Programmers' Reference Guide for the Atari 400-800 ... - Atarimania

Copyright

© 1984

by David Heiserman

FIRST EDITION FIRST PRINTING

All rights

reserved. No part of this book shall be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from the publisher. No patent liability is assumed with respect to the use of the information contained herein. While every precaution has been taken in the preparation of this book, the publisher assumes no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use of the information contained herein.

International Standard Book Number: 0-672-22277-9 Library of Congress Catalog Card Number: 83-51616 Edited by Welborn Associates Illustrated by D.B. Clemons

and 8001" are trademarks of and used by permission of Atari, Inc. ATARl®, 4001"

book is published by Howard W Sams & Co., Inc. which is not affiliated with Atari, Inc. and Atari is not responsible for any inaccuracies. This

Printed in the United States of America.

David L. Heiserman has been a freelance writer since 1968. He is the author of more than 100 magazine articles and 20 technical and scientific books. He studied applied mathematics at Ohio State University and is especially interested in the history and philosophy of science. He is the author of the Sams books Intermediate Programming for the TRS-80 and Intermediate-Level Apple ll Handbook.

That is not to say that a beginner cannot learn anything from this book-quite the contrary. The organization of material in this book is most satisfactory for a beginner who has a desire to experiment with new ideas and techniques on a first-hand basis. Although such an individual might not fully understand the finer points of some topics, the mere effort guarantees a level of success that is often difficult to achieve from simpler, step-by-step presentations. would like to acknowledge the invaluable assistance offered by my personal secretary, Robin M. Yates. She prepared many of the tables and drawings, proofread the drafts, and assembled the final manuscript for us. I

DAVID HHSERMAN

CHAPTER 2 ATARI BASIC Notation, Rules, and Limitations NUMERIC AND STRING CONSTANTS

.................

Numeric Constants .................... String Constants .........................

BASIC VARIABLES AND VARIABLE NAMES

....

Numeric Variables ................................. String Variables ......................................

DIMENSIONING STRING VARIABLES AND NUMERIC ARRAYS

..................................................

D|Mensioning String Variables .................... Subscripted Numeric Variables and Arrays ....

OPERATIONS AND OPERATORS

................

Arithmetic Operators ...................... Relational Operators ............... Logical Operators ...................... Order of Precedence for Operators .....

CHAPTER 3

The BASIC Programming Language A SUMMARY

or

FUNCTIONS A SUMMARY

.,............_

STATEMENTS, COMMANDS, AND

................................................

or ATARI

BASIC SYNTAX AND APPLICATIONS

CHAPTER 4

The Text and Graphics Screens FEATURES

COMMON TO

...............

ALL SCREEN

MODES __ MODE-0 GRAPHICS ._....__._..........._......._._. Organization of the Mode-0 Color Registers ....... Working With the Mode-0 Column/Row Format .... Working With the Mode-0 Margins ................ Using the POSITION Statement ................. Alternative Column/Row Techniques ....... .__ Using LOCATE, GET, and PUT in Mode 0 .... ._ The Mode-0 Screen RAM Format ........... ._ MODE-1 AND MODE-2 GRAPHICS ..____.__.____....... . Organization of the Mode-1 and Mode-2 Color Reglsters .__._..._..._......._......_..._....___._. Accessing the Character Set From Modes 1 and 2 ....___.. Working With the Mode-1 and -2 Column/Row Format __ Using the POSITION Statement _......__...._..._..._.._._ Alternate Column/Row Techniques ._..._..____..._._ _._ Using LOCATE, GET, and PUT in Modes 1 and 2 ._.__. The Mode-1 and Mode-2 Screen RAM Formats __.. Full-Screen Formats __.._.._..._....__.......___.._.._.._.._ CUSTOM CHARACTERS SETS FOR MODES 0, 1, AND 2 _.__._. _

_

_

_

_ _

_

_

_ _

_

.......................... ............... ........................................

USING THE XIO COMMAND Controlling Outgoing Lines With XIO 34 Configuring Baud Rate, Word Size, and Stop Bits with XIO 36 Setting Translation Modes and Parity with XIO 38

_

......

CHAPTER 7 A

Miscellany of Principles and Procedures ....

.

.......... The SOUND Statement .............., Reproducing Musical Scores .......

MORE ABOUT THE SOUND FEATURES

Experimenting With Sound Effects

._

_

....

.................. ................

MORE ABOUT THE USR FUNCTION Passing Values to a Machine Routine Passing Values From a Machine Language Routine SCREEN DISPLAY LISTS

A LOOK AT TOKENIZED BASIC

. .

.

CHAPTER 8 The ATARI Memory Map .............

_

.............

.............

_

_

.......

ZERO-PAGE AND STACK RAM OPERATING SYSTEM AND BASIC RAM ._._ Operating System RAM: 512-1151 .... BASIC System RAM: 1152-1535 .._.. DOS RAM USAGE: 1792-10879 .........__. BASIC ROM AREA: 40960-49151 .._.._._____ HARDWARE I/O ROM AREA: 53248-55295 .. The CTIA (or GTIA) Device

_

.....

................................... .........................

The ANTIC Instruction Set Structure of a Display List ..... Locating the Display List ......

_

_

_

_

. _

_

_

The POKEY Device ............._.._.. The PIA Device ....._.._.__..._.._.__....._ THe ANTIC Device __._............._.....__. OPERATING SYSTEM ROM AREA: 55296-65535

_

_

_

_ _

_

CHAPTER 9

The 6502 Instruction Set

...............

.

APPENDIX A

Number-System Base Conversions ..........

............. .............

HEXADECIMAL-TO-DECIMAL CONVERSIONS DECIMAL-To-HEXADECIMAL CONVERSIONS CONVENTION/\L DECIMAL TO 2-BYTE DECIMAL FORMAT

Fig. 1-2. The ATARI

800 Home Computer console. (Courtesy Atari,

Inc.)

There are a couple of less-obvious differences. For one, the ATARI 800 Home Computer can accept two different program cartridges, while the 400 can accept only one. Fig. 1-3 shows the arrangement of jacks and switches along the right-hand side of the ATARI 800 console unit. The arrangement for the model 400 is similar, but does not include the MONITOR jack. That simply means that the 400 must use an ordinary tv receiver as its display screen, while the 800 offers the option of using a tv receiver or a monitor.

PER|PHERAL

MONITOR

Fig. 1-3. Connection panel for

I 2-CHAN-3

Pom”

_ ' ggvgfgl

l

the Model 800. The Model 400

identical except for the lack of

a

is

MONITOR jack.

For the most practical purposes, however, the 400 and treated as such throughout this book. Also, it will be assumed through this book that the ATARI BASIC cartridge is installed. As far as the 400 model is concerned, that means plugging it into the only slot that 800 models are identical, and they are

14

The power-transformer assembly is plugged into an ordinary 120 V ac outlet, and the smaller plug goes into the POWER IN jack on the side of the console unit. A cable and plug attached to the rear of the console goes to the antenna terminals on a standard tv receiver. lf you plan to use the tv for viewing ordinary programming, that antenna connection should be made through an antenna switch that is provided with the basic unit. To get this configuration into operation: 1. Turn on the tv set. 2. If you are using the

antenna switch, set the switch to

its COMPUTER position.

Turn on the computer console, using the POWER switch located on the left-hand side of the unit. 4. Set the CHAN switch on the side of the console for either Channel 2 or 3, and match the tv channel selector accordingly. Use the channel that can be tuned for the lesser amount of outside interference. 3.

When all is going well, the tv will show a blue background color, a lighter blue READY message, and a lightblue square just below the message. At that time, the system is ready to operate in ATARI BASIC.

lf you have an ATARI 800 system and wish to work with a monitor unit instead of a tv receiver, the hardware arrangement is somewhat simpler. You have no need for the antenna switch nor the tv cable coming from the back of the console. Simply run the monitor cable from the 5-slot MONITOR jack on the side of the console to the video and audio input terminals on the monitor. The CHAN selector switch setting is not relevant at all.

Minimum System Plus Program Recorder Fig. 1-5 shows the minimum system configuration as extended to include the ATARI 410 program recorder. Using the program recorder enables you to save programs on the magnetic tape in a standard tape cassette, and then reload those programs at some later time. 16

Turn on the tv receiver or monitor, and then insert a diskette into the disk-drive unit. That diskette must be properly formatted and include the DOS system programming (the DOS system disk supplied with the disk assembly will include that programming). Next, turn on the disk-drive unit. Do not have the console unit turned on at this time. Only when the disk drive stops running (the red light will go out) should you turn on the console.

Common Multiple-Peripheral System Fig. 1-6 illustrates one of the most common ATARI configurations: the basic console unit, a tv receiver or monitor, a single disk-drive unit, a model 850 serial interface module, and a printer. The start-up sequence for such arrangements is quite A

critical.

In

this particular case:

Turn on the tv set or monitor. Insert a diskette containing the DOS system programming into the disk-drive unit. 3. Turn on the disk-drive unit and wait for the drive to stop running. 4. Turn on the 850 serial interface module. 5. Turn on the printer. 1. 2.

There are many other possible configurations that can be far more complex that these-using multiple disk drives, for instance. Consult the manuals that are supplied with the peripherals for exact details. Generally speaking, however, the turn-on procedure follows the same general plan: turn on the tv or monitor, boot DOS by turning on disk-drive 1, turn on the console, turn on the interface module, and turn on peripherals that are connected through the interface module.

18

Much of the material remaining in this book deals with the nature of those BASIC commands. During the Course of working with those commands, however, it is often necessary or desirable to execute some special keyboard functions.

Some Control Keys Most of the ATARI computer keyboard

is identical to that of a conventional typewriter. There are some special keys and key functions that are generally irrelevant for ordinary typing operations, but quite important for operating a

computer.

The key is perhaps the most-used control key. You must strike the control key whenever you want the computer to execute a command that you’ve given it in a typewritten form. When you are ready to execute _a BASIC program, for example, you should type RUN on the keyboard, and then strike the key to get the computer to read andexecute the command. The special controlkey operations described in this section do not have to be followed by a keystroke, however. The two keys serve much the same function as the shift keys on an ordinary typewriter. There are some differences, though. For instance, when you turn on the ATARI system, you find that all letters of the alphabet are printed to the screen in an upper-case format. Depressing a key while typing letters of the alphabet will cause the system to print lower-case letters. That is just the

reverse of ordinary typewriters. It is possible to change the format by striking the key. Having done that, all letters of the alphabet are normally printed in their lower-case form; and you must hold down one of the keys in order to print upper-case letters. To return to normal upper-case printing, hold down one of the keys and strike the key again.

20

The four arrow keys located near the right side of the keyboard allow you to move the cursor to any desired point on the screen. In order to use them, however, you must be holding down the key at the same time. The key serves the purpose of the tab functions on an ordinary typewriter. Strike that key alone, and the cursor will jump to its next horizontal tab location on the screen. You can set new tab positions by first setting the cursor to the desired tab position, and then striking the key while holding down one of the keys. Finally, you can clear a current tab setting by holding down both the key and one of the keys while striking the key. The key is used for stopping the execution of a program. The key, like the key, changes the normal functions of other keys. Whereas you must hold down the key while striking another key, you use the key in sequence: first strike the key, release it, and then strike another key. The special and operations are described in later discussions in this book.

SOME SCREEN EDITING FEATURES When working in BASIC, it is often necessary to change some of the material printed in the program. The ATARI system offers some program-editing features that make the task much simpler. The most important point to bear in mind is that the ATARI screen is “live.” That is to say, what you see on the screen is what is actually in program memory. So change something on the screen, and you also change the programming as well.

22

If you wish, you can listen to the audio tones during a data recording or playback session. If you are using an ordinary tv set as a screen monitor for the system, simply turn up the volume control; or if you are using a monitor, make sure that the audio plug is inserted into the monitor’s audio input jack, and turn up the volume control on that unit.

Connecting the Program Recorder to the System Fig. 1-5 shows the arrangement of the system if you are using no peripheral devices other than a tv or monitor and the program recorder. The program recorder plugs directly into the peripheral connector on the side of the ATARI console unit. If the program recorder is used in conjunction with several other peripheral devices, it must be connected to the system through a serial interface module, and it must be the last peripheral in line. Saving and Loading Programs With the Program Recorder The most commonly used command for saving BASIC programs on cassette is CSAVE; and getting a BASIC program from tape and into the ATARI computer is by means of the CLOAD command. To save a BASIC program on the program recorder, first use the FAST FORWARD and REVERSE keys on the program recorder to find the end of any programming that currently exists on the tape. Note the reading on the recorder’s tape counter for future reference. Set the recorder to its record mode by depressing both the RECORD and PLAY levers; and immediately follow that by entering the following command at the ATARI console: CSAVE

24

ROUTINE DISK OPERATIONS Fig. 1-6 shows a disk-drive unit connected to the ATARI system. When using more than one disk drive, determine the proper installation procedures from the user’s manual. Assuming that DOS is properly booted as described earlier in this chapter, typing DOS and striking the key brings up the DOS menu-it is a convenient guide to running variety disk utility operations. See the two common versions of the DOS menu in Chart 1-1.

Chart 1-1. Two Common Versions of the DOS Menu DOS Version 1.0 DISK DIRECTORY RUN CARTRIDGE COPY FILE DELETE FILE(S)

FORMAT DISK DUPLICATE DISK BINARY SAVE BINARY LOAD RUN AT ADDRESS DEFINE DEVICE DUPLICATE FILE

RENAME FILE LOCK FILE UNLOCK FILE WRITE DOS FILE

DOS Version 2.0S

E.

F.

G. H.

DISK DIRECTORY RUN CARTRIDGE COPY FILE DELETE FILE(S) RENAME FILE LOCK FILE UNLOCK FILE WRITE DOS FILE

M. N.

O.

FORMAT DISK DUPLICATE DISK BINARY SAVE BINARY LOAD RUN AT ADDRESS CREATE MEM.SAVE DUPLICATE FILE

Displaying the Current Disk Directory Execute the DOS command from the keyboard, and then select menu option A. The system will respond by printing this prompting message: DIRECTORY-SEARCH SPEC, LIST FILE?

26

In a manner of speaking, the asterisk tells the system to work with any combination of letters and numerals in that part of the file name. By way of another example, suppose that you want to see the directory of all file names that begin with the letters ALT. This sort of response will do that for you:

D:ALT*.*

Returning to BASIC The all-around safest way to return to BASIC from the DOS menu is to strike the key. Alternatively, you can elect menu item B, but there is a chance that you will lose some BASIC programming that is resident in the system. Actually the purpose of DOS menu item B is to return program control to the resident cartridge. If that happens to be the BASIC cartridge, the system begins running in BASIC. Or if it is a special language or game cartridge, selecting menu item B begins execution of that program. Copying Files to the Same Disk DOS menu item C provides a means for copying files and programs onto their own disk. This feature is most often used for generating backup copies on the same diskette. Perhaps you are planning to revise a program that already exists on the disk. You want to save the original version, but create a copy that you can modify. That is the primary application of DOS menu selection C. Upon entering that selection, you will see this prompting message:

COPY FILE-FROIVLTO?

28

You can also use global (or “wild-card”) file names under the file-copying option. Suppose that you want to transfer all of the SYS, or system, routines from drive 2 to drive 1. The appropriate response to the prompting mes-

sage

is:

D2:*.SYS,D1:*.SYS Or if you want to copy all files beginning with FUS to the same disk, but add a BAK extension, the appropriate entry is:

FUS*.*,FUS*.BAK Finally, there is the option of merging disk files-adding the content of a source file to the end of an existing destination file. The only catch is that both files must have been saved in an ATASCII format (see Chapter 6). The general syntax of such an operation is:

source,dest/A where source is the file name for the source file, and dest is the file name of the destination file. The suffix /A is what prevents the source file from completely writing over the destination file.

Deleting Files There is little point in cluttering valuable disk space with files and programs that are no longer of any use. DOS menu option D allows you to delete, or erase, any unwanted programs or files. Upon selecting menu option D, the system displays this

prompting message:

DELETE FILE SPEC

You should respond by

entering the name of the file to be deleted. And if you enter a file name that exists on the disk, the system will ask you whether or not you really want to delete it: TYPE "Y" TO DELETE.

30

,

Locking Files DOS menu option F allows you to lock a file so that it cannot be changed or renamed as long as the file remains locked. Responding with that menu selection brings up this prompting message: WHAT FILE TO LOCK?

Simply respond by entering the name of the file-one that already exists in the directory. You can use the global option to lock all files having a

specified name or extension in common. It is a good idea, for example, to lock all SYS files so that they cannot be inadvertently changed, erased, or renamed. Do that by responding with: *.SYS

Unlocking Files There are instances where it is necessary to unlock a previously locked file; perhaps to modify it or erase it altogether. DOS menu option G offers this feature. Selecting that option brings up this sort of prompting message: WHAT FILE TO UNLOCK?

Simply respond with the name of the file to be unlocked, and the computer will take care of the task for you.

Copying DOS files finished disk of BASIC programs ought to contain the system files that boot DOS for you. That circumvents the troublesome need to boot DOS with a special systems disk and then replacing it with your working BASIC disk. Electing DOS menu item H does that for you. The mechanical procedures are different for DOS 1.0 and 2.05. If you are using version 1.0, the system prints this A

prompting message:

TYPE "Y" TO WRITE NEW DOS FILE

32

The general idea is to respond with the disk-drive number of the disk to be copied (the source disk), a comma and the disk-drive number of the new copy (the destination disk). The appropriate response and operations from that point are slightly different, depending on whether you have one or two disk drives available. If you have just one disk drive available, you must respond to the prompting message by entering 1,1. That, in effect, says that the source and destination disks will both be in drive 1. Obviously you cannot fit two disks into the same drive unit, so the system will respond with this message: lNSERT SOURCE DlSK, TYPE RETURN

Insert the disk to be copied and strike the key. The system will load up the ATARI RAM with disk data; and when it is full, you will see this message: INSERT DESTINATION DISK, TYPE RETURN

Respond by replacing the source disk with a clean and formatted disk, and striking the key. The system will then load the most recent blocks of data to that disk. When using a single disk drive in this fashion, it is often necessary to alternate the source and destination disks several times. This swapping operation will come to an end only after the entire contents of the source disk is copied to the destination disk. Things are a lot simpler for the operator when two disk drives are available. Electing the disk copy operation, as before, brings up this prompting message: DUP DISK-SOURCE,DEST DRIVES?

Respond by entering two different disk-drive numbers: the source followed by the destination. Suppose that you want to copy the content of the disk in drive 1 to a fresh disk in drive 2. That being the case, the appropriate response to that prompting message is: 1,2

34

Upon selecting DOS menu item O, the system prints this prompting message: NAME OF FILE TO l\/IOVE?

Respond with the file name of the file to be copied. Having done that, the system will prompt you to insert the source disk and strike the key. After that, it prompts you to replace the source disk with the destination disk-and strike the If the file is a fairly long one, you will have to switch the source and destination disks several times.

key.

The Machine-Language Options DOS menu items K, L, and M deal with machine-language

program operations. Chapter 6 describes these operations in detail.

Saving and Loading Programs With the Disk Drives Starting with a properly formatted diskette, simply insert the diskette into a drive unit and enter a command of this general form: SAVE "D[n]":fi/ename[.ext]

That command includes a couple of optional expressions that are included in brackets. Expression n is necessary only when (1) using more than one disk drive and (2) you want to save the program on a drive other than drive No. 1. The filename is not optional, and it must follow these general rules:

must be composed of nothing but numerals and capital letters. It must be no more than eight characters long. It must begin with a letter of the alphabet.

1. It 2. 3.

36

Numeric Constants A numeric constant is some fixed numerical value. Here are a few numeric constants that are expressed in rather familiar forms: 23

- 212

1.6888

9.9999

1432000

Numeric constants can be very small or very large numbers, they can be positive or negative, and they can be whole numbers or numbers having decimal parts. just ordinary number values-that is all numeric constants are. There are a few special rules, limitations and forms of notation that apply to numeric constants in BASIC. For one, large numbers must not use commas in the conventional fashion; in fact they must not use commas at all. So if you wish to express a value of one million in BASIC, you must enter it as 1000000, and not as 1,000,000. In keeping with the usual arithmetic convention, negative-valued numeric constants are preceded by a minus sign, while positive values can be expressed with a plus sign or no sign at all. If you enter a PRINT -128 command, for example, ATARI BASIC will respond by printing - 128 on the screen. But if you enter a PRINT +128 command, BASIC will exercise the no-sign option and print 128. ATARI BASIC uses a number format called floatingpoint notation. Among other things, that means it expresses very large and very small values in terms of powers-of-10, or scientific notation. Very large numbers, in this context, are positive or negative numbers having more than nine digits to the left of the decimal point; and very small numbers are those between -0.01 and 0.01. To see how ATARI BASIC handles very large values, enter this command: PRINT 12345678901 and you will see this response:

1.2345678901

40

E+1 O

The same principle applies to fractional numbers. A constant such as 0.00123456789123456789 has 20 significant digits to the right of the decimal point. Eighteen of them are nonzero digits, so ATARI BASIC will treat the number as 0.00123456789 and display it as 1.23456789E-03. Summarizing the limitations and conventions required for numeric constants in ATARI BASIC: 0 Large numeric values must not include commas. O A negative sign ( - ) must precede a negative-valued constant, but a plus sign +) is optional for positivevalued constants (ATARI BASIC will always print positive values without the plus sign). 0 ATARI BASIC uses scientific notation for expressing very large and very small numeric constants. O ATARI BASIC will deal with only nine nonzero significant digits; any beyond that number will be set to (

zero.

String Constants Whereas numeric constants must be composed of meaningful numeric values, string constants can be constructed of any combination of letters, punctuation marks, special symbols and numerals. What’s more, string constants usually must be enclosed in quotation marks. The following BASIC statement prints a string constant, HELLO:

PRINT "HELLO"

The string constant in that instance is composed entirely of upper-case letters of the alphabet and, as is usually the case, the constant is enclosed in quotation marks. When you execute that PRINT command, however, you will see ATARI BASIC printing HELLO without the quotes. As implied earlier, a string constant can be built from all sorts of letters and punctuation. For example: PRINT "Hello,

42

there, you silly goose!"

NOTE: There is

a special string constant that contains no characters whatsoever. It is defined by a pair of successive quotation marks, '”’, and is called the null string.

Summarizing the rules and limitations for expressing string constants:

0

most instances, string constants must be enclosed quotation marks. (The special exceptions will be described in later discussions.) 0 String constants may be composed of any characters except a quotation mark. 0 Numerals appearing within a string constant are treated as literal characters rather than numeric values. I The recommended maximum length of a string constant is 130 characters. In

in

BASIC VARIABLES AND VARIABLE NAMES Most arithmetic and control operations in BASIC make reference to variables and, particularly, variable names. A variable is an expression that can take on a wide variety of different values-values that are assigned to variables through the normal execution of a program. A variable name is a set of one or more alphanumeric characters that you, the programmer, devise yourself according to a few simple rules. NOTE: ATARI BASIC allows up to 128 different variables to be used through the execution of a program.

BASIC uses two kinds of variables: numeric variables and string variables. The following discussions point out their differences.

44

3.

Numeric variable names should not include the words shown in the Reserved Word List, Chart 2-1. (Although ATARI BASIC will usually accept variable names from the Reserved Word List, there are many instances where such names will cause an Errorinterrupt during the execution of a program.)

Chart 2-1. ATARI BASIC Reserved Words List ABS ADR AND

RESTORE

IF

INPUT INT

ASC

RETURN RND RUN SAVE

CLOSE

LEN LET LIST LOAD LOCATE LOG LPRINT

CLR

NEW

SOR STATUS

COLOR COM CONT

NEXT

STEP

NOT NOTE ON OPEN

STICK STRIG

OR PADDLE PEEK PLOT POINT

END ENTER EXP FOR FRE GET

THEN TO TRAP USR VAL

POKE

XIO

GOSUB GOTO GRAPHICS

RAD READ REM

ATN BYE CLOAD CHRS CLOG

COS CSAVE DATA DEG DIM

DOS DRAWTO

SETCOLOR SGN SIN

SOUND

STOP STR$

POP POSITION PRINT PTRIG PUT

These words should not be used as variable names, nor should they appear within variable names. It is possible to break that rule in many instances, but a wise programmer will avoid the risks involved. NOTE:

Here are some examples of valid numeric variable names: TRY

46

AXIS

MODEL1

NAMESFROMTABLE100

There has to be at least one valid character and a dollar sign in a string variable name, but the maximum number of characters is limited only by the ability to fit the name into the lines of BASIC programming that use it. 4. String variable names should not include the words shown on the Reserved Word List, Chart 2-1. (Like some numeric variable names, ATARI BASIC will often accept variable names from the Reserved Word List, even when appended with a dollar-sign symbol; but the risk of causing an Error-interrupt during the execution of a program makes it unwise to use such names.) Here are some examples of valid string variable names: 3.

TRY$

AX|S$

MODEL1$

NAMESFROMT/\BLE`l0$

And here are some invalid string variable names: NYS

lTRY$ DARUNG-SETS MlX$lV|0NEY$ CHRS SALT

(uses lower-case letters) (begins with a numeral) (includes punctuation) (includes $ as punctuation) (uses a reserved word) (does not end with S)

NOTE: All string variables must be DIMensioned before they are used in a program. See DIMENSIONING String Variables and Numeric Arrays.

DIMENSIONING STRING VARIABLES AND NUMERIC ARRAYS

statement is always important for setting the DIMension of numeric and string variables. It is especially important in ATARI BASIC because it is required for establishing the maximum length of constants that are assigned to every string variable in the program. The DIM statement also sets up subscripted numeric variables and multidimensional numeric arrays. ln spite of appearances to BASIC’s DIM

48

Line 10 dimensions string variable NA$ for a maximum of 5 characters, but line 20 assigns a string constant that has

characters in it. When line 30 prints the current string constant that is thus assigned to NAS, it will show only the first 5 characters: SOMET. In actual practice, it is often inconvenient, and sometimes impossible, to determine the maximum number of characters that will ever be assigned to a given string variable. The temptation in such instances is to go overboard, and dimension the variable at some large figure; say, DIM X$(200). That should be avoided wherever possible, however, because the dimensioning operation reserves memory space for the string characters; and using needlessly large dimensioning values uses up memory that might be put to better use. Incidentally, a CLR statement within a program clears all previous dimensioning specifications. That can, in effect, make it possible to redimension a string variable during the course of a program. But CLR makes it necessary to redimension all string variables to be used and sets the DATA pointer to the first item in the lowest-numbered data list. In other words, the notion of using a CLR statement to redimension a variable during the execution of a program is of questionable value. Summarizing the procedures for dimensioning string 9

variables:

0 All string variables must be dimensioned with regard to the maximum number of characters they can

handle.

0 String variables must be dimensioned prior to using

them, generally gramming.

in

one of the first lines of pro-

0 String variables cannot be dimensioned more than one time during the execution of a program unless a CLR statement is first used to zero-dimension all pre-

viously dimensioned variables.

50

The idea is to indicate the sum of four different numeric variables that are closely related, but are able to take on different numeric-constant values. Because BASIC does not use subscripted characters, it is necessary to indicate

those characters within parentheses. Here form of the “textbook” equation just cited:

is

the BASIC

Y=X(1 )+X(2)+X(3)+X(4) A program cannot refer to such subscripted numeric variables in ATARI BASIC without first dimensioning them with regard to the largest-value subscript you intend to use. So before it is possible to execute that BASIC statement, the program must include a DIM X(4) statement. The general form of a subscript dimensioning statement ns:

DIMnumvar(d)

where numvar is any valid numeric variable name, and d is the largest subscript index to be used. Thus a typical line of programming for dimensioning several subscripted numeric variables might look like this: 10 DIM X(3), FE(20), YY(9)

That one will dimension subscripted variable

X for four variables-X(0) through X(3). By the same token, it dimensions FE for subscripted variables FE(0) through FE(20), and YY for YY(0) through YY(9). The following program prompts you to enter four different numbers. After that, it displays the four numbers, their sum, and their average. In this particular case, the numeric values are assigned to subscripted variables N(0) through N(3) by means of INPUT and assignment state-

ments within a FOR NEXT loop. It can be very helpful to realize that the execution of a RUN command automatically sets any subscripted numeric values to zero. That eliminates the need for zeroing them as one of the first steps in a program. .

52

_

.

The next program lets the user enter two different words, prints them in alphabetical order, and asks whether or not the user wants to do the whole operation again.

10 DIM K$(1),X$(10),Y$(10) 20 PRINT "ENTER A WORD "; 30 INPUT XS 40 PRINT "ENTER A SECOND WORD "i 50 INPUT YS 60 IF XS > =YS THEN PRINT YSZPRINT XSZGOTO 80 70 PRINT XSZPRINT YS 80 PR|NT:PRINT "DO AGAIN (Y/N)"; 90 INPUT KS 100 IF KS="N" THEN END 110 PRlNT:PRlNT:GOTO 20 Program lines 20 through 50 prompt the user to enter two words and, in the process, the statements assign those words to X$ and Y$. The conditional statement in line 60 compares the two words; and if XS occurs later alphabetically, or is identical to YS, the program prints YS followed by X$. But if the relational condition in line 60 is not satisfied, the program executes line 70 to print XS followed by Y$.

As mentioned earlier in this discussion, there is something more to using strings with relational operators than looking at alphabetical arrangements. BASIC actually looks at the strings in terms of the ATASCII code number for each character. (ATASCII is an acronym for ATari ASCII; and ASCII is an acronym for the standard charactercoding format, American Standard Code for Information Interchange.) Table 2-3 shows the ATASCII code numbers for the characters most relevant to this discussion; and a complete listing appears in Appendix B.

60

' '

Table 4-14. Starting and Ending Addresses for Each Row of the Mode-4 Screen RAM Row Row O Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Row 7 Row 8 Row 9 Row 10 Row 1 1 Row 12 Row 13 Row 14 Row 15 Row 16 Row 17 Row 18 Row 19 Row 20 Row 21 Row 22 Row 23

Addresses

Start 40320 40330 40340 40350 40360 40370 40380 40390 40400 40410 40420 40430 40440 40450 40460 40470 40480 40490 40500 40510 40520 40530 40540 40550

End

40329 40339 40349 40359 40369 40379 40389 40399 40409 40419 40429 40439 40449 40459 40469 40479 40489 40499 40509 40519 40529 40539 40549 40559

Addresses

Row

Row 24 Row 25 Row 26 Row 27

Row 28 Row 29 Row 30 Row 31

Row 32 Row 33 Row 34 Row Row Row Row

35 36 37 38

Row 39

Start 40560 40570 40580 40590 40600 40610 40620 40630 40640 40650 40660 40670 40680 40690 40700 40710

End

40569 40579 40589 40599 40609 40619 40629 40639 40649 40659 40669 40679 40689 40699 40709 40719

Text window begins here

Row Row Row

O

Row

3

1

2

40800 40840 40880 40920

40839 40879 40919 40959

THE 2-COLOR MODE-8 SCREEN

The Mode-8 screen offers the highest resolution of all. It uses the same 8-bit screen-data format as Modes 4 and 6 (see Fig. 4-38), the same graphics commands, and the same general 2-color scheme. Aside from the higher level of resolution, the only difference between the Mode-8 and other 2-color modes is the organization of the two color

registers.

216

°- - i-

Table 4-1 6. Starting and Ending Addresses for Each Row of the Mode-20 Screen RAM Row Row Row Row Row

0 1

2 3 Row 4 Row 5 Row 6 Row 7 Row 8 Row 9 Row 10 Row 11 Row 12 Row 13 Row 14 Row 15 Row 16 Row 17 Row 18 Row 19 Row 20

Row 21

Row 22 Row 23

Addresses Start End 40320 40329 40330 40339 40340 40349 40350 40359 40360 40369 40370 40379 40380 40389 40390 40399 40400 40409 40410 40419 40420 40429 40430 40439 40440 40449 40450 40459 40460 40469 40470 40479 40480 40489 40490 40499 40500 40509 40510 40519 40520 40529 40530 40539 40540 40549 40550 40559

Row

Flow 24 Row 25 Row 26

Row 27 Row 28

Row 29 Row 30 Row 31 Row 32 Row 33 Row 34 Row 35 Row 36 Row 37 Row 38 Row 39 Row 40 Row 41 Row 42 Row 43 Row 44

Row 45 Row 46

Row 47

Addresses

Start 40560 40570 40580 40590 40600 40610 40620 40630 40640 40650 40660 40670 40680 40690 40700 40710 40720 40730 40740 40750 40760 40770 40780 40790

End

40569 40579 40589 40599 40609 40619 40629 40639 40649 40659 40669 40679 40689 40699 40709 40719 40729 40739 40749 40759 40769 40779 40789 40799

Fig. 4-39 shows that the Mode-8 colors refer to register 1 and 2. This can cause some difficulty when working with the text-window versions, because adjustments in the graphics color will affect the luminance of the textwindow characters and both portions of the screen have the same background color. When adjusting the Mode-8 graphics color, you have two options:

SETCOLOR 1,hue,/um

and

POKE

709,16*/um + hue

Conveniently, you can PLOT that color by first execut1 statement.

ing a COLOR

218

Table 4-1 7-cont. Starting and Ending Addresses for Each Row of the Mode-22 Screen RAM Addresses

Row Row 72

Row 73 Row 74 Row 75 Row 76 Row 77

Row 78 Row 79

Row 80 Row 81

Row 82 Row 83

Msa

Start 40320 40340 403 60

40380 40400 40420 40440 40460 40480 40500 40520 40540

40339 40359 40379 40399 40419 40439 40459 40479 40499 40519 40539 40559

Addresses

Row

End

Row 84 Row 85 Row 86

Row 87 Row 88

Row 89 Row 90 Row 91 Row 92 Row 93

Row 94 Row 95

Start

End

40560 40580 40600 40620 40640 40660 40680 40700 40720 40740 40760 40780

40579 40599 40619 40639 40659 40679 40699 40719 40739 40759 40779 40799

SCREEN DATA BYTE

Lsa

an VALUE

P|XEL,0’1{2'3|4,5|i|_Ll '* '* '* '*

"

"

LEFT

0 1

RIGHT

EQu|vA|_ENT COLOR VALUE COLOR 0 COLOR 1

REG|sTEn USED 4 0

Fig. 4-38. Organization of screen data bytes for Modes 4, 6, and their

variations.

But when it comes to the background color, you must SETCOLOR or POKE the information by designating register 2; and then use a COLOR 0 statement to access it.

220

Table 4~1 8-cont. Color Register Sequences and Screen Data Bytes for 8-Pixel/ Bit Screens (Modes 4,6,8, and Their Variations) (Left ----------- Right) 0 0

Data 32 33 34 35

O

0 0 0

O

O

1

O

0 0 0 0

O

0

1

O

0

1

O

0

O

1

O

O

1

O

1

1

O

1

0

0 0

1

O

1

1

1

1

36 37 38 39

1

0

O

0

40

1

O

0

1

41

1

O

1

1

0 O

0 0 0 0 0 0 0 0 O

1 1

0 0

0 0 0

0

O

O

0

1

1

0

1

1

0 0

O

0

1

O

1

0

1

O

1

O

1

0 0

O

1

0

1

1

0

0

O

1

O

1

1

O

1

1

1

1

0

1

1

1

1

0 0 0

0 0 0

0 0

0

1

0

48 49 50

O

O

1

1

51

1

O

0

0

1

0 0

0 0 0

0 0

O O O

0 0

0

1

1 1

0 0 0

0 0

1

1

1

1

O

1

1

O

1

1

1

1

1

1

1

0 0

1

42 43 44 45 46 47

1

52 53

O

1

1

O

1

1

O

O

54

O

1

1

O

1

1

1

55

0

O

1

1

1

O

O

1

1

1

0 0

0 0

0

0 0

0

O

1

1

1

O

1

1

1

0

0

1

1

1

56 57 58 59

0 0

0 0

1

1

1

1

0

0

60

1

1

1

1

O

1

61

O

O O

1

1

1

1

1

O

1

1

1

1

1

1

0

222

1

62 63

Table 4-1 8-cont. Color Register Sequences and Screen Data Bytes for 8-Pixe|/ Bit Screens (Modes 4,6,8, and Their Variations) (Left -------~--- Right) O

0 0 0 0

0

1

0 0 0

1

1

O

0 0 0 0

0

1

1

0

1

O

1

1

O

1

1

1

1

1

1

1

1

1

O

1

1

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

O

1

O

0 0 0 0 0

0 0 0 0

Data 0 0 0 0

O O

0

0 0

0

0

1

1

O

97 98

1

1

99

1

O

0

100

1

0

1

101

1

1

0

1

1

1

O

O

0

1

1

O

1

1

1

0 0 0 0

1

1

0

0

1

1

O

1

1

96

O

102 103 104 105 106 107

0 0 0 0

1

1

1

0

108 109 110

1

1

1

1

111

1

1

O

O

O

0

1

1

1

O

1

O

1

1

1

1

1

1

0 0

0

0

0 0 0

112 113 114 115

1

1

1

0

1

1

1

1

O

1

1

1

1

1

1

1

1

1

1

1

1

1

O

1

1

0

1

1

0 0

0 0 0 0 0 0

O

0 0

1

O

1

1

0 0

0 1

1

1

0

1

1

1

1

O

O

O

0

120

1

0

1

121

1

1

O

1

0

1

1

O

1

1

1

1

1

1

1

0

O

O

1

1

1

1

1

O

1

O

1

1

1

1

1

1

O

O

1

1

1

1

1

1

224

116 117 118 119

1

122 123 124 125 126 127

Table 4-1 8-cont. Color Register Sequences and Screen Data Bytes for 8-Pixe|/ Bit Screens (Modes 4,6,8, and Their Variations) (Left ----------- Right) 1

O

1

1

O

1

O

1

1

O

1

1

O

1

0

1 1

Data

O

O

O

O

0 0

0

O

0

160

1

161

O

0 0

1

O

0

0

O

1

1

1

O

0

1

0

O

1

O

O

1

O

1

O

1

O

O

1

1

O

0

0

0

1

1

1

1

1

O

1

O

1

O

0

O

1

1

0

0

1

O

1

1

162 163 164 165 166 167

1

0 0

1

O

1

O

168 169 170

1

O

1

O

1

1

171

O

1

O

1

1

O

O

O

1

O

1

1

O

1

1

O

1

O

1

1

1

O

1

O

1

O

1

1

1

1

1

O

1

1

1

1

O

0 0

0

1

O O

O O

O

1

1

1

1

O

O

1

1

O O

O

1

0

1

1

1

0

1

1

O

1

O

O

O

180

1

1

1

O

1

O

1

181

1

O

1

1

O

1

1

O

1

O

1

1

O

1

1

1

1

O

1

1

1

O

O

O

1

O

1

1

1

O

O

1

1

O

1

1

1

O

1

O

1

O

1

1

1

O

1

1

1

O

1

1

1

1

O

0

O

1

1

1

1

1

O

1

1

O

1

1

1

1

1

O

188 189 190

1

O

1

1

1

1

1

1

191

1

0 0

1 1

1

226

1

172 173 174 175 176 177 178 179

182 183 184 185 186 187

Table 4-1 8-cont. Color Register Sequences and Screen Data Bytes for 8-Pixe|/ Bit Screens (Modes 4,6,8, and Their Variations) (Left ---------~- Right)

Data

0 0 0

0 0

0 0

0 0

O

O

1

1

O

0

0

O

1

1

227

1

1

O

O

0

228

1

1

1

1

1

1

0

229 230

1

1

1

0 0 0

0

1

0 0 0 0

1

1

1

1

1

231

1

1

1

O

1

O

O

1

1

O

1

0

0

1

O

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1 1

0 1

1

224 225 226

1

O

1

0

1

O

1

1

232 233 234 235

0

1

1

236

1

1

1

0

0 0

0

O

1

1

1

0

237 238

1

1

O

1

1

1

1

239

1

1

1

1

O

1

1

0 0

240

1

1

241

1

1

1

1

1

1

1

1

0 0 0 0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

O

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1 1

228

0 0

0 0 0

1

1

0

1

1

242 243

0 0

0

244

1 1

1

O

1

1

1

247

0 0

0 0

0

248

1

249

1

O

1

250

1

1

0

0

1

1

251

1

1

1

1

1

1

1

1

0 0

1

1

1

1

1

1

0

1

1

1

1

1

1

1

0 0 0

1

1

O 1

245 246

252 253

254 255

3

O

QQ

fiis llll EE 3

U,

,_

llll llll llll llll llll llll llll llll llll IIII Illl llll llll llll llll llll llll llll llll llll llll |||| :nun llll :ilu llll llll llll llIl llll llll llll n||| llll llll |||| llll llll llll

”

/ O

O

3 Qi' _

Mousamdvus

ZW

CV

(0

I0

F) F) FJ

v-

F) U1 CV

N (V ID

N C9

N EG

2 l\ vI0 vF) Q-

vvU3

|\ ID

F) Q-

O

i- ;

Table 4-1 9. Starting and Ending Addresses for Each Row of the Mode-8 Screen RAM Row Row 0 Row 1 Row 2 Row

3 4 5 6 7 Row 8 Row 9

Row Row Row Row

Row 10 Row 11 Row 12 Row 13 Row 14 Row 15 Row 16 Row 17 Row 18 Row 19 Row 20

Row Row Row Row

21

22 23 24

Row 25

Row 26 Row 27 Row 28 Row 29 Row 30

Row 31 Row 32 Row 33 Row 34 Row 35

Row 36 Row 37 Row 38 Row 39

Row 40 Row 41

232

Addresses Start End 33104 33143

33144 33184 33224 33264 33304 33344 33384 33424 33464 33504 33544 33584 33624 33664 33704 33744 33784 33824 33864 33904 33944 33984 34024 34064 34104 34144 34184 34224 34264 34304 34344 34384 34424 34464 34504 34544 34584 34624 34664 34704 34744

33183 33223 33263 33303 33343 33383 33423 33463 33503 33543 33583 33623 33663 33703 33743 33783 33823 33863 33903 33943 33983 34023 34063 34103 34143 34183 34223 34263 34303 34343 34383 34423 34463 34503 34543 34583 34623 34663 34703 34743 34783

Row Row 42 Row 43 Row 44 Row 45 Row 46 Row 47 Row 48 Row 49 Row 50 Row 51 Row 52 Row 53 Row 54 Row 55 Row 56 Row 57 Row 58 Row 59 Row 60 Row 61 Row 62 Row 63 Row 64 Row 65 Row 66 Row 67 Row 68 Row 69 Row 70 Row 71 Row 72 Row 73 Row 74 Row 75 Row 76 Row 77 Row 78 Row 79 Row 80 Row 81 Row 82 Row 83

Addresses

Start 34784 34824 34864 34904 34944

34984 35024 35064 35104 35144 35184 35224 35264 35304 35344 35384 35424 35464 35504 35544 35584 35624 35664 35704 35744 35784 35824 35864 35904 35944 35984 36024 36064 36104 36144 36184 36224 36264 36304 36344 36384 36424

End

34823 34863 34903 34943 34983 35023 35063 35103 35143 35183 35223 35263 35303 35343 35383 35423 35463 35503 35543 35583 35623 35663 35703 35743 35783 35823 35863 35903 35943 35983 36023 36063 36103 36143 36183 36223 36263 36303 36343 36383 36423 36463

--- _-li

Table 4-20. Starting and Ending Addresses for Each Row of the Mode-24 Screen RAM Addresses

Row Row Row Row Row Row Row Row Row Row Row Row Row Row Row

Row Row Row

Row

O 1

2 3 4 5 6 7 8 9

10 11

12 13 14 15 16 17 18 19

Row Row Row 20

Row 21 Row Row Row Row

Row Row Row Row Row Row Row Row Row Row

236

22 23 24 25 26 27 28 29 30 31

32 33 34 35

Start

End

33104 33144 33184 33224 33264 33304 33344 33384 33424 33464 33504 33544 33584 33624 33664 33704 33744 33784 33824 33864 33904 33944 33984 34024 34064 34104 34144 34184 34224 34264 34304 34344 34384 34424 34464 34504

33143 33183 33223 33263 33303 33343 33383 33423 33463 33503 33543 33583 33623 33663 33703 33743 33783 33823 33863 33903 33943 33983 34023 34063 34103 34143 34183 34223 34263 34303 34343 34383 34423 34463 34503 34543

Row

Row Row Row Row Row

36 37 38 39 40

Row 41 Row 42 Row 43 Row 44 Row 45

Row 46 Row 47

Row 48 Row 49 Row 50

Row 51 Row 52

Row 53 Row 54 Row Row Row Row Row Row Row Row Row Row Row Row Row Row Row Row Row

55 56

57 58 59 60 61

62 63 64 65 66 67 68 69 70 71

Addresses

Start

End

34544 34584 34624 34664 34704 34744 34784 34824 34864 34904 34944 34984 35024 35064 35104 35144 35184 35224 35264 35304 35344 35384 35424 35464 35504 35544 35584 35624 35664 35704 35744 35784 35824 35864 35904 35944

34583 34623 34663 34703 34743 34783 34823 34863 34903 34943 34983 35023 35063 35103 35143 35183 35223 35263 35303 35343 35383 35423 35463 35503 35543 35583 35623 35663 35703 35743 35783 35823 35863 35903 35943 35983

DOS RAM USAGE: 1792-10879 If DOS is not active in the ATARI system, BASIC programming information will normally begin at address 1792. Booting DOS, however, fills at least 9088 bytes of system RAM with DOS and file-management programming. As indicated in Chart 8-5, that programming begins at address 1792 and extends to 10879, or to the current LOMEM setting. That being the case, BASIC programming picks up from the end of the DOS area.

Chart 8-5. DOS Usage of System RAM: 1 792-1 0879. or LOMEN

$0700-$12FF 1792-4863 File-management RAM area; 3072 bytes.

$1300-$267F

4864-9855

DOS operating system RAM area; 4992 bytes.

$2680-$2A7F 9856-10879 DOS I/O buffers; 1024 bytes.

BASIC ROM AREA:

40960-49151

The ATARI BASIC cartridge overlays any RAM that might be present in the area that it uses. Chart 8-6 offers a map of that section of the memory map.

Chart 8-6. BASIC ROM AREA: 40960-491 51 $AO00-$A04C

40960-41036

$A04D-$A05F

41037-41055

BASIC cold start routine.

BASIC warm start routine.

338

Chart 8-6-cont. BASIC ROM Area: 40960-491 51 SB916-$B9B6 47382-47542 Error-handling routines. $B9B7-SBA74

47543-47732

Graphics-handling routines. SBA75-SBDA4

47733-48548 l/O-handling routines. SBDA5-SBFF9

48549-49145

Trigonometric function routines.

SBFFA-SBFFB 49146-49147 Left cartridge start address. $BFFC

49148

Left-cartridge installed byte: 0 = cartridge installed nonzero = cartridge not installed SBFFD-49149 Purpose is unclear. $BFFE-$BFFF

49150-49151

Cartridge initialization address; jump point after executing SYSTEM reset under BASIC.

HARDWARE I/O ROM AREA: 53248-55295 Chart 8-7 gives an overview of the hardware I/O ROM area. This is regarded as ROM only in a casual sense. Some addresses are devoted to RAM-like read/write operations; the practical difficulty, from a programmer’s point of view, is that such areas are available for write operations only during the screen’s vertical retrace interval.

Chart 8-7. Hardware I/O ROM Area: 53248-55295 SDOOO-SDOFF $D100-$D1 FF

$D200-SDZFF $D300-$D3FF $D400-$D5FF $D600-$D7FF

340

53248-53503 53504-53759 53760-54015 54016-54271 54272-54783 54784-55295

CTIA (or GTIA)

Unused POKEY PIA

ANTIC

Unused

Chart 8-8-cont. CTIA (or GTIA) I/O Map Detail: 53248-53503 SDOOD

Shape

of

53261 player O/player

GRAFPO/P1 PL

1

player collision.

53262 GRAFP1/P2PL Shape of player 1/player 2 player collision. SDOOE

53263 GRAFP2/P3PL Shape of player 2/player 3 player collision. $DO0F

$D01O

Shape

53264

of

player 3/joystick

SDO11

Shape of

all

O

trigger.

53265 missiles/joystick

GRPFP3/TRIGO GRAFM/TRIG1

1

trigger.

$DO12 53266 COLOPMO/TRlG2 Color of player and missile O/joystick 2 trigger.

$D013

53267

COLOPM1/TRlG3

Color of player and missile 1/joystick 3 trigger.

SDO14 53268 COLOPM2/PAL Color of player and missile 2/European TV sync. flag. SDO15 53269 Color of player and missile 3.

COLOPM3

$DO16 53270 Color of playfield 0.

COLPFO

$D017

53271

COLPF1

$DO18 53272 Color of playfield 2.

COLPF2

SDO19 53273 Color of playfield 3.

COLPF3

$DO1A 53274 Color of background.

COLBK

Color of playfield 1.

$DO1 B

53275

PRIOR

Figure priority-select; determines whether located behind or in front of another.

342

a

figure is to be

Chart 8-9-cont. POKEY Map Detail: 53760-5401 5 SD204 53764 Audio voice 3 frequency/paddle

2

AUDF3/POT4 setting.

$D205 53765 AUDC3/POT5 Audio voice 3 volume and distortion/paddle 5 setting.

$D206 53766 AUDF4/POT6 Audio voice 4 frequency/paddle 6 setting. SD207 53767 AUDC4/POT7 Audio voice 4 volume and distortion/paddle 7 setting.

$D208 53768 AUDCTL/ALLPOT Audio voice master control/ all paddles. $D209 53769 STIMER/KBCODE Start POKEY timers/ keyboard latch. SD20A

53770

Random-number counter/register. $D20B 53771 Read paddles flag. $D20C Not used. $D2OD

RANDOM

POTGO

53772

53773 Serial I/O register.

SEROUT/SERIN

$D20E 53774 IRQEN/IROST Interrupt request enable and interrup I status FSQUBS( register. $D20F

53775 SKCTL/SKSTAT Serial control and status register; includes keyboard debounce, keyboard scanning, and serial port mode cont rol $D21O-$D2FF 53776-54015 Duplicate of $D200-$D2OF (53760-53775)

344

Chart 8~11-cont. ANTIC Map Detail: 54272 54303 SD405 54277 Vertical-scroll enable. SD406 Unused.

VSCROL

54278

$D407 54279 PMBASE Most-significant byte of the player/missile base address SD408

Unused. $D409

54280 54281

Text character bit map base address. $D4OA 54282 Wait-for-horizontal sync flag. $D4OB

54283 Vertical-scan line counter. $D4OC

VCOUNT PENH

54285

PENV

54286

NMIEN

Vertical position of light pen. $D4OE

WSYNCH

54284

Horizontal position of light pen. $D4OD

CHBASE

Enable nonmaskable interrupt.

$D4OF 54287 NMIRES/NMIST Clear interrupt-request, reset any nonmaskable interrupts. and return current interrupt status.

$D41O-$D41F 54288-54303 Duplicate of $D400-$D4OF 54272-54287

OPERATING SYSTEM ROM AREA:55296-65535 The uppermost section of the ATARI memory map is devoted to ROM operations for the operating system, itself. This section is common to both the 800 and 400 systems, and it is used whether a BASIC cartridge is installed or not.

346

Chart 8-1 2-cont. Operating System ROM Area: 55296-65535 SFOE3-$F3E3 61667-62435 Monitor handler routines. $F3E4-SFFFF 62436-65535 Display and keyboard handler routines.

348

Table 9-1. Summary of the 6502 Instruction Set as Organized by Op Codes Hex

Op code $00

Dec Op

0

BRK

1

ORA

$01

$02 $03 $04 S05 S06 $07 S08 $09 SOA SOB SOC SOD SOE $OF

S10 $11 $1 2 S1 3 $14 $15 $16 $17

$18 $19 $1A $1 B

$1C $1 D $1 E $1 F

350

_

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2

3 4 5

6 7 8 9 10

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PHP ORA ASL

1 1

12 13 14 15 16 17 18 1 9

ORA ASL

implied (indirect, x) not used not used not used zero page zero page not used implied

immediate accumulator not used not used absolute absolute not used

BPL

relative

ORA

(indirect),Y not used not used

20

JSR

21

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zero page,X zero page,X not used

CLC ORA

implied absolute,Y not used not used not used absolute,X absolute,X not used

22

23 24 25 26

27 28 29 30 31

ORA ASL

Table 9-1 -cont. Summary of the 6502 Instruction Set as Organized by Op Codes Op Code

Hex

OpDec Code

SCO SC1 SC2

SC6 SC7

192 193 194 195 196 197 198 199

SC8 SC9

201

SC3 SC4 SC5

SCA SCB SCC SCD SCE SCF

202 203

SDO SD1

208 209

SD2 $D3 SD4 SD5 SD6 SD7 SD8 SD9 SDA SDB SDC SDD SDE SDF

356

200

204 205

206 207

210 21

Mnemonic CPY

immediate

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(indirect,X) not used not used

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implied

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1

212 213

214 215 216

217 218

CMP DEC

CLD

CMP

219 220 221

222 223

CMP DEC

immediate implied not used

absolute absolute absolute not used

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BNE Branch

on result not zero

Operation: Branch

if Z=O

Status register

(P)

NZCIDV Addressing Assembly Language Mode Format Relative

BPL Branch

BNE

Oper

Op Code

Hex

Dec Op Code

DO

208

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on result plus

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Status register

(P)

NZCIDV Addressing Mode

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BRK

Assembly Language Format BPL

Oper

Op Code

Hex

Dec Op Code

10

16

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Forced break

Operation: Interrupt, PC+21PI Status register

(P)

NZCIDV ___-|__ Addressing Mode

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362

Assembly Language Format BRK

Hex

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Bytes 1

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Operation:

accumulator 1 bit to left L‘]l§ElE]El]E]

Status register Z *

*

Addressing Mode

Accumulator Zero Page Zero Page,X Absolute Absolute,X

Assembly Language Format ROL ROL ROL ROL ROL

C

_

Dec

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2A

Oper Oper,X Oper Oper,X

V

_

Hex

Op Code

A

(P)

D

I

*

C

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62

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Operation

EEBHEHE

C

Status register

Addressing Mode Accumulator Zero Page Zero Page,X Absolute Absolute,X

374

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A

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Oper Oper,X Oper Oper,X

(P)

N

Z

C

I

D

~k

-k

1-

_

_

V

Hex

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6A

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1

10

126

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-

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(P)

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N

Lrngutge

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Implied

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D

I

V

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W

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1

decimal arithmetic mode

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(P)

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N

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Z

C

Hex

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D

I

V

Dec Op Code

Bytes

248

1

Set disable interrupt flag 1 ->I

Operation:

Status register

(P)

NZCIDV ___-|__ Addressing Mode Implied

376

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78

Dec Op Code 120

Bytes 1

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-

X

Status register N *

Addressing Mode

TAX

C

I

D

V

'A'

_

_

_

_

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-

Y

(P)

Z

Assembly Language' Hex Format Op Code

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TAY

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X

I

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1

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Implied

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TAY

A8

Transfer stack pointer to

Operation:

Hex

Op Code

S

-

X

Dec Op Code 168

Bytes 1

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Status register (P)

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378

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Hex

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L LS LS LS LS

LOS

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60S 80S

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J.X3N

SAE

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INOI)

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d0d dOiS NDH NUDLBH

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BOS CIOS

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suaqol pueunuog sua>|o_|_ puewwog sua>|oj_ |eLugaapexa|.|/|ewg:JaC| .ngaql pue SP-'°N\'\9)l PUUWWUO OISVS II:lV.|.V 'L'8 9Iq9l

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zzs Lzs

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soo

v LS

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J.-1HJ.3

>LvN

n-win

NAS

A-'luis

ala

/v\-'Lum

Nvo

x-‘Lula

wa

A-'Lula

'ans

z-ww

asa

asa/asa

sa

--1u1:>/asa

S9

=~'|uL:>/asa

3 LS

_,_

su

+-‘Lula/asa

:ns

if;

sn

.-1L-no/asa

(aoeds)

Jag aoedg

L;_J

zoo

a-wir)

s-mio

|o.|1uo31o (s)a>|o.|;sAa)|

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035

Cl

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15

; ’1

Li FTW gur

0

a

LS

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vLs 6Ls 8Ls LLs

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u.§.

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a.|eq3

6L 8L LL 9L

§L VL

SL

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OL

69 89 L9

99 99 V9

9°

upon

WOH

mg 1e;:>amq3 |eu.|a;u| 'N-'99-Z'O 9Iq9l

9.W919AS IHVLV 9|-ll

Table C-2-cont. The ATARI System’s Internal Character Set Code

ROM Map Addresses

Character

Decimal

Hexadecimal

Start

End

Start

End

$50

57984

57991

SE280

SE287

81

$51

57992

57999

SE288

$E28F

82

$52

58000

58007

SE290

SE297

83

$53

58008

58015

SE298

$E29F

84

$54

58016

58023

$E2A0

$E2A7

85

$55

58024

58031

$E2A8

$E2AF

86

$56

58032

58039

$E2B0

$E2B7

87

S57

58040

58047

SEZB8

$E2BF

88

$58

58048

58055

$E2C0

$E2C7

89

$59

58056

58063

SE2C8

$E2CF

90

$5A

58064

58071

$E2D0

SE2D7

91

$58

58072

58079

$E2D8

$E2DF

92

$5C

58080

58087

SE2E0

$E2E7

93

$5D

58088

58095

SE2E8

$E2EF

94

$5E

58096

58103

$E2F0

$E2F7

95

$5F

58104

58111

$E2F8

$E2FF

Dec

Hex

80

422

!ZV

Pua

wus

:wa

61183

ooeas

Loses

aosas

aosas

96189

01896

ueas

S7189

8L!3$

911699

19189

ozeas

Lzsas

69189

azsas

azsas

A9189

ossas

Leeas

9L189

aesas

aeeas

68189

ovsas

Lveas

118189

16189

sveas

avsas

Z6L89

66189

09839

1.98219

LOZ89

89838

9969s

8OZ8S

91z89

09838

Lssas

91289

ezz89

8969s

=19sas

oLsas

Maas

8Lsas

#sas

6ez89 18z89

ii

VZZSQ

C*

z8z89

OOZ89

r__

o11

39S

111

ass

801

39S

‘{

601

69s

N

'pg

§"`

89S

v9s

LOL

901

.

|ewg:>epaxe|.|

LZl89

9L189

69s

If L;

89s

901 VOL

86

z9s

66

69s

.Zi

oo1

V98

91

LOL

99s

itJ

09189

o Ll!

89189

z9189 VVLBG

98189

I

w

"1

8Zl89

oz189

-2

z 1 L89

.|310B¢lBI.|Q

Les 99$

19s

09S

was

|su|g:>aq

X911

Jewemqg

sassezppv dew wgg

wg

5.'-1191558 IHVLV 9\|.|.

601

zo1

L6

96

390

9900

|eu1a1u|

'1U°°_Z°O alqel

Table

C-2-cont. The ATARI System's Internal Character Set

ROM Map Addresses

code Character Dec 12

1

Hex

$70

{:

Hexadecimal

Decimal

Start

End

Start

End

58240

58247

SE380

SE387

58248

58255

SE388

$E38F

{_-_ 113

$71

114

$72

‘{'°

58256

58263

SE390

SE397

115

$73

3 L_; ._

58264

58271

SE398

$E39F

116

$74

'L

58272

58279

$E3A0

$E3A7

17

$75

1_1

58280

58287

$E3A8

$E3AF

118

$76

‘-,J

58288

58295

$E3B0

$E3B7

119

$77

5.-'J

58296

58303

$E3B0

$E3BF

120

S78

:;.;:

58304

5831

$E3CO

$E3C7

121

$79

:ii

58312

58319

$E3C8

$E3CF

122

$7A

E

58320

58327

$E3DO

$E3D7

123

$78

58328

58335

$E3D8

$E3DF

124

$70

58336

58343

$E3E0

$E3E7

125

$70

58344

58351

$E3E8

$E3EF

126

$7E

58352

58359

$E3F0

$E3F7

127

$7F

59360

58367

$E3F8

$E3FF

1

='Z1_

"1 F"`1

I

424

‘T §

E

4 *

1

SZ?

°sapo9

amp ;o aauanbas |e:>g1amunu amp O1 Sugpmoae pazgue8.|o sg 1; 1nq 'uopeu.uo;ug amues amp s1sg| 9-Q a|qel °sapoJ |eu|g;> -apexaq pue |emug3ap Bugpuodsauoa pue a>|onsAa>| amp uopeuuo;ug amp 1sg| g-(1 m|8no.|mp L-Q sa|qe1

gU!M0l..|S /(q

'mua1s/(S |}|Vj_V amp

U!l..|1!M pa1eJaua8 Apuanbasqns axe zemp sapoa pue sa>|ons -/(a>| asomp 1sg| a.|am| UMOL|S sa|qe1 am|j_ °uop:>e p1eoqAa>| s1uasaJdaJ xemp apoa 1a1oeJem|9 sa:>npoJd sa>|oJ1s ;o uopeugqmuoa alepdmdde pue a>|oJ1sAa>| Ma/mg

zemp

me

-Aa>|

SGPOJ P1P°°|K=>>| luvmv (1

xgpuaddv

-li

Table D-1. Keystrokes and Corresponding Key Codes (Single-Key Operations) Key

Space Bar "

# $

% & ' ( )

*

+ .

-

/ O 1

2 3 4 5 6 7 8

426

Code Dec

Hex

32 33

$20

34 35 36 37 38 39 40

$22 $23 $24 $25 $26 $27 $28 $29

41

42 43 44 45 46 47 48 49 50 51

52

53 54 55 56

$21

$2A $2B $2C $2D $2E $2F

$30

Key

9 ;

< = >

Code

Dec 57

$39

58

S3A $3B

59

60 61

?

62 63

@

64

A

65

B C

66 67 68

D

E

69

F

70

G

71

H

72 73

I

$31

J

$32 $33 $34 $35 $36 $37 $38

K L

M N

O P O

Hex

74 75 76 77 78

79 80 81

$3C $3D $3E $3F $40 $41 $42 S43 $44 $45 $46 $47 $48 $49 $4A $4B $4C $4D $4E $4F

$50 $51

LZ?

36s 365

oss ses aes

GSL

8§l LSL L

99

L

99

VZL

oLs

LzL

'a Ls

9zL 9zL

cms

BLS

LZL

3Ls

ws 6Ls aLs

as 9Ls 9Ls vLs

us us LLS

oLs

39s

zzL LzL

ozL 61 L

8l ll

L

L

91

L

9 ll bl

L

9 Ll

z

Ll

LLL

6oL 8oL

39s

oL

39S

oss

L

seq __-____ xaH

9P°O

13s

an

Lu3sN| 313130 Nun13u

avi

s >|:>va HVETO

:>s3

ass

v9s 69s 895 L9s 99$

sas vss ass z9s

2 A X

M A L1

1

S 1

b d

0 U

w L

Ae)|

L9s

39s 39s

oss ass ass vss ess ass Lss 99s

1.0L

90L 9oL

ess vss ass zss

xa|.|

>L

I

L

ZOL

6

soL

u

VOL

P

ooL

9

LoL

es as L6 S6

vs as ze L6

oe

68

as L8

98

illl sa va

as za

aaq

°P°:J

(suogmxadg Aa)|-a|6ugg) sapog Aa)| Bugpuodsauog pus sa>|onsAa)| °1uo:J- |,-Q

v q 2

'

I

/ 1

z A

x M

/\

n 1

s

u Aa)|

a|qe_|_

Table D-2. Keystrokes and Corresponding Key Codes (CTR L-Key Operations) Code

Key CTRL-, CTRL-A CTRL-B CTRL-C CTRL-D CTRL-E CTRL-F

CTRL-G CTRL-H CTRL-I CTRL-J CTRL-K CTRL-L CTRL-M CTRL-N CTRL-O CTRL-P CTRL-O CTRL-R

Code

Ke

Dec

Hex

y

Dec

Hex

0

$00 $01

19

1

2 3 4 5 6 7 8 9

$02 $03 $04 $05 $06 $07 $08 $09

CTRL-S CTRL-T CTRL-U CTRL-V CTRL-W CTRL-X CTRL-Y

$13 $14 S15 S16 S17 $18 $19

10

SOA SOB SOC SOD SOE SOF

11

12 13 14 15 16 17 18

$10 $11

$12

CTR L-Z CTRLCTRLCTRLCTRLCTRL-_ CTRL-;

CTRL-2 CTRL-3 CTRL-DELETE CTRL-INSERT

20 21

22 23 24 25 26 28 29 30

$1 A $1 C

S10 $1 E

31

S1 F

96 123 253 155 254 255

$60

$78 SFD

S98 SFE SFF

operations that are not indicated here will generate the same codes as their non-CTRL counterparts. NOTE: CTRL-key

428

GZL’

DOS SGS VOS

6O$ 8OS

OZZ

6LZ 8 LZ L LZ

DVS

X

BVS OVS

Z ]

SVS VVS

M S W >| 3 O @ < 8 9

' ) ‘8 Z°'IH.L3 A"lU.|.3 X‘1¥:|J.3 M'1\:|l3 /\"|U.LfJ S"l!:|.L3 )|"\U.|.1`)

O'1l:|.|.D |ousAa)| -7-Q a|qe_|_

Table D-4-cont. Keystrokes and Corresponding Key Codes Arranged With Key Codes in Numerical Order C0d6

066

Hex

86 87 88 89 90

$56 $57 $58 $59

91

92 93 94 95 96 97 98 99 100

101

102 103 104 105 106 107 108 109 110

1 1 1

15 16 17

118 119 120 121

122 123 124 125 126 127 128

432

X

131

Y

132 133 134 135 136 137 138 139 140

\

1

_

CTRL-_

$61

a

$62 $63

b

$64 $65 $66 $67 $68 $69 $6A

$68 $6C

$60 $6E

$70

114

129 130

[

$60

$71

$72 $73 $74 $75 $76 $77 $78 $79 $7A

$78 $70

$7D

s7E $7F $80

Code 066 Hex

W Z

$5E $5F

$61=

13

v

$58 $50 $50

11

1

°Y

$5A

112

1

K

c

d

e f 9 h j

k I

m n 0 p q r

s 1

u v

w x y 1

CTRL-; CLEAR BACK s TAB CTRL-,

141

142 143 144 145 146 147 148 149 150 151

152 153 154 155 156 157 158 159 160 161

162 163 164 165 166 167 168 169 170 171

$81

$82 $83 $84 $85 $86 $87 $88 $89 $8A

$88

sac

$80 $8E $8|=

$90 $91

$92 $93 $94 $95 $96 $97 $98 $99 $9A

$98 $90 $90 $9E

$9|= SAO $A1

SA2 $A3 SA4 $A5 $A6 SA7 $A8 $A9 SAA SAB

K

°y

CTRL-A CTRL-8 CTRL-C CTRL-0 CTRL-E CTRL-P CTRL-G CTRL-H CTRL-I CTRL-.1 CTRL-K CTRL~L CTRL-M CTRL-N cTRL~0 CTRL-P CTRL-Q CTRL-R CTRL-S CTRL-T cTRL~u CTRL-V CTRL-W CTRL-X CTRL-Y CTRL-Z RETURN and CTRL 3 DELETE INSERT TAB

SET

space

!

"

#



%



'

$

&

( )

*

+

SH’

lH3SN|'1HlC) 313130-1uLo z-1u1:> I

2

sas

ssz vsz esz zsz LSZ

osz GVZ

9!Z

:Jas

sez

ovz 6ez

oss das aas

Las



1



A



~\

X

n



w

u |

L

>| F

L

Q

q 2



- P°w

6l M08 8l M08 Ll M08 9L M08 9 L M08 7 L M08 8L M08

Zl M08 L L M08 OL M08 6 M08 8 M08 L M08 9 M08 9 M08 7 M08 8 M08 Z M08 I, M08 0 M08

Mau

OISVB

luvlv 104 Svswppv °1n|°Sqv 'z-a

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