A 1 ACTION Constants Numeric Constant lt num const gt lt dec num gt lt hex num gt lt char gt lt dec num gt lt digit gt lt dec num gt lt digit gt lt hex num gt lt hex digit gt lt hex num gt lt hex digit gt lt hex digit gt lt digit gt A Il B I C I D E F lt dec digit gt 0 1 11 2 1 31 41 S 16171819 lt char gt lt any printable character gt String Constant lt str const gt lt string gt lt string gt lt str char gt lt string gt lt str char gt lt str char gt lt all possible characters except gt Compiler Constant lt comp
143. ng a memory value The SET command in the Monitor works exactly as in the Language itself so we will refer you there for a description of its usage See part IV section 7 3 2 9 WRITE Saving Compiled Programs You can write a compiled program called a binary file to disk for later execution directly from DOS by entering WRITE then in quotes a valid file specification The format is WRITE lt filespec gt lt RETURN gt The binary file in memory is saved to the specified file on the disk The file is created if necessary If there isn t sufficient room on the disk or the disk is write protected you are warned with an error message and can try again Examples WRITE PRIME BIN lt RETURN gt W D1 PRIME BIN lt RETURN gt save a compiled version of the PRIME program to disk 1 W C save the compiled program to cassette The OS or DOS command to execute a machine language program can be used to execute a program saved to by the W command See the references mentioned in Appendix D 2 10 XECUTE Immediate Commands You can execute any ACTION language command or any ACTION compiler directive except MODULE and SET from the ACTION Monitor Preface any such command with the command XECUTE then the statement s Press lt RETURN gt Examples XECUTE PrintE Hello World lt RETURN gt X trace 255 lt FETURN gt NOTE using this command is very similar to the BASIC direct mode 2 11 Displa
144. nly the reason behind the concept changes In the last section we talked about using Atari system registers directly by addressing an ACTION variable to the proper location Because you can define a routine s address you can make direct calls to OS and hardware routines directly and do your own manipulation of I O The method used will be discussed in the following section because this method applies to all machine language routines whether written by you resident on the OS or resident in the ROMs 9 4 Assembly Language and ACTION ACTION allows you to make calls to machine language routines very easily There are only two requirements You need to know the starting address of the routine The routine must end with an RTS if you want to get back to ACTION For assembly language programmers these are not difficult requirements to fill What about parameters Yes is the answer You can even send parameters to machine language routines The compiler stores parameters in this way Address nth byte of parameters A register 1st X register 2nd Y register 3rd A3 4th A4 oth SAF 16 th And now for an example PROC CIO E456 BIfTE areg xreg Declaring the OS procedure CIO xreg will contain the iocb number times 16 sand areg is a filler so the number won t go into register A CIO expects it In X reg PROC reatichannel2 This procedure will open channel
145. no commas between the different variable declarations between the CARD and BYTE declarations for example If you do put commas in the compiler will try to read the fundamental type words CARD BYTE INT as variables and that will cause a compiler error 8 3 1 2 Declaring Variables The last section showed you bow to declare a record type and this section will show you how to declare variables of a given record type The format is very similar to that used when declaring variables of fundamental types but it does have its peculiarities lt ident gt lt var gt lt addr gt lt var gt lt addr gt where lt ident gt is the name of the record type lt Var gt is a varible whose data type is declared to be the record type lt addr gt is the address you want the record located at Here s an example using the record type declared in the previous section After the example is an explanation of what s going on TYPE rec BYTE b1 b2 two BYTE fields first INT i1 then one INT field CARD c1 c2 c3 toen three CARD fields BYTE b3 sending with a BYTE rec arec declares arec as data type rec brec 8000 declares brec as type rec and places it at address 8000 EXPLANATION rec Shows that the following variables are of data type rec just as BYTE INT and CARD when used in variable declarations show that the following variables are of those types arec Declares arec to be a vari
146. ntered If you change the value of lt counter gt in the Ic op you will change the number of times the loop executes because lt counter gt is a variable in the loop It is variable in the loop because the FOR statement itself must change the value of lt counter gt every time it goes through the loop for increments lt counter gt by the STEP value Following is an example to illistrate changing lt initial value gt lt final Value gt and lt counter gt in the FOR loop itself Example 3 PROC changeloop BYTE ctr start 1 end 50 FOR ctr start TO end DO Start 100 doesn t affect number of repetitions End 10 doesn t affect number of repetitions PrintBE ctr Ctr 2 DOES affect number of repetitions OD RETURN Output 3 3 7 15 31 Below is a table to show what is going on each time through the Loop rep tells which repetition the loop is on inc ctr shows the result of the FOR loop incrementing the value of the counter Print shows what is printed out to the screen and ctr 2 shows how this assignment statement changes the value of the counter rep inc ctr Print ctr 2 1 1 2 2 3 3 6 3 7 7 14 4 15 15 30 5 31 31 62 After the fifth loop is through the counter equals 62 This is greater than lt final value gt 50 so the loop is exited after only 5 repetitions not 50 Manipulating the counter within its own loop can lead to very In
147. o i e into num Print num now equals PrintBE num shows that 255 really went into num Bptr 0 puts 0 into num Print num now equals PrintBE num shows that num equals 0 now Bptr chr makes bptr point to chr now Print bptr now points to address PrintF H bptr prints out chr s address so we PutE know that bptr really changed Bptr q puts q into the location bptr points to i e into chr Print chr now equals Put chr shows that chr really equals q PutE Bptr z changed chr to z Print chr now equals Put chr shows that chr is equal to z PutE RETURN Output 1 bptr now points to address E0 num now equals 255 num now equals 0 bptr now points to address E1 chr now equals q chr now equals z Notice that we use the operator when we want to put a value into the place the pointer points to So the line bptr 0 in the above example is the same as saying num 0 because bptr is pointing to num at that time Although we don t use it in the above example pointer references can be used in arithmetic expressions as follows X ptr Also notice that PrintF H bptr is valid What this means is that bptr can be accessed as a CARDinal number as well as an address This is useful when debugging your program because you can find out where the pointer is pointing easily 8 2 ARRAYS Arrays allow you to manipulate lists of var
148. o nothing After showing you some statements that do something and after stressing the necessity of statements that do something why is there a statement that does nothing There are actually a couple of good uses for a statement that does nothing Timing Loops and ELSEIF cases Since we haven t yet discussed loops at all we ll simply say that timing loops are used as a time delay e g if you want to pause between printing lines to the screen you just use a timing loop to waste a few moments You can find an example of a timing loop in section 5 2 4 1 To illustrate the use of the null statement in ELSEIF cases here is an example Scenario You are writing a program that allows stock brokers to find out information about certain stocks using the commands you have made available The commands you re implementing are BUY DOWN FIND QUIT SELL and UP but you haven t Implemented FIND yet All you do is test the first letter of the entered command so you have to test for B D F Q S and U But FIND isn t done so what do you do when they type F Easy you do nothing hoping that someday when FIND is ready you ll do something Here s how the program fragment might look IF chr B THEN dobuy ELSEIF chr D THEN dodown ELSEIF chr F THEN here s the null statement ELSEIF chr Q THEN doquit ELSEIF chr S THEN dosellt ELSEIF Chr U THEN doup ELSE doerror no command match FI All the do s are
149. o return the current file sector and byte offset within that sector on a specified disk drive format PROC Note BYTE chan CARD POINTER sector BYTE POINTER Offset parameters chan is a valid channel number 0 7 sector is a pointer to the sector number variable offset is a pointer to the byte offset variable description This procedure returns the disk sector and byte offset within that sector of the next byte to be read or written i e it returns the value of the disk file pointer 4 5 PROC Point purpose to set the disk file pointer Sector and byte offset to allow random file access format PROC Point BYTE chan CARD sector BYTE offset parameters chan is a valid channel number 0 7 sector is a valid sector number 1 720 offset is the byte offset within that sector description This procedure allows you to set the disk file pointer to any location within a disk file thus enabling random access of information NOTE the disk file must have been Opened mode 12 update for the Point routine to work Chapter 5 Graphics and Game Controllers The ACTION Library contains quite a few routines designed specifically to make game writing using visual and sound effects easy and quick At your fingertips you have the ability to manipulate bit map graphics i e the BASIC graphics modes the myriad of sounds available on the ATARI and get information about the game controllers both paddle and joystick Since
150. o the nested statements The compiler avoids any confusion by IF Fl pairing A FI is paired to the first preceding IF that doesn t already have a FI paired to it For example IF lt expA gt THEN IF lt expB gt THEN lt statement9 gt ELSEIF lt expC gt THEN ELSEIF of IF lt expB gt IF lt expD gt THEN lt statements gt ELSE else of IF lt expD gt lt stateinents gt FI end of IF lt expD gt FI of IF lt expB gt ELSEIF lt expE gt THEN ELSEIF of IF lt expA gt lt tateinents gt ELSE else of IP lt expA gt lt statements gt FI Fl of IF lt expA gt The dashed lines show the IF FI pairings the comments show which IF statement a particular Fl or ELSEIF pertains to and the indentation shows a change of nexting levels The following program example contains nested FORs This one even does something worthwhile it prints out the multiplication table up to ten times ten PROC timestable This procedure prints out the moltlplication table up to 10 times 10 BYTE c1 counter for outer FOR loop c2 counter for inner FOR loop FOR Ci 1 TO 10 outer loop control DO _ start of outer loop IF c1 lt 10 THEN single digits need a space Print before them in the first column FI PrintB c1 print 1st number in column FOR c2 2 TO 10 inner loop control DO start of inner loop IF c1 c2 lt 10 THEN single digits n
151. o this because names in ACTION must follow some guidelines 1 They must start with an alphabetic character 2 The rest of the characters must be alphanumeric or the underline _ character They may not be keywords These rules must be obeyed when you wish to create an identifier otherwise you will get a syntax error MSB LSB MSB stands for Most Significant Byte and LSB stands for Least Significant Byte In the decimal system we have significant digits not bytes For example the most significant digit of 54 is 5 and the least significant is 4 If you are un familiar with the byte storage system don t worry You can program very well in ACTION without knowing anything about the internal workings of the computer Note that two byte numbers stored and used by ACTION are generally in LSB MSB order as is conventional on 6502 based machines The dollar sign when used In front of a number tells the computer that the number is hexadecimal the base 16 number system useful when working directly with the computer not the customary decimal Examples 24fC 0D 86 FO000 The semicolon is the comment symbol and everything on a line after it is ignored by the compiler Examples This ls a comment This is not and will cause a compiler error This comment has a semi colon in it var 3 comments can come after executable statements this is a 3 line comment with a blan
152. on This routine allows you to set the color of a specific color register and so manipulate the colors displayed in a given mode The following tables give some information pertinent to the usage of this procedure Set Color hue Color Set Color Hue Color number number 0 Gray 8 Blue 1 Gold 9 Light Blue 2 Orange 10 Turquoise 3 Red Orange 11 Green Blue 4 Pink 12 Green 5 Purple 13 Yellow Green 6 Purple Blue 14 Orange Green 7 Blue 15 Light Orange The above table shows the 16 hues available on the ATARI and their numeric code for use as the hue parameter of the SetColor procedure Register Default Color Default Color Luminance 0 2 8 Orange 1 12 10 Green 2 9 4 Dark Blue 3 4 6 Pink or Red 4 0 0 Black This table shows which colors are the defaults used when you don t specify your own color for a given SetColor register NOTE Colors may vary depending upon the television or monitor type condition and adjustment The luminance value a measure of the brightness of a color ranges between 0 and 15 where 0 is darkest and 15 is brightest 5 3 BYTE color color isn t a library routine but a variable defined in the library for use with the Plot DrawTo and Fill library procedures After you pick your graphics mode using Graphics and set up the color registers using SetColor you can plot and draw in tha
153. opy buffer for text copy move processing See lt CTRL gt lt SHIFT gt P description and section 2 7 lt BACK S gt If in Replace mode see lt CTRL gt lt SHIFT gt 1 then this replaces the character to the left of the cursor with a space In Insert mode this removes the character to the left of the cursor and scrolls the rest of the line left to fill the empty space lt CTRL gt lt right arrow gt This moves the cursor right one character stopping at the end of the line Upon encountering the right margin of the window the editor keeps the cursor within the display by scrolling the line contents to the left one character lt CTRL gt lt left arrow gt This moves the cursor left one character at a time stopping at the beginning of the line When at the left margin of the window but not yet at the Left end of the line the editor keeps the cursor within the display by scrolling the line contents right one character 3 3 Commands Unique to the ACTION Editor lt CTRL gt lt SHIPT gt D This deletes the current window from the screen The window contents are cleared from memory and the window itself disappears from the screen lt CTRL gt lt SHIFT gt F This finds a specified group of alphanumeric characters in text If the character string is found the cursor and window are moved to display it lt CTRL gt lt SHIFT gt G This finds a user specified tag anywhere in file from any starting location If found the surr
154. ore parameters than the procedure declaration but it may have fewer See section 6 4 for a discussion of parameters 6 2 FUNCtions As mentioned in the overview of procedures and functions the fundamental difference between the two is that functions return a value This makes the way in which they are declared and called somewhat different from procedure declarations and calls Since functions return a numeric value they must be used where a number is valid e g in arithmetic expressions 6 2 1 FUNC Declaration Declaring a function is similar to declaring a procedure except that you must be able to show both what type of number the function returns BYTE CARD or INT and what that number is The format is lt type gt FUNC lt identifier gt lt addr gt lt parameter list gt lt variable decl gt lt statement list gt RETURN lt arith exp gt where lt type gt is the fundamental data type of the value the function returns FUNC is the keyword denoting a function declaration lt identifier gt is the name of the function lt addr gt optionally specifies the starting address of the function see 9 3 lt parameter list gt is the list of parameters required by the function see section 6 4 for an explanation of parameters lt variable decl gt is the list of variables declared local to this function see section 3 4 1 for variable declaration and 6 3 for scope of v
155. oubt on my part the best compiler that was ever written for the 6502 as it was tailored to what that processor was capable of doing Preface by the Editor This was a work of love for me bought the ACTION Compiler when it first came out however it was about a year before actually used it And when did use it was sorry had waited My first foray into High Level Programming Languages on the Atari Computer was FORTH I Know for some that what am about to say is heresy but was just never able to get the hang of it This is probably more likely due to my lack of exposure to structured programming did not have that problem with ACTION ACTION Was the very first structured language had ever used Up to that point BASIC and FORTRAN were the only high level languages used but if was serious about the code used assembly ACTIOON gave me enough of a leg up that when got a job that required program in PL M I was right at home do not Know Clinton Parker and I wish I did have been in contact with him and he was gracious enough to allow me to publish this document The main reason did this transcription was because had always wanted to write a compiler and ACTION was the first one attempted to duplicate At that time did not have at my disposal the software tools that make doing such a job a lot easier When I became disabled due to blindness decided would do my darnedest to accomplish that tas
156. ounding text is displayed and the cursor is positioned at the tag lt CTRL gt lt SHIFT gt H Moves cursor to the beginning of the file home lt CTRL gt lt SHIFT gt I Alternates between the character Replace and the character Insert modes the editor starts out in replace mode The mode being switched to Is shown in the message area This command affects lt BACK S gt and lt RETURN gt handling lt CTRL gt lt SHIFT gt M Goes to the ACTION Monitor Part III lt CTRL gt lt SHIFT gt P After one or more lines are loaded into the copy buffer using lt SHIFT gt lt DELETEs the cursor can be moved anyplace in the text Pressing lt CTRL gt lt SHIFT gt P causes the lines in the copy buffer to be pasted at the current cursor location Succeeding text with tags is moved down lt CTRL gt lt SHIFT gt R This command Reads a file from a peripheral storage device The file name given must be compatible with the DOS you are using If no device is specified in the file name D1 is assumed lt CTRL gt lt SHIFT gt S This command does String Substitution This coimnand allows you to substitute a new string of up to 32 characters for an old one Can also be used successively to substitute multiple occurrences of the old string lt CTRL gt lt SHIFT gt T This command Sets a tag The position of the cursor in the text is marked invisibly by a one character alpha numeric tag assigned to that location lt CTRL gt lt
157. out by a special program called a compiler before the actual execution of your program This requires an intermediate step between your entry of the program and its execution by the computer The step is technically known as the compile During the compile the ACTION compiler analyzes your program on a line by line basis Your program is converted into a different language called machine language with storage for both global and local variables The converted program can then be executed by your Atari running at a speed much greater than that of the interpreted Atari BASIC 1 1 VOCABULARY This chapter refers to several terms which you first learned about in Part IV Those terms are listed here with each term briefly defined term comments lt ident gt any valid identifier lt value gt any valid hex or decimal value lt compiler constant gt evaluates lt ident gt s address lt address gt memory location 1 2 Compiler Directives The compiler directives are discussed in depth in part IV chapter 7 and little more need be added here We simply remind you that the compiler directives are executed at compile time not run time so do not use them when you want to change an operational parameter while your program is running Chapter 2 Compiler Operation Allocating Space In this chapter we ll discuss how the the ACTION Compiler allocates memory space for your compiled program its variables its rout
158. p with a hopefully positive number at the end This number is returned and can be used to do other things like determine the size of your next check If we wanted to make Doing the dishes a function we could change the statement to the question Do the dishes need doing hoping that the person would answer the question and then do the dishes if required This would get the dishes done like the procedure but also return a value whether the dishes needed doing in the first place and thus make it a function NOTE Throughout the rest of this manual we will use the word routine instead of saying procedure or function Doing this makes the concepts easier to follow When you see procedure or function it means the concept or idea being discussed is specific to that class of routines and not applicable to both classes 6 1 PROCedures Procedures are used to group some statements which accomplish a task into a named block that can be called on to do this task To utilize procedures in ACTION you must learn how to do two things 1 declare procedures 2 call procedures The following three sections will show you how to do the above and give some examples to let you see procedures in ACTION small pun intended 6 1 1 PROC Declaration The ACTION keyword PROC is used to denote the start of a PROCedure declarationt PROCedure construction looks quite like a group of statements with a name and some other Information
159. pherals You must set up one of the IOCBs so that it will handle the peripheral you want it to This ie done using the Library routine Open and so is not a difficult task to accomplish When you see the term default channel it refers to the OCB ACTION sets up and uses for screen display purposes This means that routines which do I O using default channel will get and put information from and to the screen device E NOTE the default channel is channel 0 NOTE for more information on IOCBs see your Operating System reference manual 1 2 Library Format The library routines are presented in a manner which makes it very easy to understand how to use and call them To show you what we mean lets take one of the routines and explain what information each part of the presentation format can tell you The routine we ll look at is Locate Example 5 8 BYTE FUNC Locate purpose determine the color or character at a given screen location format BYTE FUNC Locate CARD col BYTE row parameters col is a column number valid in the current graphics mode row is arow number valid in the current graphics mode description This routine retrieves the ATASCII code of the character or the number of the color at the specified location The registers this routine uses are incremented so as to point to the adjacent horizontal position the first position in the next line if you located the last position on a line All of the Get
160. procedures to do the given command If you look at the case of chr F you see that nothing is done That s the null statement When FIND is ready all you need to do is put the dofind procedure in Where the null statement now is and you ll have it in the look up table and ready for use 5 2 3 Loops Loops are used to repeat things specifically statements If for some strange reason you wanted to fill the screen with stars you could either send out each star with a separate statement or you could use a loop to do this for you All you need to do is tell the loop how many times you want it to put out a single star and it will do it if you use the proper statement format of course There are two ways to tell a loop how many times you want it to do something You can give it an explicit number or you can give it a conditional expression and execute the loop depending on the outcome of that expression The FOR statement uses the first method and both WHILE and UNTIL use the second What happens when you don t tell the loop how many times it should execute What happens when the conditional expression never evaluates to a value that will stop the loop You get what is known as an Infinite Loop There is only one way to get out of an infinite loop you have to push the lt SYSTEM RESET gt key ACTION approaches loops in the following manner There is a basic loop which when used alone is infinite Then there are
161. ray This process will continue as long as the user desires sto input more information idinfo POINTER newrecord BYTE continue DO newrecord idarray reccount recordiize Print D number newrecord idnum InputC jget D number Print Employment level A Z newrecord level GetD 7 employment level Print Access code newrecord codenum InputC get secret code recount 1 PutE Print Input another record Y or N continue GetD 7 PutE UNTIL continue N OR continue n OD RETURN PROGRAMMING NOTE This procedure does not make sure you re within the bounds of the array nor does ACTION itself so you might want to add a boundary checking routine EXAMPLE 1 NOTES There are a couple things this procedure does that require a detailed explanation including these procedure lines DEFINE recordsize 5 idinfo POINTER newrecord newrecord idarray reccount recordsize newrecord XXX Xxx reccount 1 We ll go through these one by one This should not only explain the statements themselves but should also clarify the concept we re using to accomplish the array of records DEFINE recordsize 5 This DEFINE is used as the jump size when we are going through the array The record type idinfo is 5 bytes long 2 CARDS and 1 BYTE so this will allow us to go through the array in 5 byte leaps Every time we leap like this we will skip over one record thus eliminating the possibility of wri
162. rig purpose to determine whether a paddle trigger has been pressed format BYTE FUNC PTrig BYTE port parameters port is the port number 0 7 of the desired paddle description This function returns the current value of the given paddle s trigger A value of 0 is returned if the trigger is pressed otherwise the value returned is non zero 5 13 BYTE FUNC Stick purpose to return the current numeric value of a specified joystick format BYTE FUNC Stick BYTE port parameters port is the port number 0 3 of the desired joystick Description This function returns the current position of the joystick using codes as in the following diagram 5 14 BYTE FUNC STrig purpose to determine whether a joystick trigger has been pressed format BYTE FUNC STrig BYTE port parameters port is the port number 0 3 of the desired joystick description This function returns the current value of the given joystick s trigger A value of 0 is returned if the trigger is pressed otherwise the value returned is non zero Chapter 6 String Handling Conversion The routines discussed in this chapter allow you to manipulate strings change a number to a string and change a string into a number No further discussion is necessary since the routine descriptions speak for themselves 6 1 String Handling Routines The following four routines make possible some advanced string manipulation including string comparison string copying an
163. s IF WHILE UNTIL There may be only one relational operator in a simple relational expression so tests for multiple conditions must be handled differently They are covered in the following section on complex relational expressions The form of a simple relational expression is lt arith expxr gt lt rel operator gt lt arith exp gt where lt arith exp gt is an arithmetic expression lt rel operator gt is a relational operator Here are some samples of valid relational expressions cat lt 22A7 Var lt gt y 5932 counter 5 amp 7 e gt 3 Ccat dog addr SPF ptr offset lt gt SFO3D ptr amp offset 5 4 9 gt ctr 1 4 4 Complex Relational Expressions Complex relational expressions allow you to cover a wider range of tests by including multiple tests If you want to do something only on Sundays in July how do you get the computer to test whether it s Sunday and then test whether it s July ACTION allows you to do this kind of multiple testing with the AND and OR operators remember how they were glossed over in section 4 1 37 The compiler treats these as special relational operators to test a condition using simple relational expressions The form is lt rel exp gt lt sp op gt lt rel exp gt lt sp op gt lt rel exp gt where lt rel exp gt is a simple relational expression lt Sp op gt is one of the special operators AND or OR NOTE there are no exceptions to this form If you try something els
164. s a list of those ACTION supports each followed by it s meaning unary minus the negative sign Example 5 multiplication Example 4 3 integer division Example 13 5 this equals 2 since the remainder is dropped MOD remainder of integer division Example 13 MOD 5 this equals 3 since 13 5 2 with a remainder of 3 addition Example 4 3 subtraction Example 4 3 Notice that is not an arithmetic operator It is used only in relational expressions certain declarations and assignment statements 4 1 2 Bit wise Operators Bit wise operators manipulate numbers in their binary form This means that you can do operations similar to those the computer does since it always works with binary numbers The following list summarizes the operators amp bit wise and _ bit wise or l bit wise exclusive or XOR same as LSH left shift RSH right shift address of The first three compare numbers bit by bit and return a result dependent on the operator as seen below Table 1 Bit Wise AND amp compare the Bit A Bit B Result two bits returning 0 0 0 a value based on 0 1 0 this table 1 0 0 1 1 1 Example 5 amp 39 00000101 equals 5 decinial 00100111 equalH 39 decimal 00000101 result of amp is 5 Table 2 Bit Wise OR returns a value Bit A Bit B Result dependent on 0 0 0 this table 0 1 1 0 1 1 e
165. s a counter in loops WHILE UNTIL FOR program speed will increase because it s easier for the computer to manipulate one byte than many Also since characters are represented inside the computer as one byte numbers BYTE is also useful as a character type In fact the ACTION compiler allows you to use the keywords BYTE and CHAR interchangeably so those of you with PASCAL or C experience can use CHAR when dealing with characters and feel more at home 3 3 2 CARDinal The CARD type is very similar to the BYTE type except that It handles much larger numbers This is because it is internally represented as a two byte unsigned number Hence its values range from 0 to 65 535 TECHNICAL NOTE a CARD is stored in the LSB MSB form which is standard on 6502 based machines 3 3 3 INTeger This type is like BYTE and CARD in that it is integer only and can be entered in numeric format but that is where the similarity ends INT allows both positive and negative numbers ranging from 32768 to 32767 Itis internally represented as a two byte signed number TECHNICAL NOTE INTs are Stored LSB MSB like CARDS 3 4 Declarations Declarations are used to let the computer know that you wish to define something For example if you want the variable cost to be of the type CARD somehow you have to tell this to the computer Otherwise the computer won t know what to do when it sees cost Every identifier you use must be declared before i
166. s in the line HINT if you use the digits 0 9 as tag ids you are more likely to remember the id character Chapter 3 Comparing ACTION and ATARI Editors 3 1 Identical Commands lt SHIFT gt Used in conjunction with letter keys to change the caee of the letters or used to enter either an alternate character or command Hold the lt SHIFT gt key down while pressing the following key in the sequence e g lt SHIFT gt _ symbolizing the underline character _ means that you should hold the lt SHIFT gt key down while pressing the _ key lt CTRL gt Used in conjunction with one or more other keys to communicate a command or special character to the editor Hold the key down while pressing the following key in the sequence e g lt CTRL gt lt up arrows symbolizing the command to move the cursor up one line means that you should hold the lt CTRL gt key down while pressing the lt up arrow gt key lt Atari gt Display succeeding characters in inverse video Press key a second time to return to normal video display of entered characters lt ESC gt Allows the following control character to be entered as text lt LOWR gt Shift letter entry to lower case like unlocking the shift lock on a regular typewriter lt SHIFT gt lt CAPS gt Shift letter entry to upper case letters only like pressing shift and shift lock keys simultaneously on a regular typewriter lt SHIFT gt lt INSERT gt Inserts
167. s usable during program execution with certain restrictions The lt BREAK gt key will stop program execution only if you are 1 doing some sort of I O 2 calling a routine with more than 3 parameters These might seem strange circumstances but there is a good reason for them The ACTION System itself does not check to see if the lt RREAK gt key has been pressed during program execution but the system does make calls to CIO in the above two circumstances and CIO checks to see if the lt BREAK gt key has been pressed Library PROC Break If you want program execution to stop at any given place simply make a call to this Library routine at that point This routine acts exactly like the lt BREAK gt key except that it works under all circumstances Using this method to stop a program is more reliable than pressing lt BREAK gt because you know exactly where you are in the program when the program stop occurs NOTE you may use this routine more than once in one program if you want to break execution at more than one place Now that you have stopped the program you can use the Monitor commands and to look at the value of the variables you re using If this method of debugging is used with the Trace option on you can even find out where you are in your program if you are using the Library break you already know where you are and so look at the variables local to the procedure you re in as well as the global ones
168. se OR XOR Bitwise Exclusive OR According to this table our earlier example 4 5 3 would be evaluated as 4 5 3 because the is of higher precedence than the What if 4 5 3 were intended You d have to include the parentheses as shown to override the normal operator precedence Here are some examples to look over Table 8 Examples of operator precedence Expression Result Evaluation order 4 2 3 6 i 5 lt 7 True lt 43 MOD7 2 19 21 MOD 4 2 3 2 h 4 2 Arithmetic Expressions An arithmetic expression consists of a group of numerical constants variables and operators ordered in such a way that there is a numerical result The order is as follows lt operand gt lt operator gt lt operand gt Where lt operand gt is a numeric constant numeric variable FUNCtion call see section 6 2 3 or another arithmetic expression The first three possibilities are straightforward enough but the last one is a problem Here s an example to show you what we mean starting expression 3 4 22 7 2 Order Expression Evaluation Simplified expr Start 3 4 22 7 2 H 1 22 7 3 3 44 3 2 2 22 7 2 6 3 4 6 3 4 22 7 2 10 3 10 4 3 44 22 7 2 30 30 order is the order of the expression evaluation expression shows which expression is being evaluated evaluation shows the evaluation of th
169. sed in conjunction with the structured IF statement 5 2 4 Loop Controls ACTION has three structured statements that control the basic DO OD loop 1 FOR 2 WHILE 3 UNTIL By saying that they control the basic DO OD loop we mean that they limit the number of times the infinite loop executes thus making it a finite loop Controllable loops are one of the devices that make computers very useful If someone told you to write I ll never throw spitwads again one thousand times you would call that punishment but if you told the computer to do tbe same thing with a controlled loop of course it would think that the task was easy and mundane Now we ll take a look at each loop controlling statement in depth and then go into a property of all ACTION structured statements nesting 5 2 4 1 FOR Statement The FOR statement is used to repeat a loop a given number of times It requires its own special variable commonly called a counter In the examples the counter will be called ctr to remind you of this but you could call it anything you like The format of the FOR statement is FOR lt counter gt lt initial valued gt TO lt final value gt STEP lt inc gt lt DO OD loop gt where lt counter gt is the variable used to keep track of the number of times the loop has executed lt initial value gt ia the starting value of the counter lt final value gt is the ending value of the counter lt inc gt is t
170. sing the options menu to turn off the screen display during both disk I O and program compilation Simply press N lt RETURNS gt to the Screen prompt in the options menu NOTE this also turns off the screen for other ACTION system functions so you should turn t he display back on after you have finished compiling Turning the bell off When you are debugging a new program and have lots of errors such as typographical errors you might want to turn the bell off Simply press N lt RETURNS to the Bell prompt in the options menu Making the Compiler case sensitive Sometimes particularly as you get more sophisticated in your programming style you might desire that the compiler help you in your programming by reminding you whenever you forget to enter an ACTION key word in uppercase You also might wish to benefit from the increased flexibility of using different or mixed cases in your identifiers You can do both by pressing Y lt RETURN3 gt to the options menu prompt Case sensitive Use of this option is not necessary to successful ACTION programming However it is useful as an aid to documentation and in providing a much greater diversity in identifiers Listing the compiled code You can command the Compiler to list each program line as it is evaluated This may seem unnecessary because most errors which occur are noted and displayed on the screen during the compiling process However you might have
171. some loop controlling statements FOR WHILE UNTIL which limit the number of times this infinite loop executes We ll follow the same pattern first a discussion about the basic loop structure followed by an in depth look at the loop controlling statements 5 2 3 1 DO and OD DO and OD are used to mark the beginning and end respectively of the basic loop Everything between them is considered to be part of that loop As mentioned above a loop alone i e without any loop controlling statement is an infinite loop and you must force a break out of it Following ia a program example to illustrate the DO OD loop Don t worry about the PROC and RETURN statements they re just there so that the program will compile and run properly and will be discussed In full in the procedures and functions chapter 6 Example 1 PROC timestwo CARD i 0 j DO start of DO OD loop l 1 add 1 to i J i 2 set j equal to i 2 PrinteC i See the following Print times 2 equals PROGRAMMING NOTE for PrintCE j an explanation OD send of DO OD loop RETURN PROGRAMMING NOTE the mixed case words PrintC Print PrintCE you see in the example above are ACTION library functions and procedures You may learn more about them although their jobs here are fairly obvious in Part VI The ACTION Library You will see library routines used throughout the rest of this chapter so don t be alarmed they re only there
172. st new string you used following the prompt If you want to keep this new string simply press lt RETURN gt If you want a different new string type it in and press lt RETURN gt If this is the first time you are using Substitute you will see nothing following the prompt and you should type in the new string you want and press lt RETURN gt After you press the lt RETURN3 gt the message area will prompt you with for You will see the last old string you used following this prompt if you have used the Substitute before If you want to keep this old string simply press lt RETURNS gt If you want a different old string type it in and then press lt RETURN gt If this is the first time you are using Substitute you will see nothing following the prompt and you should type in the old string you want changed and press lt RETURN gt After you press this second lt RETURNs the Editor will try and do the substitution If it can t find the old string you ve given the message area will show the following not found If you press lt CTRL gt lt SHIFT gt S again before you do any other editing the Editor will execute the same substitution again This enables you to substitute more than one occurrence of the old string with the new one without having to keep responding to the Substitute and for prompts HINT you can delete the next occurrence of a string by using this ommand with the new string
173. string for the copy start is the starting point in lt dest gt for the copy stop is the stopping point in lt dest gt for the copy If stop is greater than the length of lt lt dest gt then the length of lt dest gt is changed to stop description This procedure is used to copy one string lt source gt into part of another lt dest gt lt source gt will be copied starting at element start of lt dest gt and the copying will stop at element stop of lt dest gt If the space allowed stop start 1 in lt dest gt is greater than the length of lt source gt then stop will be changed to make the space available and the length equal The copying this procedure does will overwrite the old elements of lt dest gt as it puts in lt source gt 6 2 Number to String Conversions The following three procedures convert the number given as a parameter into a character string There is one procedure for each of the numeric data types purpose to change a number into a character string format PROC StrB BYTE number lt string gt PRCC StrC CARD number lt string gt PROC Strl INT number lt string gt parameters number is an arithmetic expression remember that arithmetic expressions can simply be a constant or variable name lt string gt is the identifier of a CHAR ARRAY description These procedures turn BYTE CARD or INT values into character strings composed of the digits of the g
174. t The above is only the basic format The IF statement has two options ELSE and ELSEIF English also has these options so we ll use comparative examples If have 9 or more I ll buy the steak otherwise lII buy the fish platter The ACTION equivalent of this is IF money gt 9 THEN buy steak money ELSE Buy fish money Fl ELSEIF is somewhat different If have 9 or more I ll buy the steak If have between 8 and 9 I ll buy the fried fish If have between 6 and 8 I ll buy the chicken Otherwise I ll buy the hotdog would be IF money gt 9 THEN Buy steak money ELSEIF money gt 8 THEN Buy fish money ELSEIF money gt 6 THEN buy chicken money ELSE buy hotdog money Fl in ACTION Notice that we don t have to check for money gt 8 AND money lt 9 as in English We can do this because the computer goes through the list sequentially from top to bottom If any conditional case is true the statements it controls are executed and then the whole rest of the IF statement including all following ELSEIF and ELSEs is skipped So if the computer does get to money gt 8 we already know that we have less than 9 because the proceeding conditional tested for money gt 9 and found that condition false The ELSEIF option is very useful when you want to test a variable for a number of different conditions each requiring a different action 5 2 2 Null Statement The null statement is used to d
175. t is used whether it s a variable procedure or function name Variable declarations will be explained here followed by a note about numeric constant declarations procedure and function declarations are explained in chapter 6 3 4 1 Variable Declaration The procedure for declaring a variable is the same no matter what fundamental type you want it to be The basic format is lt type gt lt ident gt lt inlt info gt lt ident gt lt init info gt where lt type gt is the fundamental type of the variable s being declared lt ident gt is an identifier naming the variable lt init Info gt allows you to initialize the value of the variable or define the memory location of that variable lt init info gt has the form lt addr gt lt value gt Where lt addr gt is the address of the variable and must be a compiler constant lt value gt is the initial value of that variable and must be a numeric constant NOTE an explanation of lt gt and can be found in the vocabulary chapter 2 Notice that you can optionally have more than one variable declared by one lt type gt You can also optionally tell the compiler where you want each variable to reside in memory or initialize the variable to a value The following examples should help clarify this format BYTE top hat declare top and hat as BYTE variables INT num 0 declare num as an INT variable and initialize it to 0
176. t mode using any of the colors you ve specified by first using the assignment color lt number gt where lt numbers is related to the color register containing the color you want to use The following table shows this relationship for the different graphics modes For every group of related modes each SetColor register is followed by its associated color lt number gt and some descriptive comments Graphics SetColor Color Description and Comments Mode register number 0 0 N A and 1 N A all 2 N A Character Lumance text 3 N A Background windows 4 N A Boarder 0 N A Character 1 N A Character 1 2 2 N A Character 3 N A Character 4 N A Background 0 1 Graphics Point 1 2 Graphics Point 3 5 7 2 3 Graphics Point 3 ae Za 4 0 Gr Pt Background Boarder 0 1 Graphics Point 1 fe ze 4 6 2 3 a 4 0 Gr Pt Boarder Background 0 7 on 1 1 Graphics Point Luminance 8 2 0 Graphics point Background 3 oe se 4 Border 5 4 PROC Plot purpose to position the cursor at a specified location and then display a color using the library variable Color format PROC Plot CARD col BYTE row parameters col row is the horizontal colum number of the point being plotted is the vertical row number of the point being plotted description This procedure is used in graphics modes 3 8 to plot a point on the screen The size of the point displ
177. t rec name gt lt identifier gt lt field init gt lt fund var decl gt Variable Declarations lt var decl gt lt var decl gt lt base var decl gt lt base var decl gt lt base var decl gt lt fund decl gt lt POINTER decl gt lt ARRAY decl gt lt record decl gt Variable Declaration for Fundamental Data Types lt fund cecl gt lt fund type gt lt fund ident list gt lt fund type gt CARD CHAR BYTE INT lt fund ident list gt lt fund ident gt lt fund ident list gt lt fund ident gt lt fund ident gt lt identifier gt lt init opts gt lt init opts gt lt addr gt lt value gt lt addr gt lt comp const gt lt value gt lt num const gt Variable Declaration for Pointers lt POINTER decl gt lt ptr type gt POINTER lt ptr ident list gt lt ptr type gt lt fund type gt lt rec name gt lt ptr ident list gt lt ptr ident gt lt ptr ident list gt lt ptr ident gt lt ptr ident gt lt identifier gt lt value gt Variable Declarations for Arrays lt ARRAY decl gt lt fund type gt ARRAY lt arr ident list gt lt arr ident list gt lt arr ident gt lt arr ident list gt lt arr ident gt lt arr ident gt lt identifier gt lt dim gt lt array init opts gt lt dim gt lt num const gt lt arr init opts gt lt addr gt
178. t the end 2 1 5 PROC PrintF Formatted Output The PrintF procedure allows you to output numbers and strings on the same line through the use of a format control string This string tells the procedures exactly how you want the output to look purpose formatted output of data format Pr intF lt control string gt lt data gt lt data gt arguments lt control string gt the control string is made up of format controls and string text The text is output directly and the controls maximum of 5 give information for outputting the lt data gt parameters given lt data gt is an arithmetic expression which will be formatted according to its format control The first control tells how to output the first lt data gt the second control tells how to output the second lt data gt and so on description This is a sophisticated procedure enabling you to output formatted data to the default channel Up to five different data elements can be interspersed into a string each with its own output format The format controls are as follows lt control gt formatted data type S output data as a string l output data as an INT U output data as an Unsigned CARD oC output data as a CHARacter oH output data in unsigned hexadecimal P output the character E output an EOL lt RETURNS gt Notice that two of the controls E and do not manipulate or require data elements Th
179. teresting results some of which night even be useful As promised in section 5 2 2 here s an example of a timing loop BYTE ctr FOR ctr 1 TO 250 DO here s the null statement OD This is just used as a time waster something you ll use a lot if you re writing games or other programs which involve careful timing PROGRAMMING NOTE If you write a FOR loop which continues to the limit of the data type of the counter e g FOR ctr 0 TO 255 if ctr is a BYTE or FOR ctr 0 TO 65535 if ctr is a CARD the loop will be infinite because the counter can t be Incremented to a value greater the the given lt final value gt 5 2 4 2 WHILE Statement The WHILE statement and the UNTIL statement for that matter is used when you don t want to execute a loop a predetermined number of times WHILE allows you to keep looping as long as a given conditional expression is true It has the form WHILE lt cond exp gt lt DO OD loop gt where lt cond exp gt is the controlling conditional expression lt DO OD loop gt is a DO OD infinite loop Since the evaluation of the conditional expression is done at the start of the loop lt DO OD loop gt might not be executed at all This is not the case with UNTIL as you will see later Program examples using WHILE start on the following page Example 1 PROC factorials This procedure will print out the factorials up to some specified number the variable
180. the cursor to the end of the line and displays that end of the line If the line is longer than 36 characters then the cursor moves to the end of the line and the line is displayed so that only the rightmost 38 characters show lt CTRL gt lt SHIFT gt lt Moves cursor to beginning of line and displays the beginning of the line If the line is longer than 38 characters then the cursor moves to the beginning of the line and the line is displayed so that only the leftmost 38 characters show lt CTRL gt lt SHIFT gt lt BACK S gt At the beginning of a line this command deletes the otherwise invisible and inaccessible lt RETURN gt EOL The lower line is appended to the end of the preceding line The succeeding lines are moved up one line as needed At all other times this command acts the same as lt BACK S gt lt CTRL gt lt SHIFT gt lt RETURN gt Insert a lt RETURN gt Into the text The line containing the cursor is broken at the cursor The portion of the line to the left of the cursor remains on the current line The remainder of the line is inserted in a new left justified line immediately below the left hand portion or the old line The window is redrawn as needed Chapter 4 Technical Considerations 4 1 Files from Other Text Editors The editor can t handle files which don t contain lt RETURN gt characters EOL s or have Lines longer than 240 characters Line lengths should be less than or equal to the line
181. ting one record partially on top of another idinfo POINTER newrecord Here we are defining a pointer to the type idinfo We can fill fields of a virtual record in the array simply by pointing the pointer to the first field in one of the virtual records and then using the pointer in a record reference to access a single field newrecord idarray recount recordsize This assignment makes the pointer point to the end of the array It does this by adding the space occupied by all the other records to the starting address of the array The space occupied by all the other records is simply the number of records reccount times the size of each record recordsize newrecord XXX xxx XXX is one of the field names of the record type and xxx is the corresponding input function used to fill the array Since we made newrecord point to the end of the array we can start filling in the new record Wecan use the pointer in the record reference because we declared it as a pointer to that record type recount 1 Here we are simply incrementing the variable that keeps track of the number of records currently in the array We do this because we just put another one in In example 4 we will use this array we ve filled to verify the information typed in by someone trying to gain entrance into a restricted area by making sure they key in the proper secret code but we ll have to remember to access the array as an arr
182. to communicate with the ATARI machine and tell it to do things You write a program in the ACTION Language and then tell the ACTION Compiler to translate it into a form the computer can understand machine language and then you run the program Why is this such an involved process BASIC isn t like that First of all the process isn t that involved once you understand what s going on and why Secondly BASIC isn t like that because it is an Interpreter not a Compiler BASIC translates each line as the program is running and it takes some time to do that thereby slowing down the speed of your program ACTION on the other hand breaks the running and syntax checking of your program into two parts The Compiler checks your program for proper syntax and does the translating When it is through your program can be run directly i e without any syntax checking This makes your program run with incredible speed As mentioned in the previous paragraphs the ACTION Compiler translates an ACTION program into machine code The only thing it requires is that the program be in proper ACTION form The compiler will give you an error if you use syntax which is illegal in the ACTION Language just like an English teacher would give you an error Or red mark if you used improper English in class The ACTION system also contains a group of prewritten routines which you can use in your programs This group of routines is called the ACTION
183. tring gt is the main string lt substr gt is the substring we want to find in the main string lt errptr gt is a pointer to a byte error flag lt nofindptr gt is a pointer to a byte substring not found flag This kind of parameter manipulation takes some practice if you re not used to the concept of pointers but is a quick and easy way get more information passed out of a routine without having to resort to using global variables This means that the routine remains multipurpose as discussed in section 6 4 Part V The ACTION Compiler Chapter 1 Introduction 1 1 Vocabulary 1 2 Compiler Directives Chapter 2 Compiler Operation 2 1 Comments SET DEFINE 2 2 Variable Allocation 2 3 Routines 2 4 INCLUDEd Programs 2 5 MODULE 2 6 Symbol Tables Chapter 3 Using the options Menu Chapter 4 Technical Information 4 1 Overflow and Underflow 4 2 Type and Boundary Checking 4 3 Channel 7 Restriction 4 4 Available Space Part V The ACTION Compiler Chapter 1 Introduction Atari BASIC offers you great convenience in that you can write a program in a somewhat English like language then immediately test that program without going through any other steps This twofold advantage is gained at the expense of requiring that each command on each line be figured out by a special program called the BASIC interpreter at the time of execution ACTION is somewhat more sophisticated It requires that your program be figured
184. ue n RETURN CARD FUNC findmatch CARD testidnum idinfo POINTER seeker points to each record In turn to do test BYTE ctr used as a counter in the FOR loop FOR ctr 0 TO reccount 1 minus one because we DO start at 0 not 1 seeker idarray ctr recordsize index record IF seeker idnum testidnun THEN test for an RETURN seeker 1 D match and return FI if found OD RETURN 0 no match found End of FUNC findmatch PROC main This procedure controls the whole shebang Idinfo POINTER recptr pointer to a record BYTE POINTER namepir _ pointer to name field CARD id_num D nximber input by user code num code number input by user keyid 65535 1 D number allowing loop exit BYTE mode controls the operation mode PrintE Startup PrintE What operation mode PrintE X expand list of employees PrintE A alert test input mode Print gt gt mode InputB read mode IF mode A OR mode a THEN anything but A or a fillinfo will go to X mode ELSE sinterrogation routine DO loop start Print Employee I D number gt gt id_num InputC get I D number IF id_nuni keyid THEN enables exit from EXIT the infinite loop ELSE a normal I D number i e not keyed recptr findmatoh id_nuin look for D match IF recptr 0 THEN no match PrintE DO NOT PASS ELSE an I D match Print Code Number gt gt code_num lInputC get access code IF recptr codenum
185. using an UNTIL loop Notice that guess is not initialized in the variable declaration as it was in the WHILE equivalent We can do this because the conditional expression guess num is not evaluated until we have gotten a guess from the user This is one of the advantages of the UNTIL loop and stems from the fact that the controlling conditional expression is at the end of the loop WHILE requires evaluation of the conditional expression at the beginning of the loop and so requires that guess have a value 5 2 5 Nesting Structured Statements As mentioned in the overview of statements structured statements are made up of other statements together with some execution controlling information particular to a given structured statement The statements within the structured statement may be either simple statements or other structured statements Putting one structured statement inside of another is called nesting because one of them is nested inside the other In sections 5 2 4 2 WHILE and UNTIL you can see examples of nesting an IF statement into WHILE and UNTIL loops This type of nesting is very straightforward and needn t be discussed further This section will deal with multiple nesting of the same type of structured statement IFs inside IFs FORs inside FORs etc When the IF statement is nested inside itself confusion might seem to arise when trying to figure out what ELSE goes with which IF as you go deeper int
186. width of your printer for the sake of convenience 4 2 Key Recognition During command line entry in the message area only the lt ESC gt lt BACK S gt and lt CLEAR gt command keys are recognized All text characters are allowed During regular text entry all text characters and commands are allowed 4 3 Out of Memory Error This condition can result from an editing session in which you made quite a few insertions and or substitutions or from typing in a file which is too big this will occur very rarely When you get this error immediately write the text file out to a storage device and then restart ACTION using the BOOT command in the Monitor You can then go back to the Editor and read your text file back in and continue working on it Part Ill The ACTION Monitor Chapter 1 Introduction Chapter Chapter 3 Vocabulary Concepts and Features ACTION Monitor Commands BOOT Restarting ACTION COMPILE Compiling Programs DOS Transfer to DOS EDIT Transfer to the Editor OPTIONS The Options Menu PROCEED Restarting Programs RUN Program Execution SET Setting a Memory Value WRITE Saving Compiled Programs XECUTE Immediate Commands Display a Memory Location Memory Dump Program Debugging Facilities Part Ill The ACTION Monitor Chapter 1 Introduction Part Ill describes the ACTION monitor control center of the ACTION system It connects to all of the funct
187. will be lost Compiled programs and their program variables will also be lost 2 2 COMPILE Compiling Programs In ACTION a program must be processed by the ACTION compiler before it can be run from the monitor You can call the ACTION compiler from the monitor using FORMAT COMPILE lt filespec gt The lt filespec gt is an option which allows you to compile programs which are stored on a peripheral device disk cassette etc If no lt filespec gt is specified then the contents of the Editor buffer is compiled If you are using two windows the file in the window which contained the cursor when you left the Editor is compiled If the Compiler finds a syntax error while compiling the program the error number and the line on which the error occurred are display in the Monitor s message area The Compiler then returns control back to the Monitor Examples r COMPILE lt RETURN gt compile the program in the current Editor window C lt RETURN gt C C lt RETURN gt compile from cassette C D1 PRIME ACT lt RETURN gt compile PRIME ACT COMPILE PRIME ACT lt RETURN gt from disk drive 1 Notice that the file name specified in the last example does not have a device given If no device is given the device D1 is assumed 2 3 DOS Transfer to DOS You can transfer to OS A DOS XL or Atari DOS by entering DOS then pressing lt RETURNS gt Examples DOS lt RETURN gt D lt RETURN gt NOTE S
188. worry about lt parameter list gt and RETURN in the format because they ll be discussed later The rest should look somewhat familiar so we ll give an example PROC gueesuntil This procedure plays a guessing game with the user using an UNTIL loop BYTE num the number to guees guess the user s guess PrintE Welcome to the guessing game I m PrintE thinking of a number from 0 to 100 num Rand 101 get the number to guess DO start of UNTIL loop Print What is your guess Guess inputB get the user s guess IF guess lt num THEN guess too low PrintE Too low try again ELSEIF guess gt num THEN guess too high PrirtEt Too high try again ELSE guess just right PrintE Congratulations PrintE You got it Fl end of guess testing UNTIL guess num floop control OD end of UNTIL loop RETURN end of PROC guessuntil This is just the program example from section 5 2 4 3 but now you understand why the PROC statement and the variable declaration section are there As mentioned in the introduction an ACTION program requires a procedure declaration or a function declaration to be compilable The above example has a procedure declaration so it is a valid ACTION program and as such may be compiled and run It s output is the same as that given in the UNTIL section namely Welcome to the guessing game I m thinking of a number from 0 to 100 What s your guees 50 Too low try again What
189. y a Memory Location You can display the value either of a variable or of a specified memory location Enter Then enter a compiler constant Press lt RETURNS gt The format is lt compiler constant gt lt RETURN gt The ACTION monitor shows you the actual memory location expressed in both decimal and hexadecimal formats followed by the printable ATASCII value of that location its four digit hexadecimal value the decimal value of the BYTE and the decimal value of the CARD starting at the specified location If the identifier is not in the ACTION compiler s symbol table then a variable not declared error occurs Example gt FFFE 65535 fffe s e6f3 243 59123 NOTE the results might not be what you expect if memory has been altered since the compile see SYMBOL TABLE in Part V 2 12 Memory Dump Starting from a specified memory address you can display the memory contents of sequential locations in a format identical to that described just above Simply enter and the lt address gt The format is lt address gt lt RETURN gt The monitor returns a list of the memory contents in the variety of formats mentioned above at the rate of one line per memory location You can stop the listing by pressing lt space bar gt You can temporarily halt the listing by entering lt CTRL gt 1 Press lt CTRL gt 1 a second time to continue the listing Example 1536 0600 0000 0 0 1537
190. y can be turned off for greater speed during disk I O and during ACTION Compiler processing You can turn the screen display off enter N or you can leave it on enter Y Bell Y M C E The bell rings whenever errors are encountered in the ACTION Monitor Compiler or Editor It also rings whenever the ACTION monitor is called You can turn that bell off enter N or you can leave the bell on enter Y Case sensitive N C When this option is Y distinction is made in variable names between upper and lower case letters i e count differs from Count and COUNT and the language statements e g FOR WHILE DO etc must be in upper case However for the ease of beginning ACTION programmers case sensitivity is turned off when you enter the ACTION system Trace N C With this option you can control the compiler s ability to trace program compilation When this option is enabled Y the compiler will note in the Monitor s message area every routine call together with the parameters passed to that routine See chapter 4 for more information on the usage of this option List N C The ACTION compiler can be commanded to display the current line being compiled in the message area of the screen Enter Y to enable this listing or enter N to disable this listing Window 1 size 18 E The size of the ACTION Editor s window 1 is set explicitly Window 2 size is set implicitly by the relationsh
191. y of ACTION Monitor Commands B restart ACTION system compile an ACTION program C lt flleftpec gt D call DOS E go to the ACTION Editor O go to the ACTION Options Menu P proceed from program halt R lt fllespec gt run an ACTION program SET lt address gt sets a value in a specified memory location lt value gt W lt flleflpecs save a compiled program to disk X lt statement gt lt statement gt execute ACTION language statement s lt address gt display value of an address or compiler constant lt address gt display values of all addresses starting at an address or compiler constant Appendix G Options Menu Summary prompt default range Comment Display on Y Yor Controls the screen during compile amp N device I O Bell off N Yor Controls bell response N Case insensitive N Yor Controls the compiler check for upper N case key words in the language and the case distinction in variable names Trace on N Yor Controls compiler setup of programs so N that the program during execution notes entry into any PROCedure or FUNCtion List on N Yor Controls compiler listing of program N lines to screen during compile process Window size 18 5to Controls window 1 size Window 1 and 18 window 2 combined use 2 3 lines Line size 120 1to Controls l
192. y one is the same as multiplying by two and a RSH by one is like division by two for positive numbers In fact this method of multiplication and division is faster than using 2 and 2 because it is closer to what the computer understands so the computer doesn t need to translate the expression into its own binary operation format The operator gives the address of the variable to its right It cannot be used with numerical constants ctr will return the address in memory of the variable ctr The operator is very useful when dealing with pointers 4 1 3 Relational Operators Relational operators are allowed only in relational expressions and relational expressions are allowed only in IF WHILE and UNTIL statements Relational operators may not appear anywhere except in these statements As outlined in the overview of this section relational operators test conditions of equality A table of the ACTION relational operators follows Table 6 Relational Operators z Test for equality Example 4 7 this is obviously false Test for inequality Example 4 7 True lt gt Same as gt Test for greater than Example 9 gt 2 True gt Test for greater than or equal to Example 5 gt 5 True lt Test for less than Example 2 lt 9 True lt Test for less than or equal to Example 5 lt 5 True AND Logical AND See section 4 4 OR Logical OR See section
193. you compile the program every time the compiler sees FROG it will think to Itself Oh he really means CARD so I ll just put that in instead Here are some more examples to let you become thoroughly familiar with the form DEFINE listen SET 49A 1 DEFINE begin DO end OD DEFINE one 1 NOTE Don t forget that the string constant must have double quotes around it see section 3 2 To better show you what DEFINE does and doesn t do here s a table showing the effects of a DEFINE on different program parts statement comments DEFINE four 4 the directive PrintBE four prints 4 with EOL four score and converts four to 4 four score and does not alter four score PrintE four score does not replace inside quotes 7 2 INCLUDE The INCLUDE directive allows you to include other programs into the program being compiled Suppose you have a program named IOSTUFF ACT that does input output functions and you want to use the I O routines it offers in some other program you re writing now All you need to do is put the following command in the program you re writing INCLUDE D1 IOSTUFF ACT NOTE The file specifier must have double quotes around it The above statement must come before you use any of the I O routines in the file IOSTUPF ACT Note that this example assumes that the diskette with OSTUFF ACT on it is in disk drive D1 If you don t specify

Action manual - Noni Kimbel and Jim Patchell

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