ATARI 400/800 computer BASIC reference manual

Below you will find brief information for computer 400/800. The computer 400/800 is a personal computer system capable of executing commands in BASIC. It has a unique set of graphic capabilities and a library of built-in functions.

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ERROR CODES

ERROR

CODE ERROR CODE MESSAGE

Memory Insufficient

Value Error

Too Many Variables

String Length Error

Out of Data Error

Number greater than 32767

Input Statement Error

Array or String DIM Error

10 Argument Stack Overflow

11 Floating Point Overflow/

Underflow Error

Line Not Found

No Matching FOR Statement

Line Too Long Error

GOSUB or FOR Line Deleted

RETURN Error

Garbage Error

Invalid String Character

Note: The following are INPUT/OUTPUT errors that result during the use of disk drives, printers, or other accessory devices. Further information is provided with the auxiliary hardware.

134

135

136

137

138

139

140

141

128

129

130

131

132

133

LOAD program Too Long

Device Number Larger

LOAD File Error

BREAK Abort

IOCB

Nonexistent Device

IOCB Write Only

Invalid Command

Device or File not Open

BAD IOCB Number

IOCB Read Only Error

EOF

Truncated Record

Device Timeout

Device NAK

Serial Bus

Cursor Out of Range

ERROR

CODE ERROR CODE MESSAGE

142

143

144

145

146

147

160

161

162

163

164

165

166

167

168

169

170

171

Serial Bus Data Frame Overrun

Serial bus data frame checksum error

Device done error

Read after write compare error

Function not implemented

Insufficient RAM

Drive number error

Too many OPEN files

Disk full

Unrecoverable system data I/O error

File number mismatch

File name error

POINT data length error

File locked

Command invalid

Directory full

File not found

POINT invalid

For explanation of Error Messages see Appendix B.

BASIC

REFERENCE

MANUAL

)IL

ATARI®

A Warner Communications Company

Every effort has been made to ensure that this manual accurately documents the operation of the ATARI 400 and the ATARI 800 computer. However, due to the ongoing improvement and update of the computer software, Atari, Inc. cannot guarantee the accuracy of printed material after the date of publication, nor can Atari accept responsibility for errors or omissions. Revised manuars and update sheets will be published as needed and may be purehased by writing to:

Atari Software Support Group

P.O. Box 427

Sunnyvale, CA 94086

Printed in USA

PREFACE

1 GENERAL INFORMATION

Terminology

Special Notations Used In This Manual

Abbreviations Used In This Manual

Operating Modes

Special Function Keys

Arithmetic Operators

Operator Precedence

Built-In Functions

Graphics

Sound and Garnes

Wraparound and Keyboard Rollover

Error Messages

2 COMMANDS

BYE

CONT

END

LET

LIST

NEW

REM

RUN

STOP

3 EDIT FEATURES

Screen Editing

Contröl (CTRL) Key

Shift Key

Double Key Functions

Cursor Control Keys

Keys Used With CTRL Key

Keys Used With Shift Key

Special Function Keys

Break Key

Escape Key

4 PROGRAM STATEMENTS

FOR/NEXT/STEP

GOSUB/RETURN

GOTO

IF/THEN

Contents

lii

vii

7

IV COntents

ON/GOSUB

ON/GOTO

POP

RESTORE

TRAP

5 INPUT/OUTPUT COMMANDS

Input/Output Devices

CLOAD

CSAVE

DOS

ENTER

INPUT

LOAD

LPRINT

NOTE

OPEN/CLOSE

POINT

PUT/GET

READ/DATA

SAVE

STATUS

XIO

Chaining Programs

6 FUNCTION LIBRARY

Arithmetic Functions

ABS

CLOG

EXP

INT

LOG

RND

SGN

SQR

Trigonometric Functions

ATN

COS

SIN

DEG/RAD

Special Purpose Functions

ADR

FRE

PEEK

POKE

USR

7 STRINGS

ASC

CHR$

LEN

STR$

VAL

String Manipulations

8 ARRAYS AND MATRICES

DIM

CLR

9 GRAPHICS MODES AND COMMANDS

GRAPHICS

Graphics Modes

Mode 0

Modes 1 and 2

Modes 3, 5, and 7

Modes 4 and 6

Mode 8

COLOR

DRAWTO

LOCATE

PLOT

POSITION

PUT/GET

SETCOLOR

XIO (Special Fill Application)

Assigning Colors to Text Modes

Graphics Control Characters

10 SOUND AND GAME CONTROLLERS

SOUND

PADDLE

PTRIG

STICK

STRIG

11 ADVANCED PROGRAMMING TECHNIQUES

Memory Conservation

Programming In Machine Language

APPENDIX A BASIC RESERVED WORDS

A-1

APPENDIX B ERROR MESSAGES

B-1

APPENDIX C ATASCII CHA.RA.CTER SET

WITH DECIM.AL/

HEXADECIMAL LOCATIONS c-i.

APPENDIX D ATARI 400/800

MEMORY MAP

D-1

47'

Contents V

vi Contents

APPENDIX E DERIVED FUNCTIONS

APPENDIX F PRINTED VERSIONS OF

CONTROL CHARACTERS

APPENDIX G GLOSSARY

APPENDIX H USER PROGRAMS

APPENDIX I MEMORY LOCATIONS

INDEX

F-1

G-1

11-1

I-1

117

PREFACE

This manual assumes the user has read the Atari BASIC — A Seif-Teaclang

Guide or some other book on BASIC. This manual is not intended to "teach"

BASIC. lt is a reference guide to the commands, statements, functions, and special applications of Atari® BASIC.

The programs and partial programming examples used in this manual are photostats oflistings printed on

the Atari 820TM Printer. Some of the special Sym- bols

in the Atari character set do not appear the same on the printer; e.g., the clear screen symbol appears as a " ". The examples in the text were chosen to illustrate a particular function — not necessarily "good" programming techniques.

Each of the sections contains groups of commands, functions, or statements dealing with a particular aspect of Atari BASIC. For instance, Section 9 contains all the statements pertaining to Atari's unique graphics capabilities. The appendices include quick references to terms, error messages, BASIC keywords, memory locations, and the ATASCII character set.

As there is no one specified application for the Atari Personal Computer System, this manual is directed at general applications and the general user. Appendix H contains programs that illustrate a few of the Atari system's capabilities.

Preface vii

GENERAL

INFORMATION

This section explains BASIC terminology, special notations, and abbreviations used in this manual, and the special keys on the ATARI 4QQTM and ATARI 800T 1

Personal Computer Systems keyboard. lt also points to other sections where

BASIC commands deal with specific applications.

TERMINOLOGY

BASIC:

Beginner's All-purpose Symbolic Instruction Code.

BASIC Keyword:

Any reserved word "legal" in the BASIC language. May be used in a statement, as a command, or for any other purpose. (See Appendix A for a list of all "reserved words" or keywords in ATARI BASIC.)

BASIC Statement:

RUN.

Usually begins with a keyword, like

LET, PRINT,

Constant:

A constant is a value expressed as a number rather than represented by a variable name. For example, in the statement X = 100, X is a variable and

100 is a constant. (See

Variable.)

Command String:

Multiple commands (or program statements) placed on the same numbered line separated by colons.

Expression:

An expression is any legal combination of variables, constants, operators, and functions used together to compute a value. Expressions can be either arithmetic, logical, or string.

Function:

A function is a computation built into the computer so that it can be called for by the user's program. A function is

NOT

a statement; it is part of an expression. lt is really a subroutine used to compute a value which is then

"returned" to the main program when the subroutine returns. COS (Cosine),

RND

(random),

FRE

(unused memory space), and

INT

(integer) are examples of functions. In many Cases the value is simply assigned to a variable (stored in a variable) for later use. In other cases it may be printed out on the screen immediately. See Section 6 for more on functions. Examples of functions as they might appear in programs are:

113 PRINT RNE( )

11.3 Xr--.1E1F1+012( 45

(print out the random number returned)

(add the value rereturned to 100 and store the total in variable X)

General Information 1

Generalbyönnation

Logical Line: A logical line consists of one to three physical lines, and is terminated either by a

RETURN

or automatically when the maximum logical line limit is reached. Each numbered line in a BASIC program consists of one logical line when displayed on the screen. When entering a line which is longer than one physical line, the cursor will automatically go to the beginning of the next physical line when the end of the current physical line is reached. If

RETURN

is not entered, then both physical lines will be part of the same logical line.

Operator: Operators are used in expressions. Operators include addition ( + ),

subtraction ( -)‚ multiplication ( * division (/), exponentiation

(A),

greater than

(›), less than (<)‚ equal to ( = greater than or equal to (> .), less than or equal to

(< = ), and not equal to (< >). The logical keywords AND, NOT and OR are also operators. The + and - operators can also be used as unary operators; e.g., - 3.

Do not put several unary operators in a row; e.g.,--3, as the computer will interpret it incorrectly.

Physical Line:

One line of characters as displayed on a television screen. string:

A string is a group of characters enclosed in quotation marks.

"ABRACADABRA" is a string. So are "ATARI MAKES GREAT COMPUTERS" and "123456789". A string is much like a constant, as it too, may be stored in a variable. A string variable is different, in that its name must end in the character $. For example, the string "ATARI 800" may be assigned to a variable called A$ using (optional)

LET

like this:

12 LET AS=HATARI

12 A$="ATARI

202"

222"

(note quotation marks)

(LET is optional; the quotes are required.)

Quotation marks may not be used within a string. However, the closing quotation can be omitted if it is the last character on a logical line. (See Section 7

STRINGS).

Variable: A variable is the name for a numerical or other quantity which may

(or may not) change. Variable names may be up to 120 characters long.

However, a variable name must start with an alphabetic letter, and may contain only capital letters and numerical digits. lt is advisable not to use a keyword as a variable name or as the first part of a variable name as it may not be interpreted correctly. Examples of storing a value in a variable:

LETC127003=1_234

LETUARIABLE112=257.543

LETA=1

LETF5TH-G.5

LETTHISNO = 59.309

Note:

LET is optional and may be omitted)

Variable Name Limit:

ATARI BASIC limits the user to 128 variable names.To bypass this problem, use individual elements of an array instead of having separate variable names.

BASIC keeps all references to a variable which has been deleted from a program, and the name still remains in the variable name table.

If the screen displays an ERROR-4 (Too Many Variables) message, use the following procedure to make room for new variable names:

LIST filesPec

NEW

ENTER filesPec

The LIST filespec writes the untokenized version of the program onto a disk or cassette. NEW clears the program and the table areas. The program is then reentered, re-tokenized, and a new variable table is built. (The tokenized version is Atari BASIC's internal format. The untokenized versions in ATASCH which is the version displayed on the screen).

Arrays and Array Variables: An array is a list of places where data can be

Med for future use. Each of these places is called an element, and the whole array or any element is an array variable. For example, define "Array A" as having 6 elements. These elements are referred to by the use of subscripted variables such as A(2), A(3), A(4), etc. A number can be stored in each element. This may be accomplished element by element (using the LET statement), or as a part of a FOR/NEXT loop (see Chapter 8).

Note:

Never leave blanks between the element number in parentheses and the name of the array.

Correct Incorrect

A(23)

ARRAY(3)

X123(38)

(23)

ARRAY (3)

X123

(38)

SPECIAL

NOTATIONS

USED

IN THIS

MANUAL

Line Format:

The format of a line in a BASIC program includes a line number

(abbreviated to lineno) at the beginning of the line, followed by a statement keyword, followed by the body of the statement and ending with a line terminator command ( nETuRN key). In an actual program, the four elements might look like this:

Line Number

100

STATEMENT

Keyword

PRINT

Body

A/X * (Z + 4.567)

Terminator

RETURN

Several statements can be typed on the same line provided they are separated by colons (:). See IF/THEN in Section 5, and Section 11.

Capital Letters: In this book, denote keyvvords to be typed by the user in upper case form exactly as they are printed in this text. Reverse-video characters will not work except in the case of the RUN command. Here are a few examples:

PRINT INPUT LIST END GOTO GOSUB FOR NEXT IF

Lower Case Letters: In this manual, lower case letters are used to denote the various classes of items which may be used in a program, such as variables

(var), expressions (exp), and the like. The abbreviations used for these classes of items are shown in Table 1.1.

General Information

Items in Brackets: Brackets, II 1, contain optional items which may be used, but are not required. If the item enclosed in brackets is followed by three dots

[exp,...], it means that

any

number of expressions may be entered, but none are required.

Items stacked vertically in braces: Items stacked vertically in braces indicate that any one of the stacked items may be used, but that only one at a time is permissible. In the example below, type either the GOTO or the GOSUB.

wo{

GOTO 12000

GOSUB

Command abbreviations in headings: If a command or statement has an abbreviation associated with it, the abbreviation is placed following the full name of the command in the heading; e.g., LET (L.).

ABBREVIATIONS

The following table explains the abbreviations used throughout this manual:

USED IN THIS

MANUAL

TABLE 1.1 ABBREVIATIONS

avar

Arithmetic Variable: A location where a numeric value is stored. Variable names may be from 1 to 120 alphanumeric characters, but must start with an alphabetic character, and all alpha characters must be unreversed and upper case.

svar

String Variable: A location where a string of characters may be stored. The same name rules as avar apply, except that the last character in the variable name must be a $. String variables may be subscripted. See Section 7, STRINGS.

mvar var aop

Matrix Variable: Also called a

Subscripted Variable.

An element of an array or matrix. The variable name for the array or matrix as a whole may be any legal variable name such as A, X,

Y, ZIP, or K. The subscripted variable (name for the particular element) starts with the matrix variable, and then uses a number, variable, or expression in parentheses

immediately

following the array or matrix variable. For example, A(ROW), A(1), A(X + 1).

Variable: Any variable. May be mvar, avar, or svar.

Arithmetic Operator. lop aexp lexp

Logical operator.

Arithmetic Expression: Generally composed of a variable, function, constant, or two arithmetic expressions separated by an arithmetic ourator.

Logical Expression: Generally composed of two arithmetic or string expressions separated by a logical operator. Such an expression evaluates to either a 1 (logical true) or a 0 (logical false).

For example, the expression 1<2 evaluates to the value 1 (true) while the expression "LEMON" = "ORANGE" evaluates to a zero

(false) as the two strings are not equal.

4 General Information

OPERATING

MODES

SPECIAL

FUNCTION

KEYS

sexp exp lineno adata filespec

String Expression:

Can consist of a string variable, string literal

(constant), or a function that returns a string value.

Any expression, whether sexp or aexp.

Line Number:

A constant that identifies a particular program line in a deferred mode BASIC program. Must be any integer from 0 through 32767. Line numbering determines the order of program execution.

ATASCII Data:

Any ATASCII character excluding commas and carriage returns. (See Appendix C.)

File Specification:

A string expression that refers to a device such as the keyboard or to a disk file. lt contains information on the type of I/O device, its number, a colon, an optional file name, and an optional filename extender. (See OPEN, Section 5.)

Example filespec: "Dl:NATALIE.ED"

Direct Mode:

Uses no line numbers and executes instruction immediately after

RETURN

key is pressed.

Deferred Mode:

Uses line numbers and delays execution of instruction(s) until the RUN command is entered.

Execute Mode:

Sometimes called Run mode. After RUN command is entered, each program line is processed and executed.

Memo Pad Mode:

A non-programmable mode that allows the user to experiment with the keyboard or to leave messages on the screen.

Nothing written while in Memo Pad mode affects the RAM-resident program.

CAPS/LOWR

1113

Reverse (Inverse) Video key,

or "ATARI LOGO KEY". Press- ing this key causes the text to be reversed on the screen (dark text on light background). Press key a second time to return to normal text.

Lower Case key:

Pressing this key shifts the screen characters from upper case (capitals) to lower case. To restore the characters to upper case, press the

sHIFT

key and the

CAPS/LOWR

key simultaneously.

Escape key:

Pressing this key causes a command to be entered into a program for later execution.

Example: To clear the screen, you would enter:

10 PRINT "

Em3

CLEAR "

and press

RETURN .

Escape is also used in conjunction with other keys to print special graphic control characters. See Appendix F and back cover for the specific keys and their screen-character representations.

General Information

BREAK

SYSTEM RESET

SET-CLR-TAB

Break key: Pressing this key during program execution causes execution to stop. Execution may be resumed by typing CONT followed by pressing

RETURN

System Reset key: Similar to

BREAK

in that pressing this key stops program execution. Also returns the screen display to

Graphics mode 0, clears the screen, and returns margins and other variables to their default values.

Tab key: Press

SHIFT

and the

SET-CLR-TAB

keys simultaneously to set a tab. To clear a tab, press the

EZ3

and

SET•CLR•TAB

keys simultaneously. Used alone, the

SET-CLR-TAB

advances the cursor to the next tab position. In Deferred mode, set and clear tabs by preceding the above with a line number, the command PRINT, a quotation mark, and press the

EZ

key.

INSERT

DELETE BACK S

CLEAR

RETURN

Examples:

100 PRINT

200

CE31

SHIFT SET-CLR-TAB

1E3 Ez3

SET•CLR-TAB

Default tab settings are placed at columns 7, 15, 23, 31, and 39.

Insert key: Press the

SHIFT

and

INSERT

keys simultaneously to insert a line. To insert a single character, press the

GE3

and

INSERT

keys simultaneously.

Delete key: Press the

SHIFT

and

DELETE

keys simultaneously to delete a line. To delete a single character, press

EM

and

DELETE

simultaneously.

Back Space key: Pressing this key replaces the character to the left of the cursor with a space and moves cursor back one space.

Clear key: Pressing this key while holding down the

sHIFT or

EM

key blanks the screen and puts the cursor in the upper left corner.

Return key: Terminator to indicate and end of a line of BASIC.

Pressing this key causes a numbered line to be interpreted and added to a BASIC program RAM. An unnumbered line (in Direct mode) is interpreted and executed immediately. Any variables are placed in a variable table.

ARITHMETIC

OPERATORS

The Atari Personal Computer System uses five arithmetic operators:

+ addition (also unary plus; e.g., +5)

- subtraction (also unary minus; e.g., - 5)

* multiplication

/ division

A

exponentiation

LOGICAL

OPERATORS

The logical operators consists of two types:

Operator is NOT. The binary operators are:

unary

and

binary.

The unary

General Information

AND

Logical AND

Logical OR

Examples:

10 IF A=12 ANO T=0 THEN PRINT "GOOD"

10 A = (C)1) AND (N<1)

10 A = (C+1) OR (N-1)

Both expressions must be true before GOOD is printed.

If both expressions true, A = +1; otherwise

A = 0.

If eit her expression true, A= +1; otherwise

A=0.

If expression is false,

A= + I; otherwise A =0.

10

A = NOT( C+1

The rest of the binary operators are relational.

< The first expression is less than the second expression.

> The first expression is greater than the second.

.= The expressions are equal to each other.

< = The first expression is less than or equal to the second.

> = The first expression is greater than or equal to the second.

< > The two expressions are not eclual to each other.

These operators are most frequently used in IF/THEN statements and logical arithmetic.

OPERATOR

PRECEDENCE

Operations within the innermost set of parentheses are performed first and pro- ceed out to the next level. When sets of parentheses are enclosed in another set, they are said to be "nested". Operations on the same nesting level are performed in the following order:

Highest < , > , =,< =, >=,<-> Relatibnal operators used in string expresprecedence sions. Have same precedence and are performed from left to right.

Unary minus

Exponentiation.

Multiplication and division have the same precedence level and are performed from left

+, — to right.

Addition and subtraction have the same precedence level and are performed from left to right.

Lowest

< , > , = =, >=,< > Relational operations in numeric expressions have the same precedence level from left to

NOT right.

Unary Operator

AND

Logical AND

Logical OR precedence

General Information 7

BUILT-IN

FUNCTIONS

GRAPHICS

The section titled

FUNCTION LIBRARY

explains the arithmetic and special functions incorporated into Atari BASIC.

Atari graphics include 9 graphics modes. The commands have been designed to allow- maximum flexibility in color choice and pattern variety. Section 9 explains each command and gives examples of the many ways to use each.

SOUND AND

GAMES

CONTROLLERS

The Atari Personal Computer is capable of emitting a large variety of sounds including simulated explosions, electronic music, and "raspberries." Section 10 defines the commands for using the SOUND function and for controlling paddie, joystick, and keyboard controllers.

WRAPAROUND

The ATARI Personal Computer System has screen wraparound thus allowing

AND KEYBOARD greater flexibility. lt also allows the user to type one key ahead. If the user presses and holds any key, it will begin repeating after 1/2 second.

ROLLOVER

ERROR

MESSAGES

If a data entry error is made, the screen display shows the line reprinted preceded by the message ERROR- and the offending character is highlighted. After correcting the character in the original line, delete the line containing the

ERROR

before pressing

RETURN

Appendix B contains a list of all the error messages and their definitions.

General Information

2 COMMANDS

BYE (B.)

CONT (CON.)

END

Whenever the cursor (0) is displayed on the screen, the computer is ready to accept input. Type the command (in either Direct or Deferred mode), and press

RETURN

This section describes the commands used to clear computer memory and other useful control commands..

The commands explained in this section are the following:

BYE

CONT

END

LET

LIST

NEW

REM

RUN

STOP

Format:

BYE

Example:

BYE

The current function of the BYE command is to exit BASIC and put the computer in Memo Pad mode. This allows the user to experiment with the keyboard or to leave messages on the screen without disturbing any BASIC program in memory. To return to BASIC, press

SYSTEM RESET .

Format:

CONT

Example:

CONT

Typing this command followed by a

RETURN

causes program execution to resume. If a

BREAK

, STOP, or END is encountered, the program will stop until

CONT

RETURN

is entered. Execution resumes at the next sequential

line number

following the statement at which the program stopped.

Note: If the statement at which the program is halted has other commands on the same numbered line which were not executed at the time of the

BREAK

STOP, or END, they will

not

be executed. On CONT, execution resumes at the next numbered line. A loop may be incorrectly executed if the program is halted before the loop completes execution.

This command has no effect in a Deferred mode program.

Format:

END

Example:

1000 END

This command terminates program execution and is used in Deferred mode. In

Atari BASIC, an END is not required at the end of a program'. When the end of the program is reached, Atari BASIC automatically closes all flies and turns off sounds (if any). END may also be used in Direct mode to close flies and turn off sounds.

Commands 9

LET

(LE.)

LAYF

NEW

REM

(R. or

. SPACE )

Format:

1E1'1 var = exp

Example:

LET X = 3.142 * 16

LET X = 2

This statement is optional in defining variables. lt can just as easily be left out of the statement. lt may be used, however, to set a variable name eclual to a value.

Format:

LIST [lineno [ , lineno]

LIST [filespec [ ,lineno [ ,lineno]1 ]

Examples:

LIST

LIST 10

LIST,10,100

LIST "P.",20,100

LIST "P"

LIST "D.DEMO.LST"

This command causes the computer to display the source version of all lines currently in memory if the command is entered without line number(s), or to display a specified line or lines. For example, LIST 10,100

RETURN

displays lines

10 through 100 on the screen. If the user has not typed the lines into the computer in numerical order, a LIST will automatically place them in order.

Typing L."P will print the RAM-resident program on the printer.

LIST can be used in Deferred mode as part of an error trapping routine (See

TRAP in Section 4).

The LIST command is also used in recording programs on cassette tape. The second format is used and a filespec is entered. (See Section 5 for more details on peripheral devices.) If the entire program is to be listed on tape, no line numbers need be specified.

Example:

LIST "Cl"

1000 LIST "Cl"

Format:

NEW

Example: NEW

This command erases the program stored in RAM. Therefore, before typing

NEW, either SAVE or CSAVE any programs to be recovered and used later.

NEW clears BASIC's internal symbol table so that no arrays (See Section 8) or strings (See Section 7) are defined. Used in Direct mode.

Format:

REM text

Example:

10 REM ROUTINE TO CALCULATE X

This command and the text following it are for the user's information only. lt is ignored by the computer. However, it is included in a LIST along with the other numbered lines. Any statement on the same numbered line which occurs after a

REM statement will be ignored.

10 Commancls

RUN (RU.)

STOP (STO.)

Format:

Examples:

RUN Efilesped

RUN

RUN "D:MENU"

This command causes the computer to begin executing a program. If no filespec is specified, the current RAM-resident program begins execution. If a filespec is included, the computer retrieves the specified, tokenized program from the specified file and executes it.

All variables are set to zero and all open flies and peripherals are closed. All arrays, strings, and matrices are eliminated and all sounds are turned off. Unless the TRAP command is used, an error message is displayed if any error is detected during execution and the program halts.

RUN can be used in Deferred mode.

Examples:

19 PRINT "QUER Ale OVER AGAIN. "

29 Rill

Type RUN and press

RETURN

To end, press

BREAK

To begin program execution at a point other than the first line number, type

GOTO

followed by the specific line number, then press

RETURN

Format:

Example:

STOP

100 STOP

When the STOP command is executed in a program, BASIC displays the message

STOPPED AT LINE ,

terminates program execution, and returns to Direct mode. The

STOP

command does not close files or turn off sounds, so the program can be resumed by typing CONT

RETURN .

Conunmuts

NOTES

Notes

SCREEN

EDITING

3 EDIT

FEATURES

In addition to the special function keys described in Section 1, there are cursor control keys that allow immediate editing capabilities. These keys are used in conjunction with the

SHIFT or

Ez3

keys.

The following key functions are described in this section:

EMD

SHIFT

CTRL

1321 o

Eia o

EiG3

•

INSERT

113131

DELETE

INSERT

SHIFT

SHIFT DELETE

CAPS/LOWR

SHIFT

cm. 2

CTRL

BREAK

The keyboard and display are logically combined for a mode of Operation known as screen editing. Each time a change is completed on the screen, the

RETURN key must be pressed. Otherwise, the change is not made to the program in RAM.

Example: 10

RE.M PRESS F:E.TUR±,- 1„zh,FT ER L I NE 7--.0 I T

TM7

•

.PiZTHT

32 PRINT "THIS IS

TU:

'T"p17 ,

- • •

To delete line 20 from the program, type the line number and press the

RETURN key. Merely deleting the line from the screen display does not delete it from the program.

The screen and keyboard as devices are described in Section 5.

13113

Control key. Striking this key in conjunction with the arrow keys produces the cursor control functions that allow the user to move the cursor anywhere on the screen without changing any characters already on the screen. Other key combinations control the setting arid clearing of tabs, halting and restarting program lists, and the graphics control symbols.

Striking a key while holding the

Ez3

key will produce the upper-left symbol on those keys having three functions.

SHWT

Shift key: This key is used in conjunction with the numeric keys to display the symbols shown on the upper half of those keys. lt is also used in conjunction

Edit Features

DOUBLE-KEY

FUNCTIONS with other keys to insert and delete lines, return to a normal, upper case letter display, and to display the function symbols above the subtraction, equals, addition, and multiplication operators as well as the brackets, [ ]‚ and question mark,?.

Cursor Control Keys

12E3 o

EID 1D

GED o

Moves cursor up one physical line without changing the program or display.

Moves cursor one space to the right without disturbing the program or display.

Moves cursor down one physical line without changing the program or display.

▪

c:

Moves cursor one space to the left without disturbing the program or display.

Like the other keys on the Atari keyboard, holding the cursor control keys for more than 1/2 second causes the keys to repeat.

Keys Used With

En

Ez3

INSERT

Inserts one character space.

CTRL

DELETE

CTRL

EM

Can

Deletes one character or space.

Stops temporarily and restarts screen display without "breaking out" of the program.

Rings buzzer.

Indicates end-of-file.

SHIFT

SHIFT DELETE

SHIFT

BREAK

Ca

INSERT

CAPS/LOWR

Keys Used With

SHIFT

Inserts one physical line.

Deletes one physical line.

Returns screen display to upper-case alphabetic characters.

Special Function Keys

Stops program execution or program list, prints a

READY on the screen, and displays cursor.

Allows commands normally used in Direct mode to be placed in Deferred mode; e.g., In Direct mode, cnu

CLEAR clears the screen display. To clear the screen in Deferred mode, type the following after the program line number. Press

ESC then press c-rTit. and

CLEAR together.

PRINT "

ESC

(E3

CLEAR "

Edit Features

4 PROGRAM

STATEMENTS

This section explains the commands associated with loops, conditional and unconditional branches, error traps, and subroutines and their retrieval. lt also explains the means of accessing data and the optional command used for defining variables.

The following commands are described in this section:

FOR, TO, STEP/NEXT IF/THEN

GOSUB/RETURN ON, GOSUB

GOTO ON, GOTO

POP

RESTORE

TRAP

FOR (F.), TO,

STEP/NEXT

(N.)

Format:

FOR avar = aexpl TO aexp2 [STEP aexp3]

NEXT avar

Examples: FOR X = 1 TO 10

NEXT X

FOR Y = 10 TO 20 STEP 2

NEXT Y

FOR INDEX = Z TO 100 * Z

NEXT INDEX

This command sets up a loop and determines how many times the loop is executed. The loop variable (avar) is initialized to the value of aexpl. Each time the

NEXT avar statement is encountered, the loop variable is incremented by the aexp3 in the STEP statement. The aexp3 can be positive or negative integers, decimals, or fractional numbers. If there is no STEP aexp3 command, the loop increments by one. When the loop completes the limit as defined by aexp2, it stops and the program proceeds to the statement immediately following the

NEXT statement; it may be on the same line or on the next sequential line.

Loops can be nested, one within another. In this case, the innermost loop is completed before returning to the outer loop. The following example illustrates a nested loop program.

10 FÜR X=1 TO 3

20 PRINT "OUTER LOOP"

30 Z=0

40 Z=Z+2

50 FÜR Y=1 TO 9 STrP

7

GO PRINT "

INNER !OOP"

70 NEXT Y

80 NEXT X

EN°

Figure 4-1. Nested Loop Program

Program Statements

In Figure 4-1, the outer loop will complete three passes ( X =

1 to 3 ). However, before this first loop reaches its NEXT X statement, the program gives control to the inner loop. Note that the NEXT statement for the inner loop must precede the NEXT statement for the outer loop. In the example, the inner loop's number of passes is determined by the STEP statement

(STEP Z).

In this case,

has been defined as 0, then redefined as

Z + 2.

Using this data, the computer must complete three passes through the inner loop before returning to the outer loop.

The aexp3 in the step statement could also have been defined as the numerical value 2.

The program run is illustrated in Figure 4-2.

OUTER LOOP

INNER LOOP

IHNER LOOP

OUTER LOOP

INNER LOOP

OUTER LOOP

INNER LOOP

Figure 4-2. Nested Loop Execution

The return address for the loops are placed in a special group of memory addresses referred to as a stack. The information is "pushed" on the stack and when used, the information is "popped" off the stack (see

POP.)

GOSUB (GOS.)

RETURN (RET.)

Format:

GOSUB lineno lineno

RETURN

Example:

100 GOSUB 2000

2000 PRINT "SUBROUTINE"

2010 RETURN

A subroutine* is a program or routine used to cornpute a certain value, etc. lt is generally used when an Operation must be replaced several times within a program secluence using the same or different values. This command allows the user to "call" the subroutinel, if necessary. The last line of the subroutine must contain a RETURN statement. The RETURN statement goes back to the physical line following the GOSUB statement.

Like the preceding

FOR/NEXT

command, the

GOSUB/RETURN

command uses a stack for its return address. If the subroutine is not allowed to complete normally; e.g., a GOTO lineno before a RETURN, the GOSUB address must be

"popped" off the stack (see

POP)

or it could cause future errors.

* Generally, a subroutine can do anything that can be done in a program. lt is used to save memory and program-entering time, and to make programs easier to read and debug.

Program Statements

GOTO (G.)

To prevent accidental triggering of a subroutine (which normally follows the main program), place an

END

statement preceding the subroutine. The following program demonstrates the use of subroutines.

10 PRINT ")"

20 REM EXAmPLE LEE OF GOSUE/RETURN

30 •=122

4n GOSUP 120n

50 X=I20

60 GOSUB 1000

70 x=50

30 GOSUE 100n

90 END lenn

1010 ‘,..Z=x+'.1"

1020 PRINT

1222 RETURN

X,7

(Clear screen)

Figure 4

3. GOSUB/RETURN Program Listing

In the above program, the subroutine, beginning at line 1000, is called three times to compute and print out different values of X and Y. Figure 4-4 illustrates the results of executing this program.

400

480

200

300

360

150

Figure 4-4. GOSUB/RETURN Program Run

Format: {

GO TO I aexp

GOTO

Examples:

100 GOTO 50

500 GOTO (x+ Y)

The GOTO command is an unconditional branch statement just like the GOSUB command. They both immediately transfer program control to a target line number or arbitrary expression. However, using anything other than a constant will make renumbering the program difficult. If the target line number is non-existent, an error results. Any GOTO statement that branches to a preceding line may result in an "endless" loop. Statements following a GOTO statement will not be executed. Note that a conditional branching statement (See

IF/THEN)can

be used to break out of a GOTO loop. The following program illustrates two uses of the GOTO command.

Program Statements 17

10 PRINT

20 PRINT :PRINT "ONE"

30 PRINT "TWO"

40 PRINT "THREE"

50 PRINT "FOUR"

60 PRINT "FIIJE"

65 GOTO 100

70 PRINT

80 PRINT

90 PRINT _.,..„.18383111

END

100 PRINT "SIX"

110 PRINT "SEUEN"

120 PRINT uEIGHTH

172

PRINT "NINE"

140 PRINT 4 TEN"

150 GOTO 70

Figure 4-5. GOTO Pro gram Listing

Upon execution, the numbers in the above listing will be listed first followed by the three rows of symbols. The symbols listed on lines 70, 80, and 90 are ignored temporarily while the program executes the GOTO 100 command. lt proceeds with the printing of the numbers "SIX" through "TEN", then executes the second GOTO statement which transfers program control back to line 70. (This is just an example. This program could be rewritten so that no GOTO statements were used.) The program, when executed, looks like the following:

ONE

TWO

THREE

FOUR

FIUE

SEUEN .

EIGHT

NINE

TEN

IF/THEN

Program Statements

Figure 4

6. GOTO Program Run

Format:

IF aex] ) THEN { lineno

Examples: IF X = statement [:statement...]

100 THEN 150

A$ = "ATARI" THEN 200

IF AA

IF X =

= 145 and BB = 1 THEN PRINT AA, BB

100 THEN X = 0

The IF/THEN statement is a conditional branch statement. This type of branch occurs only if certain conditions are met. These conditions may be either arithmetical or logical. If the aexp following the IF statement is true (non-zero), the program executes the THEN part of the statement. If, however, the aexp is false (a logical 0), the rest of the statement is ignored and program control passes to the next numbered line.

In the format, IF aexp THEN lineno, lineno must be a constant, not an expression and specifies the line number to go to if the expression is true. If several statements occur after the THEN, separated by colons, then they will be executed if and only if the expression is true. Several IF statements may be nested on the same line. For example:

122 IF X=5 THEN IF Y=7 THEN R=9:GOT0200

The statements R=9: GOTO 100 will be executed only if X=5 and Y =3. The statement Y=3 will be executed if X= 5.

The following program demonstrates the IF/THEN statement.

5 .GRAPHICS 0:? :? "

10 ? "ENTER A";INPUT A

IF DEMO"

20 IF,A=1 THEN eREM MULTIPLE STATEMENT

S HERE WILL NEUER BE EXECUTEDM

30 ? :? "A 13 NOT 1. EXECUTION CONTINUE

HEFE WHEN THE EXPRESSION IG FALSE."

40 IF•A=1 THEN ? :? "A=1":? "YES, IT IS

REALLY 1..":REM MULTIPLE STATEMENTS HEFE

WILL BE EXECUTED ONLY IF A=1!!

50 ? '? "EXECUTION CONTINUES HEFE IF A<>

1 OR AFTER 'YES, IT IS REALLY 1' IS DISP

LAYED."

AO GOTO 10

Figure 4-7. IF/THEN Program

ENTER A

A IS NOT 1. EXECUT ION CONTINUES HERE WH

EN THE EXPRESSION IS FALSE.

EXECUTION CONTINUES HERE IF A(>1 OR AFTE

R 'YES, IT IS REALLY 1 IS DISPLAYED.

ENTER A

(entered 2)

(entered 1)

A=1

YES, IT REALLY 1.

EXECUTION CONTIMES HERE IF A<>1 OR AFTE

R 'YES, IT IS REALLY 1' IS DISPLAYED.

ENTER A

Figure 4-8. IF/THEN Program Execution.

Program Statements 19

ON/GOSUB/

RETURN

ON/GOTO

POP

Program Statements

Format:

ON aexp GOTOI lineno [ ,lineno...]

GOSUB

Examples:

100 ON X GOTO 200, 300, 400

100 ON A GOSUB 1000, 2000

100 ON SQR(X) GOTO 30, 10, 100

Note:

GOSUB

and

GOTO

may not be abbreviated.

These two staternents are also conditional branch statements like the IF/THEN statement. However, these two are more powerful. The aexp must evaluate to a positive number which is then rounded to the nearest positive integer (whole number) value up to 255. If the resulting number is 1, then program control passes to the first lineno in the list following the GOSUB or GOTO. If the resulting number is 2, program control passes to the second lineno in the list, and so on. If the resulting number is 0 or is greater than the number of linenos in the list, the conditions are not met and program control passes to the next statement which may or may not be located on the same line. With ON/GOSUB, the selected subroutine is executed and then control passes to the next statement.

The following routine demonstrates the ON/GOTO statement:

10 X=X+1

20 ON X GOTO 100,200,300,400,500

30 IF X>5 THEN PRINT "COMPLETE.".END

40 GOTO 10

50 ENO

109 PRINT uNOW WORKING AT LINE 100".GOTO

200 PRINT "NDW WORKING AT LINE 200".GOTO

300 PRINT "NOW WORKING AT LINE 300".G0T0

400 PRINT uNOW WORKING AT LINE 400".GOTO

500 PRINT uNOW WORKING AT LINE 500".GOTO

Figure 4-9 ON/GOTO Program Listing

When the program is executed, it looks like the following:

NOW WORKING AT LINE 100

NOW WORKING AT LINE 200

NOW WORKING AT LINE 300

NOW WORKING AT LINE 400

NOW WORKING AT LINE 500

WIPLETE

Figure 4-10 ON/GOTO Program Execution

Format:

POP

Example:

1000 POP

In the description of the FOR/NEXT statement, the

stack

was defined as a group of memory addresses reserved for return addresses. 'The top entry in the stack controls the number of loops to be executed and the RETURN target line for a

GOSUB. If a subroutine is not terminated by a RETURN statement, the top memory location of the stack is still loaded with some numbers. If another

GOSUB is executed, that top location needs to be cleared. To prepare the stack for a new GOSUB, use a POP to clear the data from the top location in the stack.

The POP command must be used according to the following rules:

lt must be in the execution path of the program.

lt must follow the execution of any GOSUB statement that is not brought back to the main program by a RETURN statement.

The following example demonstrates the use of the POP command with a

GOSUB when the RETURN is not executed:

10 GOSUB 1000

15 REM LINE 20 WILL NOT BE EXECUTED

20 PRINT "NORMAL RETURN PRINTS THIS MESS

AGE "

30 PRINT "ABNORMAL RETURN PRINTS THIR NE

SSAGE."

4n POP

999 ENO

1002 PRINT "NOW

7-XECUTING SUBROUTINE."

1012 GOTO 30

1222 RETURN

Figure 4-11. GOSUB Statement With POP

RESTORE

(RES.) Format:

RESTORE [aexp]

Example:

100 RESTORE

The Atari Personal Computer System contains an internal "pointer" that keeps track of the DATA statement item to be read next. Used without the optional aexp, the RESTORE statement resets that pointer to the first DATA item in the program. Used with the optional aexp, the RESTORE statement sets the pointer to the first DATA item on the line specifed by the value of the aexp. This statement permits repetitive use of the same data.

10 FOR N=1

20 RE:43

72 RgSinR

RED

50 M=A+B

GO PRINT "TO-U;i! Eh;

70 WNT N

20 ,uND

90 DAT 72, 5

Figure 4-12. Restore Program Listing

On the first pass through the loop, A will be 30 and B will be 30 so the total line

50 will print SUM TOTAL EQUALS 60, but on the second pass, A will equal 15

PrOgranl Statements

TRAP (T.) and B, because of the RESTORE statement, will still equal 30.

PRINT statement

Therefore, the in line 50 will display

SUM TOTAL EQUALS 45.

Format:

TRAP aexp

Example:

100 TRAP 120

The TRAP statement is used to direct the program to a specified line number if an error is detected. Without a TRAP statement, the program stops executing when an error is encountered and displays an error message on the screen.

The TRAP statement works on any error that may occur after it has been executed, but once an error has been detected and trapped, it is necessary to reset the trap with another TRAP command. This TRAP command may be placed at the beginning of the section of code that handles input from the keyboard so that the TRAP is reset after each error. PEEK(195) will give you an error message (see Appendix B). 256*PEEK(187)+ PEEK(186) will give you the number of the line where the error occurred. The TRAP may be cleared by executing a

TRAP statement with an aexp whose value is from 32767 to 65535 (e.g., 40000).

PrOgra/72 Statements

5 INPUT/OUTPUT

COMMANDS AND DEVICES

This section describes the input/output devices and how data is moved between them. The commands explained in this section are those that allow access to the input/output devices. The input commands are those associated with getting data into the RAM and the devices geared for accepting input. The output commands are those associated with retrieving data from RAM and the devices geared for generating output.

The commands described in this section are:

CLOAD

CSAVE

DOS

ENTER

INPUT

LOAD

LPRINT

NOTE

OPEN/CLOSE

POINT

PRINT

PUT/GET

READ/DATA

SAVE

STATUS

XIO

INPUT/OUTPUT

DEVICES

The hardware configuration of each of the following devices is illustrated in the individual manuals furnished with each. The Central Input/Output (GI) subsystem provides the user with a single interface to access all of the System peripheral devices in a (largely) independent manner. This means there is a single entry point and a device-independent calling sequence. Each device has a symbolic device name used to identify it; e.g., K: for the keyboard. Each device must be opened before access and each must be assigned to an Input/Output Control Block (IOCB). From then on, the device is referred to by its IOCB number.

ATARI BASIC contains 8 blocks in RAM which identifies to the Operating

System the information it needs to perform an I/O operation. This information includes the command, buffer length, buffer address, and two auxiliary control variables. ATARI BASIC sets up the IOCB's, but the user must specify which

IOCB to use. BASIC reserves IOCB

110 for I/O to the Screen Editor, therefore the user may not request IOCB #0. The GRAPHICS statement (see Section 9) opens

IOCB 116 for input and output to the screen. (This is the graphics window S:).

IOCB

117 is used by BASIC for the LPRINT, CLOAD, and CSAVE commands. The

IOCB number may also be referred to as the device (or file) number. IOCB's 1 through 5 are used in opening the other devices for input/output operations. If

I0C13

117

is in use, it will prevent LPRINT or some of the other BASIC I/O statements from being performed.

Keyboard: (K:) Input only device. The keyboard allows the user to read the converted (ATASCII) keyboard data as each key is pressed.

Line Printer: (P:) Output only device. The line printer prints ATASCII characters, a line at a time. lt recognizes no control characters.

Program Recorder: (C:) Input and Output device. The recorder is a read/write device which can be used as either, but never as both simultaneously. The cassette has two tracks for sound and program recording purposes. The audio track cannot be recorded from the ATARI system, but may be played back through the television speaker.

COMMCIMIS and

Devices

Disk Drives: (D1:, D2:, D3:, D4:)

Input and Output devices. If 16K of RAM is installed, the ATARI can use from one to four disk drives. If only one disk drive is attached, there is no need to add a number after the symbolic device code D.

Screen Editor: (E:)

Input and Output device. This device uses the keyboard and display (see

TV Monitor)

to simulate a screen editing terminal. Writing to this device causes data to appear on the display starting at the current cursor position. Reading from this device activates the screen editing process and allows the user to enter and edit data. Whenever the

RETURN key

is pressed, the entire logical line within which the cursor resides is selected as the current record to be transferred by CIO to the user program. (See Section 9).

TV Monitor: (S:)

Input and Output device. This device allows the user to read characters from and write characters to the display, using the cursor as the screen addressing mechanism. Both text and graphics operations are supported.

See Section 9 for a complete description of the graphics modes.

Interface, RS

232: (R:)

The RS-232 device enables the ATARI System to interface with RS-232-compatible devices such as printers, terminals, and plotters. lt contains a parallel port to which the 80-column printer (ATARI

825TM) can be attached.

CLOAD (CLOA.)

Format:

CLOAD

Examples:

CLOAD

100 CLOAD

This command can be used in either Direct or Deferred mode to load a program from cassette tape into RAM for execution. On entering CLOAD, one bell rings to indicate that the PLAY button needs to be pressed followed by

RETURN

However, do not press PLAY until after the tape has been positioned. Specific instructions for CLOADing a program are contained in the

ATARI 410 Progranz

Recorder Manual.

Steps for loading oversized programs are included in the paragraphs under

CHAINING PROGRAMS

at the end of this section.

CSAVE (CS.)

Format:

CSAVE

Examples:

CSAVE

100 CSAVE

100 CS.

This command is usually used in Direct mode to save a RAM-resident program onto cassette tape. CSAVE saves the tokenized version of the program. On entering CSAVE two bells ring to indicate that the PLAY and RECORD buttons must be pressed followed by

RETURN

Do not, however, press these buttons until the tape has been positioned. lt is faster to save a program using this command rather than a SAVE "C" (see SAVE) because short inter-record gaps are used.

Notes:

Tapes saved using the two commands, SAVE and CSAVE, are not compatible lt may be necessary to enter an LPRINT (see

LPRINT)

before using

CSAVE. Otherwise, CSAVE may not work properly.

For specific instructions on how to connect and operate the hardware, cue the tape, etc., see the

ATARI 410 Program Recorder Manual.

1/0 Garnnlands and Devices

DOS (DO.)

ENTER (E.)

INPUT (I.)

Format:

Example:

DOS

The DOS command is used to go from BASIC to the Disk Operating System

(DOS). If the Disk Operating System has not been booted into memory, the computer will go into Memo Pad mode and the user must press

SYSTEM RESET to return to Direct mode. If the Disk Operating System has been booted, the DOS Menu is displayed. To clear the DOS Menu from the screen, press

SYSTEM RESET .

Control then passes to BASIC. Control can also be returned to BASIC by selecting

(Run

Cartridge) on the DOS Menu.

The DOS command is usually used in Direct mode; however, it may be used in a program. For more details on this, see the

Atari DOS Manual.

Format:

ENTER filespec

Examples:

ENTER "C

ENTER "D:DEMOPR.INS"

This statement causes a cassette tape to play back a program originally recorded using LIST (see Section 2,

LIST).

The program is entered in unprocessed (untokenized) form, and is interpreted as the data is received. When the loading is complete, it may be run in the normal way. The ENTER command may also be used with the disk drive. Note that both LOAD and CLOAD (see Section 2) clear the old program from memory before loading the new one. ENTER merges the old and new programs. This ENTER statement is usually used in Direct mode.

Format:

Examples:

avar I [ avar svar

, svar •••

100 INPUT X

100 INPUT N$

100 PRINT "ENTER THE VALUE OF X"

110 INPUT X

This statement requests keyboard data from the user. In execution, the computer displays a ? prompt when the program encounters an INPUT statement. lt is usually preceded by a PRINT statement that prompts the user as to the type of information being requested.

String variables are allowed only if they are not subscripted. Matrix variables are not allowed.

The itaexp is optional and is used to specify the file or device number from which the data is to be input (see Input/Output Devices). If no traexp is specified, then input is from the screen editor

(E:).

If several strings are to be input from the screen editor, type one string, press

RETURN

type the next string,

RETURN

etc. Arithmetic numbers can be typed on the same line separated by commas.

19 PRINT "ENTER 5 MUMBERS TO BE SUMMET'

20 FÜR N=1 TO 5

30 INPUT X

40 C=C+X

50 NEXT M

60 PRINT "THE SUM OF YOUR NUMBERS IS n; C;

70 EMO

Figure 5-1 Input Program Listing

I/O Conzmands and Devices

LOAD (LO.)

Format:

LOAD filespec

Example: LOAD "D1:JANINE.BRY"

This command is similar to CLOAD except the full file name system can be used.

LOAD uses long inter-record gaps on the tape (see CLOAD) and uses the tokenized version of the program. When using only one disk drive, it is not necessary to specify a number after the "D" because the default is disk drive #1.

LPRINT (LP.)

Format:

LPRINT [exp][ ; exp..

Example: LPRINT "PROGRAM TO CALCULATE X"

100 LPRINT X;" ";Y;" ";Z

This statement causes the computer to print data on the line printer rather than

on the screen. lt can be used in either Direct or Deferred modes. lt requires no device specifier and no OPEN or CLOSE statement. (BASIC uses IOCB #7.)

The

above program listing illustrates a program that will add 5

numbers entered by the user. To print a program listing on the line printer, see LIST.

NOTE (NO.)

Format:

NOTE #aexp, avar, avar

Example:

100 NOTE #1, X, Y

This command is used to store the current disk sector number in the first avar and the current byte number within the sector in the second avar. This is the current read or write position in the specified file where the next byte to be read or written is located. This NOTE command is used when writing data to a disk file (see POINT). The information in the NOTE command is written into a second file which is then used as an index into the first file.

OPEN (0.)

CLOSE (CL.)

Formats:

OPEN #aexp,aexpl,aexp2, filespec

CLOSE gaexp

Examples: 100 OPEN #2,8,0,"D1:ATARI800.BAS"

100 A$ = "D1:ATARI800.BAS"

110 OPEN #2,8,0,A$

150 CLOSE #2

Before a device can be accessed, it must be opened. This "opening" process links a specific IOCB to the appropriate device handler, initializes any CIO-related control variables, and passes any device-specific options to the device handler. The parameters for the OPEN command are defined as follows: aexp

Mandatory character that must be entered by the user.

Reference IOCB or file number to same parameters for future use (as in CLOSE command). Nurnber rnay be 1 through 7.

26 1/0 Cornmands und

Devices

aexpl aexp2 filespec

Device

Code

Device

Number

(optional)

Code number to determine input or output Opera- tion.

Code 4 = input Operation

8 = output Operation

12 = input and output Operation

6 = disk directory input Operation

(In this case, the filespec is the search specification.)

9 = end-of-file append (output) operation. Append is also used for a special screen editor input mode.

This mode allows a program to input the next line from E: without waiting for the user to press

RETURN .

Device-dependent auxiliary code. An 83 in this parameter indicates sideways printing on a printer

(see appropriate manuals for control codes).

Specific file designation. Must be enclosed in quotation marks. The format for the filespec parameter is shown in Figure 5-2.

"D1 ATARI800.BAS"

,1%.m.mumiN

timi

A %saliN

Required

Colon

File name —

(up to 8 charactersmust begin with alphabet character)

Period requin as separator ii extender is us

Extender

(optional)-

Includes

0-3 characters

Note:

Filenames are not used with the program recorder.

Figure 5

2 Filename Breakdown

The CLOSE command simply closes flies that have been previously opened with an OPEN command. Note in the example that the aexp following the mandatory character must be the same as the aexp reference number in the OPEN statement.

Commands and Devices

POINT (P.)

Format:

POINT ilaexp, avar, avar

Example:

100 POINT #2, A,B

This command is used when reading a file into RAM. The first avar specifies the sector number and the second avar specifies the byte within that sector where the next byte will be read or written. Essentially, it moves a software-controlled pointer to the specified location in the file. This gives the user "random" access to the data stored on a disk file. The POINT and NOTE commands are discussed in more detail in the DOS Manual.

PRINT (PR

or ?)

Format:

PRINT [#aexp]i ; [exp] [,exp...]

Examples: PRINT X, Y, Z, A$

100 PRINT "THE VALUE OF X IS ";X

100 PRINT "COMMAS", "CAUSE", "COLUMN", "SPACING"

100 PRINT #3, A$

PUT(PU.)/

GET(GE.)

A PRINT command can be used in either Direct or Deferred mode. In Direct mode, this command prints whatever information is contained between the quotation marks exactly as it appears. In the first example, PRINT X,Y,Z,A$, the screen will display the current values of X,Y,Z, and A$ as they appear in the

RAM-resident program. In the last example, PRINT #3,A$, the #3 is the file specifier (may be any number between 1 and 7) that controls to which device the value of A$ will be printed. (See Input/Output Devices.)

A comma causes tabbing to the next tab location. Several commas in a row cause several tab jumps. A semicolon causes the next aexp or sexp to be placed immediately after the preceding expression with no spacing. Therefore, in the second example a space is placed before the ending quotation mark so the value of X will not be placed immediately after the word "IS". If no comma or semicolon is used at the end of a PRINT statement, then a

RETURN is output and the next PRINT will start on the following line.

Format:

PUT #aexp, aexp

GET gaexp,

Examples: 100 PUT #6, ASC("A")

200 GET #1,X

The PUT and GET are opposites. The PUT commandputputs a single byte from

0-255 to the file specified by #aexp. (# is a mandatory character in both these commands). The GET command reads one byte from 0-255 (using gaexp to designate the file, etc. on diskette or else -Where) and then stores the byte in the variable avar.

READ (REA.)

DATA (D.)

Formats:

READ var [ , var...]

DATA adata [ , adata...]

Examples: 100 READ A,B,C,D,E

110 DATA 12,13,14,15,16

100 READ A$,B$,C$,D$,E$

110 DATA EMBEE, EVELYN, CARLA, CORINNE, BARBARA

These two commands are always used together and the DATA statement is always used in Deferred mode'. The DATA statement can be located anywhere

'A Direct mode READ will only read data if a DATA statement was executed in the program.

1/0 Cornmands and Devices

\—

in the program, but must contain as many pieces of data as there are defined in the READ statement. Otherwise, an "out of data" error is displayed on the screen.

String variables used in READ statements must be dimensioned and cannot be subscripted. (See

STRINGS

Section). Neither may array variables may be used in a READ statement.

The DATA statement holds a number of string data for access by the READ statement. lt cannot include arithmetical operations, functions, etc. Furthermore, the data type in the DATA statement must match the variable type defined in the corresponding READ statement.

The following program totals a list of numbers in a DATA statement:

19 FÜR N=1 TO 5

20 READ 0

30 M=M+D

40 NEXT N

59 PRINT "SUM TOTAL EOUALS "iM

60 END

70 DATA 30,15,106,17,87

SAVE (S.)

STATUS (ST.)

MO (X.)

Figure 5-3 Read/Data Program Listing

The progran-1, when executed, will print the statement:

SUM TOTAL EQUALS 255.

Format:

Example:

SAVE filespec

SAVE "D1:YVONNE.PAT"

The SAVE command is similar to the CSAVE command except that the full file name System can be used. The device code number is optional when using only one disk drive. The default is to disk drive #1. SAVE, like LOAD, uses long interrecord gaps on the cassette (see

CSAVE)

and the tokenized form of the program.

Format:

Example:

STATUS #aexp,avar

350 STATUS #1,Z

The STATUS command calls the STATUS routine for the specified device (aexp).

The status of the STATUS command (see

ERROR MESSAGES,

Appendix B) is stored in the specified variable (avar). This may be useful for future devices such as the RS-232 interface.

Format:

XIO cmdno, #aexp, aexpl, aexp2, filespec

Example: XIO

18,#6,0,0,"S:"

The XIO command is a general input/output statement used for special operations. One example is its use to fill an area on the screen between plotted points

I/O Commands and Devices

and lines vvith a color (see Section 9). The parameters for this command are defined as follows: cmdno

Number that stands for the particular command to be performed.

cmdno OPERATION

254

OPEN

GET RECORD

GET CHARA.CTERS

PUT RECORD

PUT CHARACTERS

STATUS REQUEST

DRAW LINE

FILL

RENAME

DELETE

LOCK FILE

UNLOCK FILE

POINT

NOTE

FORMAT aexp

EXAMPLE

Same as BASIC OPEN

These 4 commands are similar to

BASIC INPUT GET, PRINT, and PUT respectively.

Same as BASIC CLOSE

Same as BASIC

STATUS

Same as BASIC DRAWTO

See Section 9

XIO 32,#1,0,0,"D:TEMP.CAROL"

XIO 33,#1,0,0,"D:TEMP.BAS"

XIO 35,#1,0,0,"D:TEMP.BAS"

XIO 36,#1,0,0,"D:TEMP.BAS"

Same as BASIC POINT

Same as BASIC NOTE

XIO 254,#1,0,0,"D2:"

Device number (same as in OPEN). Most of the time it is ignored, but must be preceded by #. aexpl aexp2

Two auxiliary control bytes. Their usage depends on the particular device and command. In most cases, they are unused and are set to 0. filespec String expression that specifies the device. Must be enclosed in quotation marks. Although some commands, like Fill (Section 9), do not look at the filespec, it must still be included in the statement.

CHAINING

PROGRAMS

I/O Commands and Devices

If a program requires more memory than is available, use the following steps to string programs of less than the maximum memory available into one program.

Type in the first part of the program in the normal way.

The last line of the first part of the program should contain only the line number and the command RUN"C:"

Cue the tape to the blank section. Write down the program counter number for later RUN purposes. Press PLAY and RECORD buttons on the deck so both remain down.

Type SAVE"C:" and press

RETURN

that

When the beeping sound occurs, press RETuRN again.

When the screen displays

"READY", do not move tape. Type NEW RETuRN .

Repeat the above instructions for the second part of the program.

As the second part of the program is essentially a totally new program, it is possible to re-use the line numbers used in the first part of the program.

If there is a third part of the program, make sure the last line of the second part is a RUN"C:" command.

To execute a "chained" program, use the following steps:

1. Cue the tape to the beginning of part 1 of the program.

Press PLAY button on the recorder.

Type RUN"C:"

RETURN

When the "beep" sounds, press

RETuRN again.

The computer automatically loads the first part of the program, runs it, and sounds a "beep" to indicate when to hit the space bar or

RETURN

to trigger the tape motor for the second LOAD/RUN. The loading takes a few seconds.

Note: A one-part program can be recorded and reloaded in the same way or

CSAVE and CLOAD can be used.

Note: Remember to boot DOS

before

typing in your program.

MODIFYING A

BASIC PROGRAM

ON DISK

The procedure for modifying an existing BASIC program stored on a diskette is demonstrated in the following steps:

1. Turn off ATARI console and insert BASIC cartridge.

Connect disk drive and turn it on - without inserting diskette.

Wait for Busy Light to go out and for the drive to stop. Open disk drive door.

Insert diskette (with DOS) and close door.

Turn on console. DOS should boot in and the screen show READY.

To load program from disk, type

LOAD "D:filename.ext

Modify program (or type in new program).

To save program on disk, type

SAVE "D:filename.ext

Always wait for the Busy light to go out before removing diskette.

10. To get a Directory listing, do not remove diskette and type

DOS

Upon

RETURN

the DOS Menu will be displayed. Select command letter

A, type it, and press

RETURN

twice to list the directory on the screen; or type

A followed by pressing

RETURN

then

RETURN

to list directory on the printer.

11. To return to BASIC, type

RETURN

or press

SYSTEM RESET

Commands and Devices

NOTES

Notes

6 FUNCTION

LIBRARY

This section describes the arithmetic, trigonometric, and special purpose functions incorporated into the ATARI BASIC. A function performs a computation and returns the result (usually a number) for either a print-out or additional computational use. Included in the trigonometric functions are two statements, radians (RAD) and degrees (DEG), that are frequently used with trigonometric functions. Each function described in this section may be used in either Direct or Deferred mode. Multiple functions are perfectly legal.

The following functions and statements are described in this section:

ABS

CLOG

EXP

INT

LOG

RND

SGN

SQ,R

ATN

COS

SIN

DEG/RAD

ADR

FRE

PEEK

POKE

USR

ARITHMETIC

FUNCTIONS

ABS

CLOG

EXP

INT

Format:

ABS(aexp)

Example:

100 AB = ABS (-190)

Returns the absolute value of a number without regard to whether it is positive or negative. The returned value is always positive.

Format:

CLOG (aexp)

Example:

100 C = CLOG(83)

Returns the logarithm to the base 10 of the variable or expression in parentheses. CLOG(0) should give an error and CLOG(1) should be 0.

Format:

EXP (aexp)

Example:

100 PRINT EXP(3)

Returns the value of e (approximately 2.71828283), raised to the power specified by the expression in parentheses. In the example given above, the number returned is 20.0855365. In some cases, EXP is accurate only to six significant digits.

Format:

INT (aexp)

Examples: 100 I = INT(3.445)

100 X = INT(- 14.66778)

(3 would be stored in I)

(-15 would be stored in X)

Function Library 33

LOG

RND

SGN

Returns the greatest integer less than or equal to the value of the expression.

This is true whether the expression evaluates to a positive or negative number.

Thus, in our first example above, I is used to store the number 3. In the second example, X is used to store the number - 15 (the first whole number that is less than or equal to — 14.66778). This INT function should not be confused with the function used on calculators that simply truncates (cuts off) all decimal places.

Format:

LOG(aexp)

Example:

100 L = LOG(67.89/2.57)

Returns the natural logarithm of the number or expression in parentheses.

LOG(0) should give an error and LOG(1) should be 0.

Format:

RND(aexp)

Example:

10 A = RND (0)

Returns a

hardware

generated random number between 0 and 1, but

never returns 1. The variable or expression in parentheses following RND is a dummy and has no effect on the numbers returned. However, the dummy variable must be used. Generally, the RND function is used in combination with other BASIC statements or functions to return a number for games, decision making, and the like. Here's a simple routine that returns a random number between 0 and 999.

10 X=RN0( )

20 RX= I NT( 1X)

39 PRINT RX

is dumm» variable)

Format:

Example:

SGN(aexp)

100 X = SGN(-199)

(-1 would be returned)

Returns a -1 if aexp evaluates to a negative number; a 0 if aexp evaluates to 0, or a

1 if aexp evaluates to a positive number.

Format:

Example:

SQR(aexp)

100 PRINT SR(100)

(10 would be printed)

Returns the square root of the aexp which must be positive.

TRIGONOMETRIC

FUNCTIONS

ATN

COS

Format:

ATN(aexp)

Example: 100 X = ATN(65)

Returns the arctangent of the variable or expression in parentheses.

Format:

COS(aexp)

Example:

100 C = COS(X Y + Z)

Note:

Presumes X, Y, Z previously defined!

Returns the trigonometric cosine of the expression in parentheses.

34 Function L,ibrary

SIN

DEG/RAD

Format:

SIN(aexp)

Example:

100 X = SIN(Y)

Note:

Presumes Y previously defined.

Returns the trigonometric sine of the expression in parentheses.

Format:

DEG

RAD

Example:

100 DEG

100 RAD

These two statements allow the programmer to specify degrees or radians for trigonometric function computations. The computer defaults to radians unless

DEG is specified. Once the DEG statement has been executed, RAD must be used to return to radians.

See Appendix E for the additional trigonometric functions that can be derived.

SPECIAL

PURPOSE

FUNCTIONS

ADR

FRE

PEEK

POKE

Format:

ADR(svar)

Example:

ADR(A$)

Returns the decimal memory address of the string specified by the expression in parentheses. Knowing the address enables the programmer to pass the information to USR routines, etc. (See USR and Appendix D)

Format:

FRE(aexp)

Examples: PRINT FRE (0)

100 IF FRE (0) < 1000 THEN PRINT "MEMORY CRITICAL"

This function returns the number of bytes of user RAM left. Its primary use is in

Direct mode with a dummy variable (0) to inform the programmer how much memory space remains for completion of a program. Of course FRE can also be used within a BASIC program in Deferred mode.

Format: PEEK(aexp)

Examples: 1000 IF PEEK (4000) = 255 THEN PRINT "255"

100 PRINT "LEFT MARGIN IS"; PEEK (82)

Returns the contents of a specified memory address location (aexp). The address specified must be an integer or an arithmetic expression that evaluates to an integer between 0 and 65535 and represents the memory address in decimal notation (not hexadecimal). The number returned will also be a decimal integer with a range from 0 to 255. This function allows the user to examine either RAM or

ROM locations. In the first example above, the PEEK is used to determine whether location 4000 (decimal) contains the number 255. In the second example, the PEEK function is used to examine the left margin.

Format:

POKE aexpl, aexp2

Examples: POKE 82, 10

100 POKE 82, 20

Function Library 35

USR

Although this is not a function, it is included in this section because it is closely associated with the PEEK function. This POKE command inserts data into the memory location or modifies data already stored there. In the above format, aexpl is the decimal address of the location to be poked and aexp2 is the data to be poked. Note that this number is a decimal number between 0 and 255. POKE cannot be used to alter ROM locations. In gaining familiarity with this command it is advisable to look at the memory location with a PEEK and write down the contents of the location. Then, if the POKE doesn't work as anticipated, the original contents can be poked into the location.

The above Direct mode example changes the left screen margin from its default position of 2 to a new position of 10. In other words, the new margin will be 8 spaces to the right. To restore the margin to its normal default position, press

SYSTEM RESET •

Format:

USR (aexpl [, aexp2][, aexp3...])

Example: 100 RESULT = USR (ADD1,A*2)

This function returns the results of a machine-language subroutine. The first expression, aexp1, must be an integer or arithmetic expression that evaluates to an integer that represents the decimal memory address of the machine language routine to be performed. The input arguments aexp2, aexp3, etc., are optional.

These should be arithmetic expressions within a decimal range of 0 through

65535. A non-integer value may be used; however, it will be rounded to the nearest integer.

These values will be converted from BASIC's Binary Coded Decimal (BCD) floating point number format to a two-byte binary number, then pushed onto the hardware stack, composed of a group of RAM memory locations under direct control of the 6502 microprocessor chip. Figure 6-1 illustrates the structure of the hardware stack.

(Number of arguments on the stack-may be 0)

(High byte of argument X)

(Low byte of argument X)

(High byte of argument Y)

(Low byte of argument Y)

(High byte of argument Z)

(Low byte of argument Z)

R i

R 2

(Low byte of return address)

(High byte of return address)

Figure 6-1. Hardware Stock Definition

Note:

X is the argument following the address of the routine, Y is the second, Z is the third, etc. There are N pairs of bytes.

See Section 11 for a description of the USR function in machine language programming. Appendix D defines the bytes in RAM available for machine language programming.

36 Function Librcuy

STRINGS

ASC

CHRS

This section describes strings and the functions associated with string handling.

Each string must be dimensioned (see DIM statement, Section 8) and each string variable must end with a $. A string itself is a group of characters "strung" together. The individual characters may be letters, numbers, or symbols

(including the Atari special keyboard symbols.) A substring is a part of a longer string and any substring is accessible in Atari BASIC if the string has been properly dimensioned (see end of section). The characters in a string are indexed from 1 to the current string length, which is less than or equal to the dimensioned length of the string.

The string functions described in this section are:

ASC STR$

CHR$

VAL

LEN

Format:

ASC(sexp)

Examples: 100A = ASC(A$)

This function returns the ATASCII code number for the first character of the string expression (sexp). This function can be used in either Direct or Deferred mode. Figure 7-1 is a short program illustrating the ASC function.

10 D1M A$(3)

20 A$="E"

30

A=A51:( A$ )

49 PRINT A

Figure

7-1.

ASC Function Program

When executed, this program prints a 69 which is the ATASCII code for the letter "E". Note that when the string itself is used, it must be enclosed in quotation marks.

Format:

CHR$ (aexp)

Examples:

100

PRINT CHR$ (65)

100 A$ = CHR$ (65)

This character string function returns the character, in string format, represented by the ATASCII code number(s) in parentheses. Only one character is returned. In the above examples, the letter A is returned. Using the ASC and

CHR$ functions, the following program prints the upper case and lower case letters of the alphabet.

Strings

LEN

STR$

VAL

In

FÜR. I=0 TO 25

pp.:INT

ASC( "A"

I )

NEXT I

CHRS( Pi'7:f2( "

Figure 7-2. ASC and CHRS Program Example

Note: There can be only one STR$ and only one CHR$ in a logical comparison.

Format:

LEN (sexp)

Example:

100 PRINT LEN(A$)

This function returns the length in bytes of the designated string. This information may then be printed or used later in a program. The length of a string variable is simply the index for the character which is currently at the end of the string. Strings have a length of 0 until characters have been stored in them. lt is possible to store into the middle of the string by using subscripting.

However, the beginning of the string will contain garbage unless something was stored (using STO) there previously.

The following routine illustrates one use of the LEN function:

10 DIM A$(10)

20 AS-= ATARI "

30 RIR I!

.1T LEN( A$ )

Figure 7-3. LEN Function Example

The result of running the above program would be 5.

Format:

STR$ (aexp)

Example:

A$ =STR$(65)

This string from number function returns the string form of the number in parentheses. The above example would return the actual number 65, but it would be recognized by the computer as a string.

Note: There can only be one STR$ and only one CHR$ in a logical comparison.

For example, A =STR$(1) > STR$(2) is not valid and will not work correctly.

Format: VAL(sexp)

Example:

100 A = VAL(A$)

This function returns a number of the same value as the number stored as a string. This is the opposite of a STR$ function. Using this function, the computer can perform arithmetic operations on strings as shown in the following example program:

10 DIM B$(5)

20 24= 11 10000"

30 B=SOROJAL(B$))

40 PRINT "THE SQUARE ROOT OF "Jae," IS "

Figure 7-4. VAL Function Program

Strings

Upon execution, the screen displays THE SQUARE ROOT OF B$ IS 100. lt is not possible to use the VAL function with a string that does not start with a number, or that cannot be interpreted by the computer as a number. lt can, however, intrepret floating point numbers; e.g.,VAL ("1E9")would return the number 1,000,000,000.

STRING

MANIPULATIONS

Strings can be manipulated in a variety of ways. They can be split, concatenated, rearranged, and sorted. The following paragraphs describe the different manipulations.

String Concatenation

Concatenation means putting two or more strings together to form one large string. Each string to be included in a larger string is called a substring. Each substring must be dimensioned (see DIM). In Atari BASIC, a substring can contain up to 99 characters (including spaces). After concatenation, the substrings can be stored in another string variable, printed, or used in later sections of the

=program. Figure 7-5 is a sample program demonstrating string ccincatenation.

In this program, A$, B$, and C$ are concatenated and placed in A$.

10 DIM A$(100),B$(100),C$(100)

20 AS="STRINGS 2, SUESTRINGS ARE DISCUSSE

D "

30 E:$" IN 'ATARI BASIC--A SELF-TEACHING

GUIDE'"

40 C="---CHAPTER 9."

50 E

LEN( AS )+

1

>=B$

60 4( LEW ..J+1 )=CS

70 PRINT AS

Figure 7-5. String Concatenation Example

String Splitting

The format of a subscript string variable is as follows: svarname(aexpl[ ,aexp2])

The svarname is used to indicate the unsubscripted string variable name (with

$). aexpl indicates the starting location of the substring and aexp2 (if used) indicates the ending location of the substring. If no aexp2 is specified, then the end of the substring is the current end of the string. The starting location cannot be greater than the current length of the string. The two example programs in

Figure 7-6 illustrate a split string with no end location indicated and a split string with an ending location indicated.

10 DIM SS(5)

20 5$=" PIECE*"

33 PRINT SV

2::

40 END •

Result is BCD.

(without ending location)

10 DIM SS(20)

20 SS="ATARI 200 BASIC"

30 PRINT SE 7, 9 )

40 END

Result is 800.

(with ending location)

Figure 7-6. Split String Examples

Strings 39

St rings

String Comparisons and Sorts

In string comparisons, the logical operators are used exactly the way they are with numbers. The second program in Appendix H is a simple example of bubble sort.

In using logical operators, remember that each letter, number, and symbol is assigned an ATASCII code number. A few general rules apply to these codes:

ATASCII codes for numbers are sized in order of the numbers' real values and are always lower than the codes for letters (see Appendix C).

Upper case letters have lower numerical values than the lower case letters. To obtain the ATASCII code for a lower case letter if you know the upper case value, add 32 to the upper case code.

Note:

Atari 13ASIC's rnemory management system moves strings - around in memory to make room for new statements. This causes the string address to vary if a program is modified or Direct mode is used.

8 ARRAYS AND

MATRICES

DIM (DI.)

An array is a one-dimensional list of numbers assigned to subscripted variables; e.g., A(0), A(1), A(2). Subscripts range from 0 to the dimensioned value. Figure

8-1 illustrates a 7-element array.

A(0)

A(1)

A(2)

A(3)

A(4)

A(5)

A(6)

Figure 8-1. Example of an Array

A matrix, in this context, is a two-dimensional table containing rows and columns. Rows run horizontally and columns run vertically. Matrix elements are stored by BASIC in row-major order. This means that all the elements of the first row are stored first, followed by all the elements of the second row, etc.

Figure 8-2 illustrates a 7 x 4 matrix.

Columns

M(0,0)

M(1,0)

M(2,0)

M(3,0)

M(4,0)

M(5,0)

M(6,0)

M(0,1)

M(1,1)

M(2,1)

M(3,1)

M(4,1)

M(5,1)

M(6,1)

M(0,2)

M(1,2)

M(2,2)

M(3,2)

M(4,2)

M(5,2)

M(6,2)

M(0,3)

M(1,3)

M(2,3)

M(3,3)

M(4,3)

M(5,3)

M(6,3)

Figure 8-2. Example of a Matrix

This section describes the two commands associated with arrays, matrices, and strings, and how to load both arrays and matrices. The commands in this section are:

DIM

CLR

Format:

Dim svar(aexp) 1 I ,svar(aexp) mvar(aexp[ ,aexp]) I 1 ,mvar(aexp [ ,aexp •••

ExampIes:

DIM A(100)

DIM M(6,3)

DIM B$(20) used with STRINGS

Arrays and Matrices

42 Arrays and Matrices

A DIM statement is used to reserve a certain number of locations in memory for a string, array, or matrix. A character in a string takes one byte in memory and a number in an array takes six bytes. The first example reserves 101 locations for an array designated A. The second example reserves 7 rows by 4 columns for a two-dimensional array (matrix) designated M. The third example reserves

20 bytes designated B$.

All strings, arrays, and matrices must be dimensioned.

lt is a good habit to put all DIM statements at the beginning of the program. Notice in Figure 8-1 that although the array is dimensioned as DIM A(6), there are actually 7 elements in the array because of the 0 element. Although

Figure 8-2 is dimensioned as DIM M(6,3), 28 locations are reserved.

Note:

The ATARI Personal Computer does not automatically initialize array or matrix variables to

0 at the start of program execution. To initialize array or matrix elements to 0, use the following program steps:

259 °IM A(100)

390 FÜR E=0 TO 100

319 A(E)=0

320 NEXT E

Arrays and matrices are "filled" with data by using

FOR/NEXT statements,

READ/DATA statements and INPUT commands. Figure 8-3 illustrates the

"building" of part of an array using the FOR/NEXT loop and

Figure

84 builds an array using the READ/DATA statements.

10 DIM A(100

20 X=10

70 FÜR E=1 TO 90

40 X=X+1

50 A(E)=X

60 NEXT E

70 FÜR P=1

TO 90

0 PRINT E,A(E)

90 NEXT

Figure 8-3. Use of FOR/NEXT to Build An Array

10 °IM A(3)

20 FÜR E=1 TO 3

30 READ X

40 i(E)=X

59 PRINT A( E),

60 NEXT E

70 END

100 DATA 33,45,12

Figure 8-4. Use of READ/DATA to Build An Array

CLR

Figure 8-5 shows an example of building a 6 x 3 matrix.

10 EIIM M6,3)

:20 FÜR ROW=0 TO G

30 FÜR COL.1 TO 7

40 WROW,COL)=INT(RNO(0)1000)

50 NEXT COUNEXT ROW

60 FÜR ROW=0 TO 6

70 FÜR COL.1 TO 3

80 PRINT WROW,COL>

90 NEXT COL , PRINT sNEXT ROW

Figure 8-5. Building A Matrix

Note that the words ROW and COLUMN are not BASIC commands, statements, functions, or keywords. They are simply variable names used here to designate which loop function is first. The program could just as easily have been written with X and Y as the variable names.

Format:

Example:

CLR

200 CLR

This command clears the memory of all previously dimensioned strings, arrays, and matrices so the memory and variable names can be used for other purposes. lt also clears the values stored in undimensioned variables. If a matrix, string, or array is needed after a CLR command, it must be redimensioned with a DIM command.

Arrays und Muttiees 43

NOTES

Notes

9 GRAPHICS MODES

AND COMMANDS

This section describes the Atari BASIC commands and the different graphics modes of the ATARI Personal Computer. Using these commands, it is possible to create graphics for game, graphics, and patterns.

The commands to be described in this section are:

GRAPHICS

COLOR

DRAWTO

LOCATE

PLOT

POSITION

PUT/GET

SETCOLOR

XIO

The PUT/GET and XIO commands explained in this section are special applications of the same commands described in Section 5.

GRAPHICS (GR.)

Format:

GRAPHICS aexp

Example: GRAPHICS 2

This command is used to select one of the nine graphics modes. Table 9-1 summarizes the nine modes and the characteristics of each. The GRAPHICS command automatically opens the screen, S:(the graphics window),as device #6. So when printing text in the text window, it is not necessary to specify the device code. The aexp must be positive, rounded to the nearest integer. Graphics mode

0 is a full-screen display while modes 1 through 8 are split screen displays. To override the split-screen, add the characters + 16 to the mode number (aexp) in the GRAPHICS command. Adding 32 prevents the graphics command from clearing the screen.

To return to graphics mode 0 in Direct mode, press and press

RETURN .

or type GR.0

TABLE 9.1—TABLE OF MODES AND SCREEN FORMATS

Gr.

Mode

Type

SCREEN FORMAT

Verl.

Horiz.

(Hours)

(Col)

Split

(Col)

Full

Screen Screen

Number

Colors

RAM

Required

(Bytes)

TEXT

GRAPHICS

160

320

160

192

The following paragraphs describe the nine graphics modes.

1/2

993

513

261

273

537

1017

2025

3945

7900

Graphic Müdes and Commands

GRAPHICS

MODE 0

GRAPHICS

MODE S

1 AND 2

This mode is the 1-color, 2-luminance (brightness) default mode for the ATARI

Personal Computer. lt contains a 24 by 40 character screen matrix. The default margin settings at 2 and 39 allow 38 characters per line. Margins may be changed by poking LMARGN and RMARGN (82 and 83). See Appendix I. Some systems have different margin default settings. The color of the characters is determined by the background color. Only the luminance of the characters can be different.

This full-screen display has a blue display area bordered in black (unless the border is specified to be another color). To display characters at a specified location, use one of the following two methods.

Method 1. lineno POSITION aexp1, aexp2 lineno PRINT sexp

Puts cursor at location specified by aexpl and aexp2.

Method 2 lineno GR. 0 lineno POKE 752,1 lineno COLOR ASC(sexp) lineno PLOT aexp1,aexp2 lineno GOTO lineno

Specifies graphics mode.

Suppresses cursor.

Specifies character to be printed.

Specifies where to print character.

Start loop to prevent READY from being printed. (GOTO same lineno.)

Press

BREAK

to terminate loop.

GRAPHICS 0 is also used as a clear screen command either in Direct mode or

Deferred mode. lt terminates any previously selected graphics mode and returns the screen to the default mode (GRAPHICS 0).

As defined in Table 9-1, these two 5-color modes are Text modes. However, they are both split-screen (see Figure 9-1) modes. Characters printed in Graphics mode 1 are twice the width of those printed in Graphics 0, but are the same height. Characters printed in Graphics mode 2 are twice the width and height of those in Graphics mode 0. In the split-screen mode, a PRINT command is used to display characters in either the text window or the graphics window. To print characters in the graphics window, specify device #6 after the PRINT command.

Example:

100 GR. 1

110 PRINT46;"ATARI”

The default colors depend on the type of character input. Table 9-2 defines the default color and color register used for each type.

Table 9-2. Default Colors for Specific Input Types

Character Type

Upper case alphabetical

Lower case alphabetical

Inverse upper case alphabetical

Inverse lower case alphabetical

Numbers

Inverse numbers

Color Register Default Color

Note: See SETCOLOR to change character colors.

Orange

Light Green

Dark Blue

Red

Orange

Dark Blue

46 Graphic Modes and Commands

Unless otherwise specified, all characters are displayed in upper case noninverse form. To print lower case letters and graphics characters, use a POKE

756,226. To return to upper case, use POKE 756,224.

In graphics modes 1 and 2, there is no inverse video, but it is possible to get all the rest of the characters in four different colors (see end of section).

(X=0)

(Y=0)

Graphics Window

(graphies or test)

Text Window lines) border (size depends on individual

TV's overscan)

Figure 9-1. Split-Screen Display For Graphics Modes 1 and

The X and Y coordinates start at 0 (upper left of screen). The maximum values are the numbers of rows and columns minus 1 (see Table 9-1).

This split-screen configuration can be changed to a full screen display by adding the characters + 16 to the mode number.

Example:

GRAPHICS 1+16

GRAPHICS

MODES

3, 5, AND 7

These three 4-color graphics modes are also split-screen displays in their default state, but may be changed to full screen by adding +16 to the mode number.

Modes 3, 5, and 7 are alike except that modes 5 and 7 use more points (pixels) in plotting, drawing, and positioning the cursor; the points are smaller, thereby giving a much higher resolution.

GRAPHICS

These two 2-color graphics modes are split-screen displays and can display in

MODES only two colors while the other modes can display 4 and 5 colors. The advantage of a two-color mode is that it requires less RAM space (see Table 9-1). Therefore,

4 AND 6 it is used when only two - colors are needed and RAM is getting crowded. These two modes also have a higher resolution which means smaller points than

Graphics mode 3.

GRAPHICS

MODE 8

This graphics mode gives the highest resolution of all the other modes. As it takes a lot of RAM to obtain this kind of resolution, it can only accomodate a maximum of one color and two different luminances.

Graphie Modes and Connnands

COLOR (C.)

Format:

Examples:

COLOR aexp

110 COLOR ASC("A")

110 COLOR 3

The value of the expression in the COLOR statement determines the data to be stored in the display memory for all subsequent PLOT and DRAWTO commands until the next COLOR statement is executed. The value must be positive and is usually an integer from 0 through 255. Non-integers are rounded to the nearest integer. The graphics display hardware interprets this data in different ways in the different graphics modes. In text modes 0 through 2, the number can be from 0 through 255 (8 bits) and determines the character to be displayed and its color. (The two most significant bits determine the color. This is why only 64 different characters are available in these modes instead of the full

256-character set.)

Tables 9-6 and 9-7 at the end of this section illustrate

the internal character set and the character/color

assignment. Tahle 9-2 is a simplified table which allows easy generation of some of the colors. For example,

COLOR ASC("A"): PLOT

5,5

will display an

orange

A character in graphics modes 1 or 2 at location 5,5.

Graphics modes 3 through 8 are not text modes, so the data stored in the display

RAM simply determines the color of each pixel. Two-color or two-luminance modes require either 0 or 1 (1-bit) and four-color modes require 0, 1, 2, or 3. (The expression in the COLOR statement may have a value greater than 3, but only one or two bits will be used.) The actual color which is displayed depends on the value in the color register which corresponds to the data of 0, 1, 2, or 3 in the particular graphics mode being used. This may be determined by looking in

Table 9-5, which gives the default colors and the corresponding register numbers. Colors may be changed by using SETCOLOR.

Note that when BASIC is first powered up, the color data is 0, and when a

GRAPHICS command (without + 32) is executed, all of the pixels are set to 0.

Therefore, nothing seems to happen to PLOT and DRAWTO in GRAPHICS 3 through 7 when no COLOR statement has been executed. Correct by doing a .

COLOR 1 first.

DRAWTO (DR.)

Format:

DRAWTO aexpl, aexp2

Example:

100 DRAWTO 10, 8

This statement causes a line to be drawn from the last point displayed by a PLOT

(see

PLOT)

to the location specified by aexpl and aexp2. The first expression represents the X coordinate and the second represents the Y-coordinate (see

Figure 9-1). The color of the line is the same color as the point displayed by the

PLOT.

LOCATE (LOC.)

Format:

LOCATE aexpl, aexp2, var

Example:

150 LOCATE 12, 15, X

This command positions the invisible graphics cursor at the specified location in the graphics window, retrieves the data at that pixel, and stores it in the specified arithmetic variable. This

gives

a• number from 0 to 255 for Graphics modes 0 through 2; 0 or 1 for the 2-color graphics modes; and 0, 1, 2, or 3 for the

4-color modes. The two arithmetic expressions specify the X and Y coordinates

of the

point. LOCATE is equivalent to:

POSITION aexp1, aexp2:GET #6,avar

Graphic Modes and Commands

■

..__

Doing a PRINT after a LOCATE or GET from the screen may cause the data in the pixel which was examined to be modified. This problem is avoided by repositioning the cursor and putting the data that was read, back into the pixel before doing the PRINT. The following program illustrates the use of the

LOCATE command.

10 GRAPHICs 7+16

29 coLoR

30 GETCOLOP 2,10,8

40 PLOT 10,15

50 DRANTO 15,15

60 LOCATE 12,15 X

70 PRINT X

Figure 9-2. Example Program Using LOCATE

PLOT (PL.)

On execution, the program prints the data (1) determined by the COLOR statement which was stored in pixel 12, 15.

Format:

PLOT aexpl, aexp2

Example:

100 PLOT 5,5

The PLOT command is used in graphics modes 3 through 8 to display a point in the graphics window. The aexpl specifies the X-coordinate and the aexp2 the

Y-coordinate. The color of the plotted point is determined by the hue and luminance in the color register from the last COLOR statement executed. To change this color register, and the color of the plotted point, use SET-

COLOR. Points that can be plotted on the screen are dependent on the graphics mode being used. The range of points begins of 1 and extends to one less than the total number of rows (X-coordinate) or columns (Y-coordinate) shown in

Table 9-1.

POSITION

(POS.) Format:

POSITION aexpl, aexp2

Example:

100 POSITION 8, 12

PUT/GET

PU /GE)

The POSITION statement is used to place the invisible graphics window cursor at a specified location on the screen (usually precedes a PRINT statement). This statement can be used in all modes. Note that the cursor does not actually move until an I/O command which involves the screen is issued.

Formats:

PUT #aexp, aexp

GET #aexp, avar

Examples: 100 PUT #6, ASC("A")

200 GET #1, X

In graphics work, PUT is used to output data to the screen display. This statement works hand-in-hand with the POSITION statement. After a PUT (or GET), the cursor is moved to the next location on the screen.

Doing a PUT to device causes the one-byte input (second aexp) to be displayedaat the cursor position.

The byte is either an ATASCII code byte for a particular character (modes 0-2) or the color data (modes 3-8).

GET is used to input the code byte of the character displayed at the cursor tion, into the specified arithmetic variable. The values used in

PUT and GET correspond to the values in the COLOR statement. (PRINT and INPUT may also be used.)

Graphic Müdes arid Cornmands

Note:

Doing a PRINT after a LOCATE or GET from the screen may cause the data in the pixel which was examined to be modified. To avoid this problem, reposition the cursor and put the data that was read, back into the pixel before doing the PRINT.

SETCOLOR (SE.)

Format:

SETCOLOR aexpl, aexp2, aexp3

Example:

100 SETCOLOR 0, 1, 4

This statement is used to choose the particular hue and luminance to be stored in the specified color register. The parameters of the SETCOLOR statement are defined below: aexpl = Color register (0-4 depending on graphics mode) aexp2 = Color hue number (0-15. See Table 9-3) aexp3 = Color luminance (must be an even number between 0 and 14; the higher the number, the brighter the display. 14 is almost pure white.)

TABLE 9.3—THE ATARI HUE (SETCOLOR COMMAND)

NUMBERS AND COLORS

COLORS SETCOLOR (aexp2) NUMBERS

GRAY

LIGHT ORANGE (GOLD)

ORANGE

RED-ORANGE

PINK

PURPLE-BLUE

BLUE

LIGHT BLUE

TURQUOISE

GREEN-BLUE

GREEN

YELLOW-GREEN

ORANGE-GREEN

LIGHT ORANGE

Note:

Colors will vary with type and adjustment of TV or monitor used.

The ATARI display hardware contains five color registers, numbered from 0 through 4. The Operating System (OS) has five RAM locations (COLOR° through COLOR4, see Appendix I - Memory Locations) where it keeps track of the current colors. The SETCOLOR statement is used to change the values in these RAM locations. (The OS transfers these values to the hardware registers every television frame.) The SETCOLOR statement requires a value from 0 to 4 to specify a color register. The COLOR statement uses different numbers because it specifies data which only indirectly corresponds to a color register.

This can be confusing, so careful experimentation and study of the various tables in this section is advised.

No SETCOLOR commands are needed if the default set of five colors is used.

Although 128 different color-luminance combinations are possible, not more than five can be displayed at any one time. The purpose of the color registers and SETCOLOR statement is to specify these five colors.

Graphic Modes and Gornmonds

TABLE 9.4—TABLE OF SETCOLOR "DEFAULT" COLORS*

Setcolor

(Color Register)

Defaults To

Color

Luminance

Actual Color

ORANGE

GREEN

DARK BLUE

PINK OR RED

BLACK

'DEFAULT" occurs if not SETCOLOR statement is used.

Note:

Colors may vary depending upon the television monitor type, condition, and adjustment.

A program illustrating Graphics mode 3 and the commands explained so far in this section is shown below:

10 GRAPHICS 3

20 RETCOLOR 0,

2 ,8:C3LOR 1

39 PLOT 17,1 , DRAWTO 17,12 , DRAWTO 9,12

40 PLOT 19,1 , 0RAWT0 19,12

59 PLOT 20,1:DRAWTO 20,12

60 PLOT 22,1:0RAWTO 22,10:DRAWTO 30,18

70 POKE 752,1

89 PRINT :PRINT " ATARI PER2ONAL COMP

UTERS"

90 GOTO '

The SETCOLOR and COLOR statements set the color of the points to be plotted

(see Table 9.5). The SETCOLOR command loads color register 0 with hue 2

(orange) and a luminance of 8 ("normal"). The next 4 lines plot the points to be displayed. Line 90 suppresses the cursor and line 100 prints the string expression

ATARI PERSONAL COMPUTERS in the text window (6 spaces in).

Note that the background color was never set because the default is the desired color (black).

If the program is executed, it will print the Atari logo in the graphics window and the string expression in the text window as in Figure 9-3.

Graphie Modes and Connnands

■

•1

Y-AXIS POINTS (ROWS)

•.• GA u

o \

Cle

n

x z0.91 z

Graphic Modes and Comtnands

2 <

'c-- e i-g eiD t,1 >.

Z o

(.2

FIZ

E-1

X cl) cu

GJ o

Cö

5 z e

110

0 ct

(1)

PZI

5 cu

-0

Z z ,

-1--

■ 0

C15 bp

;....

C Q

U r...,

1 urza im

C-

■

-0

.4.-i-i-o-4 ■ 4-.0

U U 0 U S.

C13 CCS CO

Ct 110 cz cu czi ccs c..,

,-O

4 .4 4 cu uuu,c.)gcl o o o

UUU

''''' '.'" • ""

•'-1 ni ns c,:, cr, s-. ;-. s-. . s-.

LDULD ic..7 bi)

.- -

Cö e ho

,- .

CCS e

•1-.

0 a,

• 0

■ cr,

;-. , ct u

C.7 i 1 Ic..7

'1:5

3 cu

Z ow co0 ru '2, m -c-d -ätt

0 ce ci) ,_ _0 m cu

4 ce • c --

,-zi tj o t Cr.; -4-

0 t +8'

0 —, s■

Tzi M

Ü U

,-, r.,“,"D . 0

0 bt

,-- c‘I

..ID rn ce

0 .-.

8 3 cU c4-.

E ',25' up mj os ho

._.

ä CCd

0 U

P. -

0 cci ce L.

;-. u , 0

S...7 (...7 I M

0 >,u=. C1J

E• 0

3 U 'El cn

cD .-1 c•2 cn 714

CD ex

-ci

r

c/D ce g >

0 4 0 c 4 z

0 ,--1 c9 cn e 0

■ ■ c \t on e

0 1-1 CN/ CO 0 0 1-1 r \/ Cr) e iii

-0

0 c' ;‹ in' i...

1-.1 r•-

■

Q cz z >

■ n

0 ° 0

0 os >

ci)

0L)

4... z

Z 41

■

P4 ;4

4 4

M t4 C-3

E-4 <

:1 t=1

Z gq

P4 p_l

0 1:: 4

Z0 M CZ C-)

< r

_ „,4 `I

12P

U...7

722 2

Z 4

2 tz

ZC.D P:1 C-)

< E_, <

P:1 n

F.0

L..)

PZ1

4.1 4.1 g4

4 c O3

,_,

0 < il 2

121

Graphie Modes and Command.s

XIO (X.)

SPECIAL FILL

APPLICATION

Format:

XIO 18, #aexp, aexpl, aexp2, filespec

Example:

100 XIO 18, #6, 0, 0, "S:"

This special application of the XIO statement fills an area on the screen between plotted points and lines with a non-zero color value. Dummy variables (0) are used for aexpl and aexp2.

The following steps illustrate the fill process:

PLOT bottom right corner (point 1).

DRAWTO upper right corner (point 2). This outlines the right edge of the area to be filled.

DRAWTO upper left corner (point 3).

POSITION cursor at lower left corner (point 4).

POKE address 765 with the fill color data (1, 2, or 3).

This method is used to fill each horizontal line from top to bottom of the specified area. The fill starts at the left and proceeds across the line to the right until it reaches a pixel which contains non

zero data (will wraparound if necessary). This means that fill cannot be used to change an area which has been filled in with a non-zero value, as the fill will stop. The fill commänd will go into an infinite loop if a fill with zero (0) data is attempted on a line which has no non-zero pixels.

BREAK

SYSTEM RESET

can be used to stop the fill if this happens.

The following program creates a shape and fills it with a data (color) of 3. Note that the XIO command draws in the lines of the left and bottom of the figure.

10 GRAPHICS 5÷16

20 COLOR 3

33 PLOT 70, 45

40 DRAWTO 50, 10

50 DRAWTO 30, 10

60 POSITION 113.45

70 POKE 765,

80 0 18, #6, 0, 0. "

90 GoTo

Figure 9-4. Example "FILL" Program

Assigning Colors To Characters In Text Modes 1 and 2

This procedure describes the method of assigning colors to the Atari character set. First, look up the character number in Table 9-6. Then, see Table 9-7 to get the conversion of that number required to assign a color register to it.

Example:

Assign SETCOLOR 0 to lower case "r" in mode 2 whose color is determined by register 0.

In Table 9-6, find the column and number for "r" (114-column 4).

Using Table 9-7, locate column 4. Conversion is the character'number minus

32 (114 - 32 = 82).

Graphic Modes und

COM171alldS

' X

VD -

Z >

›-

—

IC V

Ah.

T u c9

, e

1-4

1-1

,-4

CZ ,-0 C.) up

1-1

1-4

.-1

1-1 co

1-1

7:5 (1) 4-1

0-) x-4

1-1

0 c9

1-1

—I

'-'

IV) ,-.

•---. c-9 c9

7t• c-9

.-i

••--

N o

0 oc)

0 o o

.-I

-4

.--

■ c9 o

.--4

..-1 e

.--1

Li-D

,--4

,-,

N-

-1 co

-, o

-1

1-1

•I

U ce tt

E z o r4

0 co

.--

■ co r9 co

-:}4

Co in

: t--

(20

Co o

,-( cs) c-q

0 e

N. lt>

el 3 113 E

1 -1

N-

E z

G.7 et

r4 z

c•

'Zt 4

T-4 li D

f2:1 z..)

tt c9

Cr)

In co in e

In in in

(..0 irD

(Z1 P4 V.1-

■ co co

"el

CO in

CO CO c0

,....

■

— -- —

N in oC

0")

•,

-1

< 1

> Z 0

Cr)

0 e

1 e

C9 e

Cr) e e e

In e cm ei

U o

1-1 le

,-,

,..› c g-i

,--i c9

-1

.-1

("9

•sti

1-4

N c•9

N e

11-3

•En_ ,,f2

1 in c.ID

LCD

t--- CC

N- c0

—

• •

• -

V c..0

N-

0 0

,.-1

,-(

,.-+ c-.1

1-4

I I A cs-.

■

9-1

....,_

trp

1-1

Graphic Modes and Cominands

MODE 0

MODE 1

MODE 2

TabIe 9.7—CHARACTER/COLOR ASSIGNMENT

Conversion 1 Conversion 2 Conversion 3 Conversion 4

SETCOLOR 2

11+32

# + 32

11-32

NONE

POKE 756,224

POKE 756,226

# + 32 11-32

SETCOLOR 0

SETCOLOR 1

-$32

NONE

11-32

11-64

# + 160

#+ 64

# + 160

NONE

11+96

SETCOLOR 2

SETCOLOR 3

# + 128 11+ 192

# + 96

# + 64

# +

128

2. Luminance controlled by SETCOLOR 1, 0, LUM.

POKE the Character Base Address (CHBAS) with 226 to specify lower case letters or special graphics characters; e.g.,

POKE 756,226 or

CHBAS = 756

POKE CHBAS, 226

To return to upper case letters, numbers, and punctuation marks, POKE CHBAS with 224.

A PRINTstatement using the converted number (82) assigns the lower case

"r" to SETCOLOR 0 in mode 2 (see Table 9-5).

Graphic Control Characters

These characters are produced when the

EZ3

key is pressed with the alphabetic keys shown on back cover. These characters can be used to draw design, pictures, etc., in mode 0 and in modes 1 and 2 if CHBAS is changed.

56 Graphic Modes and Conimands

10 SOUNDS AND GAME

CONTROLLERS

SOUND (SO.)

This section describes the statement used to generate musical notes and sounds through the audio System of the television monitor. Up to four different sounds can be "played" simultaneously creating harmony. This SOUND statement can also be used to simulate explosions, whistles, and other interesting sound effects. The other commands described in this section deal with the functions used to manipulate the keyboard, joystick, and paddle controllers. These functions allow these controllers to be plugged in and used in BASIC programs for games, etc.

The command and functions covered in this section are:

SOUND PADDLE

PTRIG

STICK

STRIG

Format:

SOUND aexpl, aexp2, aexp3, aexp4

Example:

100 SOUND 2, 204, 10, 12

The SOUND statement causes the specified note to begin playing as soon as the statement is executed. The note will continue playing until the program encounters another SOUND statement with the same aexpl or an END statement.

This command can be used in either Direct or Deferred modes.

The SOUND parameters are described as follows: aexpl =

Voice. Can be 0-3, but each voice requires a separate SOUND statement. aexp2 = Pitch. Can be any number between 0-255. The larger the number, the lower the pitch. Table 10-1 defines the pitch numbers for the various musical notes ranging from two octaves above middle C to one octave below middle C. aexp3 = Distortion. Can be even numbers between 0-14. Used in creating sound effects. A 10 is used to created a "pure" tone whereas a 12 gives an interesting buzzer sound. A buzzing sound (like engines at a race track) can be produced using two separate SOUND commands with the distortion value (aexp3) alternating between 0 and 1.

A value of 1 is used to force output to the speaker using the specified volume (see aexp4). The rest of the numbers are used for other special effects, noise generation, and experimental use. aexp4 =

Volume control. Can be between 1 and 15. Using a 1 creates a sound barely audible whereas a 15 is loud. A value of 8 is considered normal. If more than 1 sound statement is being used, the total volume should not exceed 32. This will create an unpleasant "clipped" tone.

Sounds and Garne Controllers

Sound.s and Garne Controllers

Using the note values in Table 10-1, the following example demonstrates how to write a program that will "play" the C scale.

TABLE 10.1. TABLE OF PITCH VALUES FOR THE MUSICAL

NOTES

HIGH

NOTES

MIDDLE C

LOW NOTES

A# or Bb

G# or Ab

F# or Gb

D# or E

C# or Db

A# or B

G# or Ab

F# or Gb

D# or El'

C# or Db

A# or Bb

G# or Ab

F# Gb

D# or El'

C# or Db

10 READ A

20 IF A=25.6 THEN END

30 SOUND 0, A, 12, 12

40 FÜR W=1 TO 400 NEXT W

50 PRINT A

60 GOTO 10

70 9'40

'30 DATA 29, 31,

.91 , 96 , 108, 121

45, 47, 53.. GO, 72, 81

90 DATA 128, 144, le2, 132, 193, 217, 247, 25(::

Figure 10-1. Musical Scale Program

102

108

114

121

128

136

144

153

162

173

182

193

204

217

230

243

Note that the DATA statement in line 80 ends with a 256, which is outside of the designated range. The 256 is used as an end-of-data marker.

GAME

Figure 10-2 is an illustration of the three controllers used with the Atari Per

CONTROLLER sonal Computers. The controllers cän be attached directly to the Atari Per- sonal Computer or to external mechanical devices so that outside events can be

FUNCTIONS fed directly to the computer for processing and control purposes.

PADDLE

PTRIG

STICK

Figure 10-2. Garne Controllers

Format:

PADDLE(aexp)

Example: PRINT PADDLE(3)

This function returns the status of a particular numbered controller. The paddle controllers are numbered 0-7 from left to right. This function can be used with other functions or commands to "cause" further actions like sound, graphics controls, etc. For example, the statement

IF PADDLE(3) = 14 THEN PRINT

"PADDLE ACTIVE."

Note that the PADDLE function returns a number between 1 and 228, with the number increasing in size as the knob on the controller is rotated counterclockwise (turned to the left).

Format:

PTRIG(aexp)

Example:

100 IF PTRIG(4)=0 THEN PRINT "MISSILES FIRED!"

The PTRIG function returns a status of 0 if the trigger button of the designated controller is pressed. Otherwise, it returns a value of 1. The aexp must be a number between 0 and 7 as it designates the controller.

Format:

STICK(aexp)

Example:

100 PRINT STICK(3)

This function works exactly the same way as the PADDLE command, but can be used with the joystick controller. The joystick controllers are numbered from

0-3 from len to right.

Controller 1 = STICK(0)

Controller 2 = STICK(1)

Controller 3 = STICK(2)

Controller 4 = STICK(3)

Figure 10-3 shows the numbers that will be returned when the joystick controller is moved in any direction.

Sounds and Game Controllers 59

14 -

11

7

STRIG

13

Figure 10-3. Joystick Controller Movement

Format:

STRIG(aexp)

Example:

100 IF STRIG(3)= 0 THEN PRINT "FIRE TORPEDO"

The STRIG function works the same way as the PTRIG function. lt can be used with both the joystick and keyboard controllers.

Sounds und Garne Controllers

ADVANCED PROGRAMMING

TECHNIQUES

This section includes hints on increasing programming efficiency, conserving memory, and combining machine language programs with Atari BASIC programs. This section does not include an instruction set for the 6502 microprocessor chip nor does it give instructions on programming in machine language. An additional purchase of the Atari Assembler Editor cartridge* and a careful study of Atari's Assembler Editor Manual are strongly recommended.

MEMORY

CONSERVATION

These hints give ways of conserving memory. Some of these methods make programs less readable and harder to modify, but there are cases where this is necessary due to memory limitations.

1. In many small computers, eliminating blank spaces between words and characters as they are typed into the keyboard will save memory. This is not true of the ATARI Personal Computer System, which removes extra spaces.

Statements are always displayed the same regardless of how many spaces were used on program entry. Spaces should be used (just as in typing on a conventional typewriter) between successive keywords and between keywords and variable names. Here is an example:

10 IF A = 5 THEN PRINT A

Note the space between IP and A and between THEN and PRINT. In most cases, a statement will be interpreted correctly by the computer even if all spaces are left out, but this is not always true. Use conventional spacing.

Each new line number represents the beginning of what is called a new

"logical line". Each logical line takes 6 bytes of "overhead", whether it is used to full capacity or not. Adding an additional BASIC statement by using a colon (:) to separate each pair of statements on the same line takes only 3 bytes.

*Available late 1980.

Advanced Programming Teclmiques

If you need to save memory, avoid programs like this:

19 X=Y+1

29 Y=Y+1

39 2=X+Y

40 PRINT Z

59 GOTO 50 and consolidate lines like this:

19 X=X+1:7

2.

141:Z=X+Y:PRINT Z:GOTO 19

This consolidation saves 12 bytes.

Variables and constants should be "managed" for savings, too. Each time a constant (4,5,16,3.14159, etc.) is used, it takes 7 bytes. Defining a new variable requires 8 bytes plus the length of the variable name (in characters).

But each time it is used after being defined, it takes only 1 byte, regardless of its length. Thus, if a constant (such as 3.14159) is used more than once or twice in a program, it should be defined as a variable, and the variable name used throughout the program. For example:

19 PI=3.14159

20 PRINT "AREA OF A CIRCLE IS THE RADIUS

SQUARED TIMES ";PI

Literal strings require 2 bytes overhead and 1 byte for each character

(including all spaces) in the string.

String variables take 9 bytes each plus the length of the variable name

(including spaces) plus the space eaten Up by the DIM statement plus the size of the string itself (1 byte per character, including spaces) when it is defined.

Obviously, the use of string variables is very costly in terms of RAM.

6. Definition of a new matrix requires 15 bytes plus the length of the matrix variable name plus the space needed for the DIM statement plus 6 times the size of the matrix (product of the number of rows and the number of columns). Thus, a 25 row by 4 column matrix would require 15 + approximately 3 (for variable name) + approximately 10 (for the DIM statement) + 6 times 100 (the matrix size), or about 630 bytes.

Advanced Programming Techniques

Each character after REM takes one byte of memory. Remarks are helpful to people trying to understand a program, but sometimes it is necessary to remove remark statements to save memory.

Subroutines can save memory because one subroutine and several short calls take less memory than duplicating the code several times. On the other hand, a subroutine that is only called once takes extra bytes for the GOSUB and RETURN statements.

Parentheses take one byte each. Extra parentheses are a good idea in some cases if they make an expression more understandable to the programmer.

However, removing unnecessary parentheses and relying on Operator precedence will same a few bytes.

PROGRAMMING

Machine language is written entirely in binary code. The ATARI Personal Com

IN MACHINE

LANGUAGE

puter contains a 6502 microprocessor and it is possible to call 6502 machine code subroutines from BASIC using the USR function. Short routines may then be entered into a program by hand assembly (if necessary).

Before it returns to BASIC, the assembly language routine must do a pull accumulator (PLA) instruction to remove the number (N) of input arguments off the stack. If this number is not 0, then all of the input arguments must be popped off the stack also using PLA. (See Figure 6-1).

The subroutine should end by placing the low byte of its result in location 212

(decimal), and then return to BASIC using an RTS (Return from Subroutine) instruction. The BASIC interpreter will convert the 2-byte binary number stored in locations 212 and 213 into an integer between 0 and 65535 in floating-point förmat to obtain the value returned by the USR function.

The .ADR function rnay be used to pass data that is stored in arrays or strings to a subroutine in machine language. Use the ADR function to get the address of the array or string, and then use this address as one of the USR input arguments.

The following program, Hexcode Loader, provides the means of entering hexadecimal codes, converting each hexadecimal number to decimal, and storing the decimal number into an array. The array is then executed as an assembly language subroutine. (An array is used to allocate space in memory for the routine.)

Advanced Programming Techniques 63

1. To use this program, first enter it. After entering it, save this program on disk or cassette for future use.

10 GRAPHICS 0:PRINT "HEXCODE LOADER PROG

RAM:PRINT

20 REM STORES DECIMAL EOUNALENTS IN ARR

AY A, OUTPUTS IN PRINTED 'ETA STATEMENT

S' AT

21 REM LINE NUMBER 1500.

30 REM USER TI-EN PLACES CURSOR ON PRINTE

D OUTPUT LINE, HITS "RETURN«, AND ENTERS

31 REM REST OF BASIC PROGRAM INCLUDING U

SR STATEMENT.

°IM A( 50 ) HEU( 5 >

50 REM INRUT,DONUERSION,STORAGE OF DATA.

60 N=0:PRINT "ENTER 1 HEX CODE. IF LAST

ONE IS IN, ENTER TONE'.";

70 INPUT HE:e

80 IF HEX$="00NE" THEN N=999:GOTO 130

90 FÜR I=1 TO LEN(HEX$)

100 IF HEXS(I,I)<="9" THEN N=N*16+UAL(HE e(I,I)):GOTO 120

110 N=N*16+ASC(HEX$(1,I))-ASC("A")+10

120 NEXT I

139 PRINT N:C=C+1

140 A(C)=N

150 IF N<>999 THEN GOTO 60

190 REH PRINT OUT DATA LINE AT 1500

299 GRAPHICS 0:PRINT "1500 DATA";

210 C=0

229 C=C+1

239 IF A(C)=999 THEN PRINT "999" STOP

249 PRINT A(C);",";

252 A(C)=0 •

260 GOTO 220

31e3 PRINT "PUT CORRECT NUMBER OF HEX ET

ES IN LINE 1000. STOP :REM TRAF LINE

999 REM ** EXECUT ION MODULE **

CLR :BYTES=0

1819 TRAF 300 : °IM EE 1::', E( INT( BYTES/6 )+1

1830 FÜR I=1 TO BYTES

1040 READ A:IF A>255 THEN GOTO 1060

1050 POKE ADR(ES)+LA

1060 NEXT I

1070 REM BASIC PART OF USER'S PROGRAM FO

LLOWS

Figure 11-1. Hexcode Loader Input Program

Advanced Programming Teelunanes

Now add the BASIC language part of your program starting at line 1080 including the USR function that calls the machine language subroutine. (See example below.)

Count the total number of hex codes to be entered and enter this number on line 1000 when requested. If another number is already entered, simply replace it.

Run the program and enter the hexadecimal codes of the machine level subroutine pressing

RETURN

after each entry. After the last entry, type

DONE and press

RETURN .

Now the DATA line (1500) displays on the screen. lt will not be entered into the program until the cursor is moved to the

DATA li

RETURN

is pressed.

Add a program line 5 GOTO 1000 to bypass the hexcode loader (or delete the hexcode loader through line 260). Now save the completed program by using CSAVE or SAVE. lt is important to do this before executing the part of the program containing the USR call. A mistake in a machine language routine may cause the system to crash. If the System does hang up, press

SYSTEM RESET

If the system doesn't respond, turn power off and on again, reload the program, and correct it.

Note:

This method only works with relocatable machine language routines.

The follovving tvvo sample programs can each be entered into the Hexcode

Loader program. The first program prints NOTHING IS MOVING while the machine program changes the colors. The second sample program displays a

BASIC graphics design, then changes colors.

1980 GRAPHICS 1+16

1090 FOR 1=1

TO 6

1190 PRINT #6;"notkins is movins!"

1110 PRINT #6;"NOTHING IS MOUING!"

1120 PRINT #6»inoth1ns is ffiovins!"

1130 PRINT #6;"NOTHING IS MOUING!"

1140 NEXT I

1159 Q=USR(AOR(ES)+1)

1160 FOR

I=1 TO 25:NEXT I:GOTO 1150

After entering this program, check that line 1000 reads:

1000 CLR:BYTES = 21

Type RUN

RETURN .

Advanced Progrrunnüng Techniques

Now enter the hexadecimal codes as shown column by column.

BYTES = 21

When completed, type DONE and press

RETURN

Now place the cursor after the last entry (999) on the DATA line and press

RETURN .

Now run the program by typing GOTO has been added, type RUN

RETURN

1000 and pressing

RETURN

or if line 5

Press

BREAK

to stop program and delete line

The second program, which follows, should be entered in place of the

NOTHING IS MOVING program.

Be sure to check the BYTES = count in line 1000. Follow steps 2 through 6.

1080 GRAPHICS 7+16

1090

sm:21_0R

9,9,4

1100 SETCOLOR 1,9,8

1110 SETCOLOR 2,9,4

1120 CR=1

1130 FÜR X=0 TO 159

1140 COLOR INT(CR)

1150 PLOT 80,0

1160 DRAWTO X,95

1170 CR=CR+0.125

1180 IF CR=4 THEN CR=1

1190 NEXT X

1200 X=USR(ADR(E$)+1)

1210 FÜR I=1 TO 15.NEXT I

1220 GOTO 1200

Type RUN

RETURN .

Enter the hexadecimal codes for this program column by column.

BYTES = 21

Advanced

Progrananing Tecludques

When completed, type DONE and press

RETURN

Now place the cursor after the last entry (999) on the DATA line and press

RETURN

Now run the program by typing GOTO 1000 and pressing

RETURN

or add line 5

GOTO 1000 and type RUN

RETURN

Press Cligto stop program and delete line

Figure 11-2 illustrates an assembler subroutine used to rotate colors which might prove useful. lt is included here for the information of the user.

._..,

Address Object

Code

02C4

02C5

02C6

02C7

6000

6001

6003

6006

6009

600C

600D

600F

6011

6014

A200

ACC402

BDC502

9DC402

E002

90F5

8CC602

Assembler Subroutine to Rotate Colors..

Line

No.

0100

0110

0120

0130

0140

0150

0160

0170

0175

0180

0190

0200

0210

0220

0230

0240

0250

0260

Label Mnemonic

LOOP

PLA

LDX

LDY

LDA

STA

INX

CPX

Data

$6000

COLORO

COLOR1,X

COLORO,X

0270

LOOP

0280

0290

BCC

STY

RTS

COLOR3

Routine to rotate COLOR data

From one register to another.

4 colors are rotated. .

Operating System address

COLOR 0 = $02C4

COLOR 1 = $02C5

COLOR 2 = $02C6

COLOR 3 = $02C7

Machine program starting address*

Pop stack (See Chapter 4)

Zero the X register

Save COLOR 0

Increment the X register (add one)

Compare contents of X register vvith 2

Loop if X register contents are less than 2

Save COLOR 0 in COLOR 3

Return from machine level subroutine

Assembler

Prints This

This Portion is Source Information Programmer Enters

Using Atari Assembler Cartridge

Indicates data (source)

* Routine is relocatable

$ Indicates a hexadecimal number

Figure 11-2. Assembler Subroutine To Rotate Colors

Advanced Pryeraniming Teehufanes

NOTES

Notes

APPENDIX A

ALPHABETICAL DIRECTORY

OF BASIC RESERVED WORDS

Note:

The period is mandatory after all abbreviated keywords.

RESERVED

WORD:

ABBREVIATION:

BRIEF SUMMARY

OF BASIC STATEMENT

ABS

ADR

AND

ASC

ATN

BYE

CLOAD

CHR$

CLOG

CLOSE

CLR

COLOR

COM

CONT

COS

CSAVE

CLOA.

CL.

CON.

Function returns absolute value (unsigned) of the variable or expression.

Function returns memory address of a string.

Logical Operator: Expression is true only if both subexpressions joined by

AND

are true.

String function returns the numeric value of a single string character.

Function returns the arctangent of a number or expression in radians or degrees.

Exit from BASIC and return to the resident system or console processor. operating

Loads data from Program Recorder into RAM.

String function returns a single string byte equivalent to a numeric value between 0 and 255 in ATASCII code.

Function returns the base 10 logarithm of an expression.

I/O statement used to close a flle at the conclusion of I/O operations.

The opposite of DIM: Undimensions all strings; matrices.

Chooses color register to be used in color graphics work.

Same as DIM.

Continue. Caus2s a program to restart execution on the next line following use of the

BREAK

key or encounter- ing a

STOP.

Function returns the cosine of the variable or expression

(degrees or radians).

Outputs data from RAM to the Program Recorder for tape storage.

Appendix

A-1

RESERVED

WORD:

DATA

ABBREVIATION:

DEG

DIM

DOS

DRAWTO

END

ENTER

EXP

FOR

FRE

GET

GOSUB

GOTO

GRAPHICS

INPUT

INT

LEN

DE.

DI.

DO.

DR.

GE.

GOS.

GR.

BRIEF SUMMARY

OF BASIC STATEMENT

Part of READ/DATA combination. Used to identify the succeeding items (which must be separated by commas) as individual data items.

Statement

DEG

teils computer to perform trigonometric functions in degrees instead of radians.

(Default in radians.)

Reserves the specified amount of memory for matrix, array, or string. All string variables, arrays, matrices must be dimensioned with a DIM statement.

Reserved word for disk operators. Causes the menu to be displayed. (See DOS Manual.)

Dravvs a straight line between a plotted point and specified point.

Stops program execution; closes files; turns off sounds.

Program may be restarted using CONT. (Note: END may be used more than once in a program.)

I/O command used to store data or programs in untokenized (source) form.

Function returns e (2.7182818) raised to the specified power.

Used with NEXT to establish FOR/NEXT loops. Introduces the range that the loop variable will operate in during the execution of loop.

Function returns the amount of remaining user memory (in bytes).

Used mostly with disk operations to input a single byte of data.

Branch to a subroutine beginning at the specified line number.

Unconditional branch to a specified line number.

Specifies which of the eight graphics modes is to be used. GR.0 may be used to clear screen.

Used to cause conditional branching or to execute another statement on the same line (only if the first expression is true).

Causes computer to ask for input from keyboard. Ex- ecution continues only when

RETURN

key is pressed after inputting data.

Function returns the next lowest whole integer below the specified value. Rounding is always downward, even when number is negative.

String function returns the length of the specified string in bytes or characters (1 byte contains 1 character).

Appendix

RESERVED

WORD:

LET

LIST

LOAD

LOCATE

ABBREVIATION:

LE.

LO.

LOC.

LOG

LPRINT

NEW

NEXT

LP.

NOT

NOTE

OPEN

PADDLE

PEEK

PLOT

POINT

POKE

POP

POSITION

PRINT

NO.

PL.

POK.

POS.

PR. or ?

BRIEF SUMMARY

OF BASIC STATEMENT

Assigns a value to a specific variable name. LET is optional in Atari BASIC, and may be simply omitted.

Display or otherwise output the program list.

Input from disk, etc. into the computer.

Graphics: Stores, in a specified variable, the value that controls a specified graphics point.

Function returns the natural logarithm of a number.

Command to line printer to print the specified message.

Erases all contents of user RAM.

Causes a FOR/NEXT loop to terminate or continue depending on the particular variables or expressions.

All loops are executed at least once.

A "1" is returned only if the expression is NOT true. If it is true, a "0" is returned.

See DOS/FMS Manual...used only in disk operations.

Used with GOTO or GOSUB for branching purposes.

Multiple branches to different line numbers are possible depending on the value of the ON variable or expression.

Opens the specified file for input of output operations.

Logical operator used between two expressions. If either one is true, a "1" is evaluated. A "0" results only if both are false.

Function returns position of the paddle game controller.

Function returns decimal form of contents of specified memory location (RAM or ROM).

Causes a single point to be plotted at the X,Y location specified.

Used with disk operations only.

Insert the specified byte into the specified mernory location. May be used only with RAM. Don't try to POKE

ROM or you'll get an error.

Removes the loop variable from the GOSUB stack. Used when departure from the loop is made in other than normal manner.

Sets the cursor to the specified screen position.

I/O command causes output from the computer to the specified output device.

Appendix A

PTRIG

PUT

RAD

READ

REM

RESTORE

RETURN

RND

RUN

SAVE

SETCOLOR

SGN

SIN

SOUND

SQR

STATUS

STEP

STICK

STRIG

STOP

RESERVED

WORD: ABBREVIATION:

BRIEF SUMMARY

OF BASIC STATEMENT

PU.

REA.

or .

SPACE

RES.

RET.

RU.

SE.

SO.

ST.

STO.

Function returns status of the trigger button on game controllers.

Causes output of a single byte of data from the computer to the specified device.

Specifies that information is in radians rather than degrees when using the trigonometric functions.

Default is to

RAD.

(See

DEG.)

Read the next items in the

DATA

list and assign to specified variables.

Remarks. This statement does nothing, but comments may be printed within the program list for future reference by the programmer. Statements on a line that starts with

REM

are not executed.

Allows

DATA

to be

read

more than once.

RETURN

from subroutine to the statement immediately following the one in which

GOSUB

appeared.

Function returns a random number between 0 and 1, but neyer 1.

Execute the program. Sets normal variables to 0, undims arrays and string.

I/O statement causes data or program to be recorded on disk under filespec proyided with

SAVE.

Store hue and luminance color data in a particular color register.

Function returns + 1 if value is positive, 0 if zero, - 1 if negative.

Function returns trigonometric sine of given value

(DEG

RAD).

Controls register, sound pitch, distortion, and volume of a tone or note.

Function returns the square root of the specified value.

Calls status routine for specified device.

Used with

FOR/NEXT.

Determines quality to be skipped between each pair of loop variable yalues.

Function returns position of stick game controller.

Function returns 1 if stick trigger button not pressed, 0 if pressed.

Causes execution to stop, but does not close files or turn off sounds.

A-4 Appelldia:

RESERVED

WORD: ABBREVIATION:

STR$

THEN

TRAP

USR

VAL

XIO

BRIEF SUMMARY

OF BASIC STATEMENT

Function returns a character string equal to numeric value given. For example:

STR$(65)

returns 65 as a string.

Used with

IF:

If expression is true, the

THEN

statements are executed. If the expression is false, control passes to next line.

Used with

FOR

as in "FOR X = 1 TO 10". Separates the loop range expressions.

Takes control of program in case of an

INPUT

error and directs execution to a specified line number.

Function returns results of a subroutine.

machine-language

Function returns the equivalent numeric value of a string.

General I/O statement used with disk operations (see

DOS/FMS Manual) and in graphics work (Fill).

Appendix

NOTES

Notes

APPENDIX B

ERROR

MESSAGES

ERROR

CODE NO.

ERROR CODE MESSAGE

Memory insufficient to store the statement or the new variable name or to DIM a new string variable.

Value Error: A value expected to be a positive integer is negative, a value expected to be within a specific range is not.

Too Many Variables: A maximum of 128 differed variable names is allowed.

(See Variable Name Limit.)

String Length Error: Attempted to store beyond the DIMensioned string length.

Out of Data Error: READ statement requires more data items than supplied by

DATA statement(s).

Number greater than 32767: Value is not a positive integer or is greater than

32767.

Input Statement Error: Attempted to INPUT a non-numeric value into a numeric variable.

Array or String DIM Error: DIM size is greater than 32767 or an array/martix reference is out of the range of the dimensioned size, or the array/rnatrix or string has been already DIMensioned, or a reference has been made to an undimensioned array or string.

Argument Stack Overflow: There are too many GOSUBs or too large an expression.

Floating Point Overflow/Underflow Error: Attempted to divide by zero or refer to a number larger than 1 x 10 98 or smaller than 1 x 10 - 99 .

Line Not Found: A GOSUB, GOTO, or THEN referenced a non-existent line number.

No Matching FOR Statement: A NEXT was encountered without a previous

FOR, or nested

FOR/NEXT statements do not match properly. (Error is reported at the NEXT statement, not at FOR).

Line Too Long Error: The statement is too complex or too long for BASIC to handle.

GOSUB or FOR Line Deleted:

A NEXT or RETURN statement was encountered and the corresponding FOR or GOSUB has been deleted since the last RUN.

Appendix

8-1

ERROR

CODE NO.

ERROR CODE MESSAGE

RETURN Error:

A RETURN was encountered without a matching GOSUB.

Garbage Error:

Execution of "garhage" (bad RAM bits) was attempted. This error code may indicate a hardware problem, but may also be the result of faulty use of

POKE. Try typing NEW or powering down, then re-enter the program without any POKE commands.

Invalid String Character:

String does not start with a valid character, or string in VAL statement is not a numeric string.

Note:

The following are INPUT/OUTPUT errors that result during the use of disk drives, printers, or other accessory devices. Further information is provided with the auxiliary hardware.

LOAD program Too Long:

Insufficient memory remains to complete LOAD.

Device Number Larger

than 7 or Eclual to 0.

128

129

130

LOAD File Error:

Attempted to LOAD a non-LOAD file.

BREAK

IOCB1

Abort:

User hit

BREAK

key during I/O operation.

already open.

131

132

133

134

135

136

137

138

139

140

141

Nonexistent Device

specified.

IOCB Write Only.

READ command to a write-only device (Printer).

Invalid Command:

The command is invalid for this device.

Device or File not Open:

No OPEN specified for the device.

Bad IOCB Number:

Illegal device number.

IOCB Read Only Error:

WRITE command to a read-only device.

EOF:

End of File read has been reached.

(NOTE:

This message may occur when using cassette files.)

Truncated Record:

Attempt to read a record longer than 256 characters.

Device Timeout.

Device doesn't respond.

Device NAK:

Garbage at serial port or bad disk drive.

Serial bus

input framing error.

Cursor out of range

for particular mode.

142 Serial bus data frame overrun.

lIOCB refers to Input/Output Control Block. The device number is the same as the IOCB number.

Appendix

145

146

147

160

165

166

167

168

169

170

161

162

163

164

171

ERROR

CODE NO. ERROR CODE MESSAGE

143

144

Serial bus data frame checksum error.

Device done error (invalid "done" byte): Attempt to write on a write-protected diskette.

Read after write compare error (disk handler) or bad screen mode handler.

Function not implemented in handler.

Insufficient RAM for operating selected graphics mode.

Drive number error.

Too many OPEN flies (no sector buffer available).

Disk full (no free sectors).

Unrecoverable System data I/O error.

File number mismatch: Links on disk are messed up.

File name error.

POINT data length error.

File locked.

Command invalid (special Operation code).

Directory full (64 flies).

File not found.

POINT invalid.

Appendix

B-3

APPENDIX C

ATASCII

CHARACTER SET

-v

,...%..%? e

4

.e. ee)e4>

(

() ee

1 1 a

.s,

4j;

-o'`'' c°

c°

, v

<s5'

A.e. c

4e3''c'

13 D

eia

123

1:1

8 la

22 16

0111

10 A

Clil

34

35

36

37

38

31

32

33

22

23

24

25

,..."

, zo

e c

0 ei

0

1:1

Space 20

21 !

3 3

#

$

& 26

A ppendix

C-1

(

)

•

' 70

56 V

---

"s-

v clr‚

449÷

.04 cp ei, e e

("ie 47(9 e,...'

58 X

89 59

100

101

102

[

106

107

108

]

_ d e f

113 a b c

109

, 110

111

112

113

114

115

116

117

118

ets*4 e9

09 i3". c›

103

104

105

69 j k

1 g h i

.4% e- v c> ei) e 4 c,°

119

77 e

? (e)

+ e e c, w x

120

121

122

Y z

123

124

7C u v s t o p m n q r

125

126

127

128

129

130

131

132

133

134

Illi

111.

Appendix

C-3

0' c°

135

.%,

,.,

+ c c* e

-%. e-

151 97

(OS' ce

136

152

137

153 99

138 8A

154

139 8B

155

(EOL)

RETURN

140

156

9C t

141 8D

157 9D illr

142

158 9E

143

159 ih

144

160

145 91

161

146

162 A2

147 93

163

148

164 A4

149 95

165 A5

150 96

166

C-4

Appendix

177

178

179

180

181

182

' c°

167 v

..4

■

4 ,c

7 ce

,,.e

168

169

170

171

172

173

174

175

176

,e,

.c ,c

, c„.... e)'

4

183 B7

c

Z9+

4 4 c

199

c

, e e

4

7 44+

c,

ei'

$ c9

4, i,

4

›,c,

•j"(9 e•''

215

184

200

216

185

201

. C9

217

186

187

202

203

218

219

DA bB

188

204 CC

220

221 DD

189

205

190 BE

206 CE

222

191 BF

207 CF

223

224 BO

192

208 DO

193 Cl

209

225

194

210 D2

226

195 C3

211 D3

227

228 E4

196

212 D4

229 E5

197 C5

213 D5

230 E6

198

214 D6

Appendix

C-5

235

236

237

238

239 c›

0 e

,...d•'- er4 e

+ e;9 04 e,

°c

231 E7 240

232 241 E8

233

234 EA

242

243

244

245

246

247

248 eff>9

, c5)

,i4

-e

249

250

FB v ce

‘‘,

251

252

253

254

255

(Bu zzer)

(Delete character)

II,.

(Insert character)

See Appendix H for a user program that performs decimal/hexadecimal conversion.

Notes:

1. ATASCII stands for "ATARI ASCII". Letters and some of the special characters are different. numbers have the same values as those in ASCII, but

Except as shown, characters from 128-255 are reverse colors of 1 to 127.

Add 32 to upper case code to get lower case code for same letter.

To get ATASCH code, teil computer (direct mode) to PRINT ASC (" character, or number of code. Must use the quotes!

") Fill blank with letter,

On pages C-1 and C-3, the normal display keycaps are shown as white Symbols on a black background; on pages C-4 and C-6 inverse keycap symbols are shown as black on a white background.

C-6

Appendix

APPENDIX D

ATARI 400/800

MEMORY MAP

Decimal

ADDRESS

Hexadecimal

65535

57344

57343

55296

55295

53248

53247

49152

49151

40960

40959

32768

32767

FFFF

E000

DFFF

D800

D7FF

D000

CFFF

C000

BFFF

A000

9FFF

8000

7FFF

31755

10880

10879

9856

9855

4864

7CIF

2A80

2A7F

2680

267F

1300

OPERATING SYSTEM ROM

FLOATING POINT ROM

HARDWARE REGISTERS

NOT USED

CARTRIDGE SLOT A

(may be RAM if no A or B cartridge)

CARTRIDGE SLOT B

(may be

RAM if no B cartridge)

RAMTOP (MSB)

(7FFF if 32K system)

DISPLAY DATA (size varies)

DISPLAY LIST (size varies)

« i OS MEMTOP

FREE RAM

(size varies)

BASIC MEMTOP

BASIC program, buffers, tables, run-time stack.

(2A80 if DOS, may vary)

OS MEMLO}

4---

BASIC LOMEM1

DISK OPERATING SYSTEM (2A7F-700)

DISK I/O BUFFERS (current DOS)

DISK OPERATING SYSTEM RAM (current DOS)

Appendix

D-1

..---,\

959

832

831

512

511

256

255

212

211

210

209

208

207

203

202

176

128

127

4863

1792

1791

1536

1535

1406

1405

1152

1151

1021

1020

1000

999

960

Decimal

ADDRESS

Hexadecimal

12FF

700

6FF

600

5FF

5;7E

57D

480

47F

3FD

3FC

3E8

3E7

3C0

3BF

340

33F

200

1FF

100

CONTENTS

FILE MANAGEMENT SYSTEM RAM (current DOS)

F REE RAM

FLOATING POINT (used by BASIC)

BASIC CARTRIDGE

1 OPERATING SYSTEM RAM (47F

200)

CASSETTE BUFFER

R ESERVED

PRINTER BUFFER i IOCB's

1 MISCELLANEOUS OS VARIABLES

HARDWARE STACK

PAGE ZERO

FLOATING POINT (used by BASIC)

BASIC or CARTRIDGE PROGRAM

FREE BASIC RAM

FREE BASIC AND ASSEMBLER RAM

FREE ASSEMBLER RAM

ASSEMBLER ZERO PAGE

BASIC

ZERO PAGE

OPERATING SYSTEM RAM

As the addresses for the top of RAM, OS, and BASIC and the ends of OS and BASIC vary according to the amount of memory, these addresses are indicated by pointers. The pointer addresses for each are defined in Appendix I.

D-2

Appendix

,------\

APPENDIX E

DERIVED

FUNCTIONS

Derived Functions

Secant

Cosecant

Inverse Sine

Inverse Cosine

Inverse Secant

Inverse Cosecant

Inverse Cotangent

Hyperbolic Sine

Hyperbolic Cosine

Hyperbolic Tangent

Hyperbolic Secant

Hyperbolic Cosecant

Hyperbolic Cotangent

Inverse Hyperbolic Sine

Inverse Hyperbolic Cosine

Inverse Hyperbolic Tangent

Inverse Hyperbolic Secant

Inverse Hyperbolic Cosecant

Inverse Hyperbolic Cotangent

Derived Functions in Terms of Atari Functions

SEC(X)=1/COS(X)

CSC(X)=1/SIN(X)

ARCSIN(X)= ATN(X/SQR(-X*X+ 1))

ARCCOS(X) = - ATN(X/SQR( - X*X +1) + CONSTANT

ARSEC(X)=ATN(SQR(X*X-1))+(SGN(X-1)*CONSTANT

ARCCSC(X)=ATN(1/SQR(X*X-1))+(SGN(X-1)*CONSTANT

ARCCOT(X)= ATN(X)+ CONSTANT

SINH(X)= (EXP(X)-EXP(-X))12

COSH(X)= (EXP(X)+EXP(-X))/2

TANH(X)=-EXP(-X)/(EXP(X)+EXP(-X))*2 +1

SECH(X)=2/(EXP(X)+EXP(-X))

CSCH(X)=2/(EXP(X)-EXP(-X))

COTH(X)=EXP(-X)/(EXP(X)-EXP(-X))*2 +1

ARCSINH(X)=LOG(X+SQR(X*X + 1))

ARCCOSH(X)+LOG(X+ SQR(X*X-1))

ARCTANH(X)=LOG((1 + X)/(1-X))/2

ARCSECH(X)=LOG((SQR(-X*X+ 1)+1)/X)

ARCCSCH(X)= LOG((SGN(X)*SQR(X*X + 1)+1)/X)

ARCCOTH(X)=LOG((X+1)/(X-1))/2

Notes:

If in RAD (default) mode, constant = 1.57079633

If in DEG mode, constant = 90.

In this chart, the variable X in parentheses represents the value or expression to be evaluated by the derived function. Obviously, any variable name is permissible, as long as it represents the number or expression to be evaluated.

Apperzdix

E-1

NOTES

Notes

APPENDIX F

PRINTED VERSIONS

OF CONTROL CHARACTERS

The cursor and screen control characters can be placed In a string in a program or used as a Direct mode statement by pressing- the

CM

key before entering the character from the keyboard. This causes the special symbols which are shown below to be displayed. (Refer to Section 1 -

Key.)

SEE THIS

PRESS PRESS

PRESS

III

11111

ei

OR

Cli

1111

DEUTE

SACK

an

PRESS AND

HOLD

PRESS

GED

la

1313

GED

133

CID

CLEAR

III

113 al

11{11

13E3 az an

0 LE E

BAC

iNSERI

DEL

BACK S

133

NSER,

1312

.. s *

111111

EDA:

GED

la

Appendix

F-1

NOTES

Notes

APPENDIX G

GLOSSARY

Alphanumeric:

Array:

ATASCII:

BASIC:

Binary:

Bit:

Branch:

Bug:

Byte:

Central Processing

Uni t (CPU):

Code:

Command:

The alphabetic letters A-Z, the numbers 0-9, and some symbols. (No punctuation marks or graphics symbols).

A list of numerical values stored in a series of memory locations preceded by a DIM statement. May be referred to by use of an array variable, and its individual elements are referred to by subscripted variable names.

Stands für Atari American Standard Code für Information Inter- change.

High level programming language. Acronym für Beginner's All- purpose Symbolic Intruction Code. BASIC is always written using all capital letters. Developed by Mssrs. Kemeny and Kurtz at Dartmouth

College in 1963.

A number System using the base two. Thus the only possible digits are 0 and 1, which may be used in a computer to represent true and false, on and off, etc.

Short for Binary

Digit.

A bit can be thought of as representing true or false, whether a circuit is on or off, or any other type of twopossibility concept. A bit is the smallest unit of data with which a computer can work.

Atari BASIC executes a program in order of line numbers. This execution sequence can be altered by the programrner, and the program can be told to skip over a certain number of lines or return to a line earlier in the program. This contrived change in execution sequence is called "branching".

A mistake or error usually in the program or "software".

Usually eight bits (enough to represent the decimal number 255 or

11111111 in binary notation). A byte of data can be used to represent an ATASCII character or a number in the range of 0 to 255.

In microcomputers such as the Atari systems, these are also called microprocessors or MPU. At one time, the CPU was that portion of any computer that controlled the rnemory and peripherals. Now the

CPU or MPU is usually found on a single integrated circuit or "chip"

(in Atari's case a 6502 microprocessor chip).

Instructions written in a language understood by a computer.

An instruction to the computer that is executed immediately. A good example is the BASIC command RUN. (See

Statement.)

Appendix

DOS:

Editing:

Execute:

Expression:

Format:

Hard Copy:

Appendix

Computer:

Concatenation:

Control Characters:

CRT:

Cursor:

Data:

Debug:

Default:

Digital:

Diskette:

Any device that can receive and then follow instructions to manipulate information. Both the instructions and the information may be varied from moment to moment. The distinction between a computer and a programmable calculator lies in the computer's ability to manipulate text as well as numbers. Most calculators can only handle numbers.

The process of joining two or more strings together to form one longer string.

Characters produced by holding down the key labeled • while simultaneously pressing another key.

Abbreviation for "cathrode ray tube" (the tube used in a TV set). In practice, this is often used to describe the television receiver used to display computer output. Also called a "monitor".

A square displayed on the TV monitor that shows where the next typed character will be displayed.

Information of any kind.

The process of locating and correcting mistakes and errors in a program.

A mode or condition "assumed" by the computer until it is told to do something else. For example, it will "default" to screen and keyboard unless told to use other devices.

Information that can be represented by a collection of bits. Virtually all modern computers, especially microcomputers, use the digital approach.

A small disk. A record/playback medium like tape, but made in the shape of a flat disk that is placed inside a stiff envelope for protection.

The advantage of the disk over cassette or other tape for memory storage is that access to any part of the disk is virtually immediate.

The Atari 800 Personal Computer System can control up to 4 diskette drive peripherals simultaneously. In this manual, disk and diskette are used interchangeably.

Abbreviation for "disk operating system". The software or programs which facilitate use of a disk-drive system. DOS is pronounced either "dee oh ess" or "doss".

Making corrections or changes in a program or data.

To do what a command or program specifies. To RUN a program or portion thereof.

A combination of variables, numbers, and operators (like +‚ -, etc.) that can be evaluated to a single quantity. The quantity may be a string or a number.

To specify the form in which something is to appear.

Printed output as opposed to temporary TV monitor display.

Hardware:

Increment:

Initialize:

Input:

Interactive:

Interface:

IOCB

I/O:

Keyword:

Language:

Memory:

Menu:

Microcomputer:

Monitor:

Null String:

OS:

Output:

Parallel:

Peripheral:

The physical apparatus and electronics that make up a computer.

Increase in value (usually) by adding one. Used a lot for counting (as in counting the number of repetitions through a loop).

Set to an initial or starting value. In Atari BASIC, all non-array variables are initialized to zero when the command RUN is given. Array and string elements are not initialized.

Information transfer to the computer. Output is information transfer away from the computer. In this manual, input and output are always in relation to the computer.

A System that responds cluickly to the user, usually within a second or two. All personal computer Systems are interactive.

The electronics used to allow two devices to communicate.

Input/Output Control Block. A block of data in RAM that tells the

Operating System the information lt needs to know for an I/O Operation.

Short for input/output, devices include the keyboard, TV monitor, program recorder, printer, and disk drives.

Stands for "kilo" meaning "times 1000". Thus 1 KByte is (approximately) 1000 bytes. (Actually 1024 bytes.) Also, the device type code for the Keyboard.

A word that has meaning as an instruction or command in a computer language, and thus must not be used as a variable name or at the beginning of a variable name.

A set of conventions specifying how to tell a computer what to do.

The part of a computer (usually RAM or ROM) that stores data or information.

A list of options from which the user may choose.

A computer based on a microprocessor chip; in Atari's case, the6502.

The television receiver used to display computer output.

A string consisting of no characters whatever.

Abbreviation for Operating System. This is actually a collection of programs to aid the user in controlling the computer. Pronounced

"oh ess".

See I/O.

Two or more things happening simultaneously. A parallel interface, for example, controls a number of distinct electrical signals at the same time. Opposite of serial.

An I/O device. See I/O.

Appendix G-3

Pixel:

Precedence:

Program:

Prompt:

RAM:

Random Number

Generat on

Reserved Word:

ROM:

Save:

Screen:

Serial:

Software:

Special Character:

Statement:

String:

Subroutine:

Variable:

Window:

G-4

Appendix

Picture Element. One point on the screen display. Size depends on graphics mode being used.

Rules that determine the priority in which operations are conducted, especially with regard to the arithmetical/logical operators.

A sequence of instructions that describes a process. A program must be in the language that the particular computer can understand.

A symbol that appears on the monitor screen that indicates the computer is ready to accept keyboard input. In Atari BASIC, this takes the form of the word "READY". A "?" is also used to prompt a user to enter (input) information or take other appropriate action.

Random Access Memory. The main memory in most computers.

RAM is used to store both programs and data.

May be hardware (as is Atari's) or a program that provides a number whose value is difficult to predict. Used primarily for decisionmaking in game programs, etc.

See Keyword.

Read Only Memory. In this type of solid-state electronic memory, information is stored by the manufacturer and it cannot be changed by the user. Programs such as the BASIC interpreter and other car- tridges used with the Atari systems use ROM.

To copy a program or data into some location other than RAM (for example, diskette or tape).

The TV screen. In Atari BASIC, a particular I/O device codes "S:"

The opposite of parallel. Things happening only one at a time in sequence. Example: A serial interface.

As opposed to Hardware. Refers to programs and data.

A character that can be displayed by a computer but is neither a letter

nor a numeral. The Atari graphics symbols are special characters.

So are punctuation marks, etc.

An instruction to the

computer.

See also Command. While all commands may be considered statements, all statements are certainly not commands. A statement contains a line number (deferred mode), a keyword, the value to be operated on, and the

RETURN command.

A sequence of letters, numerals, and other characters. May be stored in a string variable. The string variable's name must end with a $.

A part of a

program that

can be executed by a special statement

(GOSUB) in BASIC: This effectively gives a

single statement

the power of a whole program. The subroutine is a very powerful construct.

A variable may be thought of as a box in which a value may be stored. Such values are typically numbers and strings.

A portion of the TV display devoted to a specific purpose such as for graphics or text.

-----\

APPENDIX H

USER

PROGRAMS

CHECKBOOK

BALANCER

This appendix contains programs and routines that demonstrate the diverse capabilities of the Atari Personal Computer System. Included in this appendix is a Decimal/Hexadecimal program for those users who write programs that reeire this type of conversion.

This is one of the "traditional" programs that every beginning computerist writes. lt allows entry of outstanding checks and uncredited deposits as well as cleared checks and credited deposits.

19 DIM A$(32),ISGe(40),MSG1$(30),MSG2$(3

0),MSG3$(30),MSG4$(39),MSG5$(30),MSG6$(3

0.) •

20 OUTSTAND=9 •

39 GRAPHICS 0:? ,? "

CHECKBOOK BALAN

CER".:?

? "You 4.121 make correctione at an me b9 enterine a neeative dollar value.

MSG14".."OLD CHECK -- STILL OUTSTANDING

69 MSG2$="OLD DEPOSIT -- NOT CREDITED

70 MSG3$="OLD CHECK -- JUST CLEARED

89 MSG4$="OLD DEPOSIT JUST CREDITED

. •

90 MSG5$="NEW CHECK UR SERVICE CHARGE)

190 MSGES="NEW DEPOSIT (OR INTEREST)

159 TRAF' . 150:? "Enter beeinnine balance from 9our.• . checkboökni:INPUT YOURBAL

160

TRAF' 160.? "Enter beeinnine balance frce

9our i.... __n BANKBAL

165 TRAP 40000

170 GOTO 190

189 CLOSE #1:? "PRINTER IS NOT OPERATION

185 ? "PLEASE CHECK CONNECTORS."

190 PERM=0

202 '? "Would

90U like a permanent record on the printer"J:INPUT AS

219 IF LEN(AS)=0 THEN 200

Appendix

H-1

Appendix

220 IF A$(1,1)="N"

THEN

400

230 IF A$( 1,1)<>"Y" THEN 200

240 TRAP 180

250 LPRINT

:REM

TEST PRINTER

260

PERM=1

290 LPRINT "YOUR BEGINNING BALANCE 12 $"

;YOURBAL

290 LPRINT

"BANK

STATEMENT BEGINNING EL

ANCE

$";BANKEAL , LPRINT •

400 TRAP 400:? :? "ChooP onP of tkP fol lowire , "

410 •

"(1)

415 ? "(2)";MSG2$

420 • (3)

;M3G3$

425 ? "(4)

";MSG4$

43) ? "(5)

";MSG5$

435 ? "(6)

499 ?

500 INPUT

505 TRAF' 48000

N<1

N>7

THEN

400

510 ON N GOSUB 1000,2000,3000,4000,5000,

6090,7000

520 MSG$="NEW

CHECKBOOK

BALANCE IS

":AMOUNT=YOURBAL:GOSUB

8000

539

MSG$="NEW BANK STATEMENT BALANCE

":AMOUNT=BANKBAL:GOSUB

8000

549

MSG$="OUTSTANDING

CHECKS-DEPOSITS=

".AMOUNT=OUTSTAND ,

GOSUB 9000

545 IF PERM THEN LPRINT

559 GOTO 400

1000

REM

OLD

CHECK -- STILL

OUTSTANDING

1010 MSG$=MSG1$ ,

GOSUB

8100

1920

1030

OUTSTAND=OUTSTAND+AMOUNT

RETURN

2000 REM OLD DEPOGIT -- STILL NOT CREDIT

2010

2020

M3G$=MSG2$:GOSUB

9100

OUTSTAND=OUTSTAND-AMOUNT

2030 RETURN

3000

3010

3020

3930

4090

REM

OLD CHECK -- JUST CLEARED

MSG$=MSG3$:GOSUB

8100

BANKBAL=BANKBAL-AMOUNT

RETURN

REM OLD DEPOSIT

JUST CREDITED

4010 MSG$=MSG4$:GOSUB

8100

4020

4030

BANKBAL=BANKBAL+AMOUNT

RETURN

5000

REM NEW

CHECK (OR

SERUICE

CHARGE) -

- JUST

CLEARED

5010 MSG$=MSG5$:GOSUB 9100

5920 YOURBAL=YOURBAL-AMOUNT

5030 ? "IS NEW CHECK STILL OUTSTANDING";

:INPUT A$

5040 IF LEN(A$)=0

5050 IF

5055

5857 IF

THEN 5930

A$(1,1)<>"N" ThEN 5060

BANKBAL=BANKBAL-AMOUNT

PERM THEN LPRINT "CHECK HAS CLEA

RED."

5858

RETURN

5860 IF A$(1,1)<>"Y" TEEN 5030

5970

OUTSTAND=OUTSTANDAMOUNT

5075 IF

PERWTHEN LPRINT "CHECK IS STILL

OUTSTANDING."

5980 RETURN

6890

REM

NEW DEPOSIT

ZOR INTEREST) -- JU

ST CREDITED

6010

MSGS=18G6$:GaSU8 8109

6020 YOURBAL=YOURBAL+AMOUNT

6930 ? "HAS YOUR NEW DEPOSIT BEEN

CREDIT

ED"i:INPUT A$

6040 IF LEN(A$)=0 THEN 6030

6050 IF

A$(1,1)(>"Y" THEN 6060

6952 BANKBAL=BANKBALAMOUNT

6053 IF

PERM THEN LPRINT "DEPOSIT HAS BE

EN CREDITED."

6855

RETURN

6960 IF

6870

A$(1,1)<>"N" TI-EN

6030

OUTSTAND=OUTSTANO-AMOUNT

6075 IF

PERM THEN LPRINT "DEPOSIT HAS NO

T BEEN CREDITED."

6880

RETURN

7990 REM DONE

7910 ? "

BANK'S BALANCE MINUS (OUTSTANDIN

G CHECKS-DEPOSITS) SHOULD NOW EQUAL

YOURCHECKBOOK BALANCE."

7920

DIF=YOURBAL-(BANKBAL-OUTSTAND)

7030 IF DIF<•0

7035 ? "IS

THEN 7040

$";BANKBAL;" THE ENDING BALAN

CE ON YOUR BANK STATEMENT"J:INPUT A$

7936 IF LEN(A$)=0 THEN 7035

7037 IF

A$(1,1)="Y" THEN ? "CONGRATULATI

ONS: YOUR CHECKBOOK

BALANCES!":ENO

7938 GOTO 7960

7040 IF

MFA THEN ? "YOUR CHECKBOOK TOT

IS $";DIF;"

OVER YOUR BANK '5 TOTAL. n

:TO 7060

7950 ? "

YOUR CI-ECKBOOK TOTAL IS $';-DIFJ

" INDER YOUR BANK'S TOTAL."

7960 ? "WOULD

YOU LIKE TO MAKE CORRECTIO

NS?"

7070 ? "REMEMBER, YOU CAN ENTER A NEGATI

DOLLAR UALUE TO MAKE A CORRECT ION.

Appendix

H-3

11-4

Appendix

7080 "ENTER Y OR N";:INPUT A$

7090 IF LEN(A$>=0 THEN Et)

7180 IF A$(1,1)="Y" THEN RETURN

7110 EMD

7999 REM MSG PRINTING ROUTINE

8000 MSG.;" $";AMOUNT

8018 IF PERM=1 THEN LPRINT MSG;" $";AMO

UNT

8020 RETURN

8100 REM MSG PRINT t INPUT ROUTINE

8110 TRAP 8110:1> "ENTER AMOUNT FÜR ";MSG

INPUT AMOUNT

8120 TRIP 40000

8130 IF PERM=1 THEN LPRINT MSGe.;" $";AMO

UNT

8140 RETURN

BUBBLE SORT

This program uses the string comparison operator "<=" that orders strings according to the ATASCII values of the various characters. Since Atari BASIC does not have arrays of strings, all the strings used in this program are actually substrings of one large string. A bubble sort, though relatively slow if there are a lot of items to be stored, is easy to write, fairly short, and simpler to understand than more complex sorts.

10 DIM BEI.)

20 GRAPHICS 9.? .? "

STR I NG SO

RT".?

39 TRAP. 30.? .? "Enter maximum strin9 le n9th";INPUT SLEN.SLEN1=SLEN-1

35 IF.SLEN<1 OR INT(SLENX>SLEN THEN ?'"

PLEASE ENTER A POSITIVE INTEGER > 0.".G0

T030

40 TRAF' 40:

"Enter maximuM number of entries.".

41 ? "(EntrieS which are skorter Ulan th e maximum will be padded with blanks.)

42 INPUT BNTRIES

45 IF ENTRIES<2 OR INT(ENTRIESX>ENTRIES

THEN ? "PLEASE ENTER A POSITIVE INTEGER

> 1.".GOTO 40

47 TRAP 40000

•

50 DIM AESLEN*ENTRIES),TEMPESLEN)

"Enter.strin9s one at a time."

79 ? "Enter emPt9 trin' w-en done (just hitRETURN)."

75 ? .? "PLEASE. STAND BY WHILE

TU STRIN

GS ARE BEING CLEARED..";

80 FÜR I=1 TO SLEMENTRIES.AVI,I)=" ".N

EXT I

85 • .?

90 I=1

- •

190 FÜR J=1 TO ENTRIES

119 ? "it";j;" ";.INPUT TEMPS •

120 IF LEN(TEMPS)=0 THEN ENTRIES=j-1.GOT

0 190

130' AVIA+SLEN1)=TEMP$

140 I=I+SLEN

159 NEXT J

199 ? .? .? "PLEASE STAND BY WHILE THE S

TRINGS ARE BEING SORTED...";

200

174

0SUB 1000:REM CALL SORT ROUTINE

292 ? .?

205 1=1

210 FÜR K=1 TO ENTRIES

220 ? "*";K;" "X I.

225 I=I+SLEN

230 NEXT K

240 TRAF' 390.? .? "WOULD YOU LIKE A PRIM

Appendix H-5

Appendix

TED

COPYlii:INPUT

250 IF B$(1,1)="i"

THEN 400

300 ENO

400 I=1:LPRINT :FOR K=1 TO ENTRIES

420 LPRINT "*";K;" "Al$(.1,1+SLEN1)

430 I=I+SLEN:NEXT K:ENO

1000 REM STRING BUBBLE SORT ROUTINE

1010 REM INPUT: A$)SLEN,ENTRIES.

1015 REM TEMP$ MUST HAUE A DIMENSION OF

SLEN.

1020 SLEN1=SLEN-1:MAX=SLENUENTRIES-1)+1

1040 FÜR I=1 TO MAX STEP SLEN

1050 DONE=1

1060 FÜR K=1 TO

MAX-I-SLEN1 STEP SLEN

1070 KSLEN1=K+SLEN1:KSLEN=K+SLEN:KSLE4SL

EN1=KSLEN+SLEN1

1080 IF

AVK,KSLEN1)<=e(KSLENKSLENSLEN

I) THEN GOTO 1110

1090 DONE=0

1100 TEMPS=WK,KGLEN1):WK,KSLEN1)=AV

KSLEN,KSLENSLEN1) . AEKSLEN,KSLENSLEN1)=T

EMP$

1110 NEXT K

1120 IF DÜNE THEN RETURN

1130 NEXT I

1140 RETURN

TEXT MODES

This program prints the Atari characters in their default colors for text modes

0, 1, and 2. In entering this program, remember that the clear screen symbol

CHARACTER

"-.1" is printed as " ".

1 DIM A$(1)

1 ")".REM CLEAR SCREEN

19 ?

"GRAPHICS 9, 1, AND 2 (TEXT MODE

20 ? "DEMONSTRATION."

30 ? "DISPLAYS CHARACTER SETS FÜR LACH M

ODE."

60 WAIT=1000.REM SUBROUTINE LINE NUMBER

70 CHBAS=756.REM CHARACTER BASE ADDRESS

BO UPPER=224.REM DEFAULT FÜR CHBAS

90 LOWER=226.REM LOWER CASE LETTERS & GR

APHICS

95 GOSUB WAIT

100 FÜR L=0 TO 2

112 REM USE E. FÜR GRAPHICS 0

115 IF L=0 THEN OPEN #1,8,0,"E.".GOTO 11

116 REM USE 8. FÜR GRAPHICS 1 AND 2

117 OPEN #1,9,0,"S."

118 GRAPHICS L

120 PRINT "GRAPHICS ";L

130 FÜR J=9 TO 7.REM 8 LIMES

140 FÜR 1=0 TO 31:REM 32 CHARSsLINE

150 K=32*J+I

155

REM DON'T DISPLAY "CLEAR SCREEN" OR

"RETURN"

160 IF K=ASC(")") OR K=155 THEN 180

165 IF L=0 THEN PUT #1,ASC(" ").REM ESCA

170 PUT #1,K.REM DISPLAY CHARS

180 NEXT I

190 PRINT - #1;" ".REM EMD OF LINE

200 IF L<>2 OR J<>3 THEN 240

210 REM SCREEN FULL

220 GOSUB WAIT

230 PRINT #1;")".REM CLEAR SCREEN

240 NEXT J

250 GOSUB WAIT

265 PRINT "LOWER CASE AND GRAPHICS"

270 IF L<>0 THEN POKE CHBAS,LOWER.GOSUB

WAIT

275 CLOSE #1

280 NEXT L

300 GRAPHICS 0.END

1000 REM WAIT FÜR "RETURN"

1010 PRINT "HIT RETURN TO CONTINUE";

1020 INPUT AS

1030 RETURN

Appendix

LIGHT SHOW This program demonstrates another aspect of Atari graphics. lt uses graphics mode 7 for high resolution and the PLOT and DRAWTO statements to draw the lines. In line 20, the title will be more effective if it is entered in inverse video

(use the Atari logo key).

19 FÜR $T=1 TO 8:GRAPHIC5 7

15 POKE 752,1

20 ? :? " •

Atari's Special Lieht Show

":SETCOLOP 2,0,0

39 SETCOLOR 1,2*ST,8:COLOR 2

40 FÜR DR=0 TO Si STEP ST

59 PLOT 0,0:DRAWTO 100,DR

60 NEXT OR:FOR N=1 TO 800:NEXT N:NEXT ST

70 FÜR N=1 TO 2000:NEXT WWTO 10

11-8

Appendix

UNITED STATES

This program involves switching colors to set up the stripes. lt uses graphics mode 7 plus 16 so that the display appears as a full-screen. Note the cor-

FLAG respondence of the COLOR staternents with the SETCOLOR statements. For fun and experimentation purposes, add a SOUND statement and use a READ/DATA combination to add "The Star Spangled Banner" after line 470. (Refer to Section

10.)

10 REM DRAW THE UNITED STATES FLAG

29 REM HIGH RESOLUTION 4-COLOR GRAPHICS,

NO TEXT WINDOW

30 GRAPHICS 7+16

40 REM SETCOLOR 0 CORP.ESFONDS TO COLOR 1

SETCOLOR 0,4,4

, RED=1

REM SETCOLOR 1 CORRESFONDS TO COLOR 2

79 SETCOLOR 1,0,14:WHITE=2

90 REM SETCOLOR 2 CORRESPONDS TO COLOR 3

90 BLUE=3:REM DEFAULTS TO BLUE

100 REM DRAW 13 RED 2, WHITE STRIPES

119 C=RED

120 FÜR I=0 TO 12

130 COLOR C

140 REM EACH STRIPE HAS SEUERAL HORIZONT

AL LINES

150 FÜR J=0 TO 6

160 PLOT 0,I*7+J

170 DRAWTO 159,I*7+J

190 NEXT J

190 REM SWITCH COLORS

209 C=C+1;IF C>WHITE THEN C=RED

210 NEXT I

300 REM DRAW BLUE RECTANGLE

310 COLOR BLUE

320 FOR 1=0 TO

330 PLOT 0,I

340 DRAWTO 79 , 1

350 NEXT I

360 REM DRAW 3 ROWS OF WHITE STARS

370 COLOR WHITE

380 K=0 , REM START WITH ROW OF 6 STARS

390 FÜR 1=0 TO 2

395 Y=4+1:!/5

400 FOR J=0 TO 4:REM 5 STARS IN A ROW

410 X=K+5+J14 GOstJB 1000

420 NEXT J

430 IF K(>0 THEN K=0 . GOTO 470

440 REM ADD GTH STAR EUEP7 OTHEF LINE

450 X=5+514:GO3UB 1000

460 K=7

470 NEXT I

500 REM IF KEY HIT THEN STOP

Appendix

H-9

Appendix

510 IF PEEK(764=255 THEN 510

515 REM OPEN TEXT WINDOW WITHOUT CLEARIN

G SCREEN

520 GRAPHICS 7+32

525 REM CHANCE COLORS BACi'

530 SETCOLOR 0 , 4,4 . SETWLCP 1,0,14

550 STOP

1090 REM DRAW 1 STAR CENTERED AT

XJ7

1910 PLOT X-1,Y:DRAWTO X+1,Y

1020 PLOT Y-1 PLOT X,V+1

1930 RETURN

SEAGULL OVER

OCEAN

This program combines graphics and sounds. The sounds are not "pure" sounds, but simulate the roar of the ocean and the gull's "tweet". The graphics symbols used to simulate the gull could not be printed on the line printer. Enter the following characters in line 20.

20 B1RD$ = "

To get these symbols, use

Ein

R, R.

10 DIM 8IRD$(4)

29 BIRD:$=u H

FLAG=1:ROW=10:COL=10

GRAPHICS 1:POKE 756,226:POKE 752,1

50 SETCOLOR 0,0,0:SETCOLOR 1,8,14

69 PRINT #6iu the ocean"

R=INT(RNO(ü)*11)

80 POSITION 17,17

99 FOR T=0 TO 10

100 SOUND 0,T,8,4

119 FOR A=1 TO 50:NEXT A

120 IF RNO(0)>0.8 THEN FOR 0=10 TO 5 STE

P -1 :SOUND 1,0,10,INT(RND(0)*10):NEXT D:

SOUND 1,9,0,0

130 GOSUB 200

149 NEXT T

150 FÜR T=10 TO 0 STEP -1

160 SOUND 0,T,8,4

170 FÜR A=1 TO 50:NEXT A

175 IF RND(0)>0.8 THEN FÜR 0=10 TO 5 STE

P -1 :SOUND 1,0,10,8:NEXT D:SOUND 1,0,0,0

180 FÜR H=1 TO 10:NEXT H

185 GOSUB 200

190 NEXT T

195 GOTO 70

200 GOSUB 300

219 POSITION COL,ROW

220 PRINT #65BIROEFLAG,FLAG+1)

230 FLAG=FLAG-1-2:IF FLAG=5 THEN FLAG=1

240 RETURN

300 IF RND(0)>0.5 THEN RETURN

310 POSITION COL,ROW

320 PRINT

*UI

H

330 A=INT(RNNOA3)-1

340 B=INT(RNE1(0)*3)-1

35e ROW=ROW+A

360 IF ROW=0 THEN ROW=1

379 IF ROW=20 THEN ROW=19

380 COL=COLe

390 IF COL=0 THEN 01=1

400 IF COL>18 THEN COL=18

419 RETURN

Appendix 11-11

VIDEO

GRAFFITTI

This program requires a Joystick Controller für each playert Each joystick has one color associated with it. By maneuvering the joystick, different patterns are created on the screen. Note the use of the STICK and STRIG commands.

1 GRAPHICS 0

2 ? "VIDEO GRAFFITI"

5 REM XY ARRAYS HOLD COORDINATES

6 REM FÜR UP TO 4 PLAYERS' POSITIONS.

7 REM COLR ARRAY HOLDS COLORS.

10 DIM AS( 1 )..X( 3 ), Y( 3 ), ULK 3 )

128 ? "USE JOYSTICKS TO DRAW PICTURES"

129 ? "PRESS BUTTONS TO CHANGE COLORS"

130 ? "INITIAL COLORS."

131 ? "JOYSTICK 1 IS RED"

132 ? "JOYSTICK 2 IS WHITE"

133 ? "JOYSTICK 3 IS BLUE"

134 ? "JOYSTICK 4 IS BLACK (BACKGROUND)"

135 ? "BLACK LOCATION IS INDICATE0 BY A

BRIEFFLASH OF RED."

136 ? "IN GRAPHICS 8, JOYSTICKS 1 AND 3

ARE WHITE AND 4 IS BLUE."

138 PRINT "HOW MANY PLAYERS (1-4)";

139 INPUT As.IF LEN(e)=0 THEN A$="1"

140 JOYMAX=UAL(A$)-1

145 IF JOYMAX<0 OR JOYMAX>=4 THEN 138

147 PRINT "GRAPHICS 3 (4024), 5 (80X48)

150 PRINT "7 (160X96), OR 8 (320X192)";

152 INPUT AS:1F LEN(A$)=0 THEN A$="3"

153 A=UAL(e)

154 IF A=3 THEN XMAX=40.YMAX=24.GOTO 159

155 IF A=5 THEN

)MAX=80:YMAX=48:GOTO

159

156 IF A=7 THEN XMAX=160.YMAX=96.GOTO 15

157 IF A=8 THEN XMAX=320.YMAX=192.GOTO 1

158 GOTO 147.REM A NOT VALID

159 GRAPHICS 11+16'

160 FÜR 1=0 TO

J01

MAX.X(I)=XMAX/2+I.Y(I)

=YMAX/2+I.NEXT IREM START NEAR CENTER 0

F SCREEN

161 IF A<>8 THEN

166

162 FÜR 1=0 TO 2.COLR(I)=1.NEXT I

163 SETCOLOR 1,9,14.REM LT. BLUE

165 GOTO 180

166 FÜR I=0 TO 2.COLR(I)=I+1.NEXT.I

167 SETCOLOR 0,4,6..REM RED

168 SETCOLOR 1,0,14.REM WHITE

180 COLR(3)=0

295 FÜR J=0 TO 3

Appendix

300 FÜR 1 20 TO JOYMAX:REM CHECK jOYSTICK

305 REM CHECK TRIGGER

310 IF STRIGKI) THEN 321

311 1F A<>8 THEN 320

312 COLR(I)=COLR(I)+1;IF COLR(I)=2 THEN

COLR(I)=0:REM 2-COLOR MODE

313 GOTO . 321

320 COLR(I)=COLR(I)+1:IF COLR(I)>=4 THEN

COLR(I)=0:REM 4-COLOR MODE

321 1F J>0 THEN COLOR COLR(I):GOTO 325

322 IF COLR(.1)=0 THEN COLOR 1:GOTO 325

323 COLOR 0:REM BLINK CURRENT SQUARE ON

AND OFF

325 MT X( I ), Y( I )

330 JOYIWSTICK(I):REM RED JOYSTICK

340 1F JOYIN=15 THEN 530:REM NO MOUEMENT

342 COLOR COLR(I).REM MAKE SURE COLOR IS

344 PLOT X(I),Y(I)

350

1F JOYIN>=8 THEN 390

360 X(I)=X(I)+1:REM MOVE RIGHT

365 REM 1F OUT OF RANGE THEN WRAPAROUND

370 1F X(I)>=XMAX THEN X(1)=0

380 GOTO 430

390 IF JOYIN>=12 THEN 430

400 X(I)2X(I)-1:REM MOUE LEFT

410 IF WIXO

THEN X(I)=XMAX-1

430 IF

JoyiN<>5 ANn

JOYIN<>9

ANn

JOYIN<>

13 THEN 470 .

440 Y(I)=Y(I)+1:IF Y(i>>=YMAX THEN Y(1)=

0:REM M31JE DOWN

460 GOTO 500

470 IF JOYIN<>6 ANO JOYIN<>10 ANO JOYIN<

>14 THEN 500

480 *.i7, I . )=-Y( 1 )-1 IF `.« I >:::0 THEN 'A 1 =YMAX

-1 , REM MOVE UP

500 PLOT X(I),Y(I)

530 NEXT 1

535 NEXT J

540 GOTO 295

Appendix

11-13

KEYBOARD

CONTROLLER

This program alters registers on a chip called a PIA. To set these back to the default values in order to do further I/O, hit

SYSTEM RESET or POKE PACTL,60. If this program is to be loaded from disk, use LOAD, not RUN and wait for the busy light on the disk drive to go out. Do not execute the program before this light goes out, otherwise the disk will continue to spin.

1 GRAPHICS 0

5 PRINT :PRINT H KEYBOARD CONTROLLER

DEMO"

10 DIM ROW( 3 ), IS( 13 ), SUTTON$( 1 )

39 GOSUB 6000

49 FÜR CNT=1 TO 4

69 POSITION 2,CNT*245:PRINT "CONTROLLER

# ";CNT;":";

79 NEXT CNT

89 FÜR CNT=1 TO 4:GOSUB 7999:POSITION 19

,CNT+CNT+5:PRINT BUTTON$J:NEXT CNT

120 GOTO 80

6000 REM ** SET UP FÜR CONTROLLERS **

6010 PORTA=54016:PORTB.54017:PACTL=54018

.PBCTL=54019.

6020 POKE PACTL,48:POKE PORTA,255:POKE P

ACTL,52:POKE PORTA,221

6925 POKE PBCTLAS:POKE PORTS,235 , POKE P

BCTL,52:POKE PORT 221

6930 ROW(0)=238:ROW(1)=221:ROW(2)=187:RO

W(3)=119

6940 1$=" 123456789*0#"

6950 RETURN

R FOR BUTTON WHICH HAG EEEN PRESSEO ON C

ONTROLLER CNT (1-4). **

7001 REM

NOTE A 1 WILL BE RETURNED I

F NO CONTROLLER IS CZVECTED. **

7002 REM ** A SPACE WILL SE RETURNFO IF

THE CONTROLLER IS OONNEOTFO EUT NO KEY H

AS BEEN PRESSE°.

7993 PORT=PORTA:IF CNT>2 THEN PORT=PORTS

7995 P=1

7998 PAO=CNT+CNT-2

7910 FÜR J=0 TO 3

7920 POKE PORT,RO(j)

7930 FÜR I=1 TO 10.NEST I

7950 IF PADDLFJPAD+: Y>10 THEN F=j-i-JA-J+2.

GOTO 7090

7060 IF PADDLE(PAC»10 THE P=J+Ji-j4.72.:GO

TO 7090

7070 IF STRIG(CNT-1)=0

P=i4.--1-j+4 . J!

TO 7090

7080 NEXT J

7090 BUTTONS=IVP.P)

7095 RETURN

14 Appendix

TYPE-A-TUNE

This program assigns musical note values to the keys on the top row of the keyboard. Press only one key at a time.

KEY

MSERT

EMEll

MUSICAL VALUE

B

B 1

(or A#)

Ab ( or G#)

F# (or G l'.)

B

l' (or D#)

D1) ( or C#)

10 ['IM CHORD(37),TUNE(12)

29 GRAPHICS 0.7 :?

TYPE--TUNE

PROGRAM"

25 ? :? "PRESS KEYS 1-9,0,<,> TO PRODUCE

NOTES.";

27 ? "RELEASE ONE KEY BEFORE PRESS Ih TH

NEXT."

29 ? "OTHERWISE THERE MAY BE A DELAY. 11

39 FOR X=1 TO 37:READ -A:CHORD<X)=A:NEXT

49 FÜR X=1 TO 12:READ AJUN)=A:NEXT X

50 OPEN #1,4,0,"K"

55 OLDCHR=-1

69 A=PEEK(764) , IF A=255 THEN 60

63 IF A=OLDCHR THEN 100

65 OLDCHR=A

70 FÜR X=1 TO 12 , IF TUNE(.2.14 THEN SOUND

9,CHORD<X),10,9 , GOTn 100

89 NEXT X

100 I=INT(PEEK(53775).'4):IF (I/2)=INT(I/

2) THEN 60

119 POKE 764,255SOUND 0,0,0,0:nLDCHP=-1

:GOTO 60

2g0 DATA 243,230,217,204‘193,182 , 173 , 162

,151144,136,129,121,114,108,102 , 96 , 918

5,91,76,72,68,64,60

210 DATA 57,53,50.47 , 45,42,40,37,35 , 33 , 3

1,29

220 DATA 31,30,26,24,29 , 27,51,53,42 ,50,5

4,55

To play "Mary Had A Little Lamb" press the following keys:

5, 3, 1, 3, 5, 5, 5 3, 3, 3

5, 8, 8 5, 3, 1, 3, 5, 5 5, 5, 3, 3, 5, 3, 1

Appendix

H-15

COMPUTER

BLUES

This program generates random musical notes to "write" some very interesting melodies for the programmed bass.

1 GRAPHICS 0:? .? n

Sn:?

2 PTR=1

3 THNOT=1

5 CHORD=1

COMPUTER BLUE

6 PRINT 'TASS TEMPO (1=FA2T)nj

7. INPUT TEMPO

8 GRAPHIC.2416:GOSUB

002

10 DIM BA3E(3,4

20 DIM LOW(7).

25 DIM LINE(16)

26 DIN JAM(3,7)

30 FOR X=1 TO 3

40 FOR'Y=1 TO 4

50 READ A:BASE(X,Y)=A

GO NEXT Y

70 NEXT X

80 FÜR X=1 TO 3:READ A:LOW(X)=A

90 NI---XT X

95 FÜR X=1 TO lfUEAD A.LINEM)=A.NEXT X

96 FÜR X=1 TO 3

97 FÜR Y=1 TO 7

98 READ A:JAM(X,Y)=A:NEXT Y:NEXT X

100 GOSUB 500

110 T=T+1

115 GOSUB 220

120 GOTO 100

200 REM r-- •r--

HIGH STUFE

205 IF R14D(0)<0.25 THEN RETURN

210 IF RND(0)<0.5 THEN 252

220 NT=NT+1

•

30 IF NT>7 THEN NT=7

242 GOTO 29

250 NT=NT-1

255 IF NT<1 THEN NT=1

260 SOUND 2 , JAM(CHORD,NT),10,NT*2

280 RETURN

500 REM PROCESS BASE STUFE

510 IF BASS=1 THEN 700

520 BDUR=BDUR+1

530 IF BOUn<>TEMPO THEN 535

531 BASS=1:EC2=0

535 SOUND 0,LOW(CHORfl>,10,4

54!.1

• e

•:..___•

BA:37

RETURN

:: cHop3..

700 souNo o,o

710 SOuND 1, 0, 0,

720 BOUR=BD:2+1

Appendix

730 IF BDUR(>1 THEN 200

742 BOUR=0:BA33.9

750 THNOT=THNOT+1

760 IF THNOT<>5 THEN BOO

765 TH40T=1

770 PTR=PTR+1

780 IF PTR=17 THEN PTR=1

790 CHORD=LINE(PTR)

800 RETURN

1000 DATA 162,144,136,144A21,108,192,12

8.. 108,96..91..96

1010 DATA 243,182,162

1020 DATA 1,1,1,1,21,1,1,1,3,2,1,

1030 DATA 60,50,47,42,40,33,29

1040 DATA 60, -A,45,42,40,33,2";

1059 DATA 81,68,64,57,53,45,49

002 PRINT *A:PRINT *A:PRINT *A

2005 PRINT *A;" Computer"

2004 PRINT *A

2010 PRINT *6"

070 RETURN

Blues"

Appendix

H-17

DECIMAL/

HEXADECIMAL

CDNVERSION

PROGRAM

This program can be typed in and used to convert hexadecimal numbers to decimal numbers and vice versa.

10

DIM A$(9),AD$(1)

20 GRAPHICS 0:7 :? " HEX NUMBER CONU

ERSIONS":?

39 7 :7 "Enter 'D' for DEC to HEX conver eion.":? "Enter 'H for HEX to DEC conve rsion.".INPUT A$

40 IF LEN<A$)=0 THEN 30

50 IF A$="H" THEN 300

60 IF e<>"0" THEN 30

98 TRAP 90

100 ? :? "ENTER A DECIMAL NUISER FROM 0

THROUGH 9999999999•"

110 ? "DEC:";:INPUT N

120 IF N<0 OR N>=1E+10 THEN GOTO 100

130 1=9

140 TEMP=N:N=INT(N/16)

150 TEMP=TEMP-N*16

160 IF TEMP(10 THEN WI,I)=STRETEMP>.G

OTO 180

170 W.I,I)=CHRETEMP-10+ASC("A"))

189 IF N<>0 THEN 11-1:GOTO 140

190 ? "HEX: "ie(I,9):?

200 GOTO 110

300 TRAP 309

310 ? .? "ENTER A HEX NUMBER FROM 0 THRO

UGH

FFFFFFFF."

320 ? "HEX:"; :INPUT A$

330 N=9

340 FÜR I=1 TO LEN(A$)

345 ADS=A$(1,1):IF ADE"0" THEN 380

350 IF AVI,IX="9" THEN N=U16+UAL(AD$)

.GOTO 370

355 JF D$< "A" THEN 300

357 IF AD$›"F" THEN 300

360 N=N*16+A3C(AD$)-A3C("A")+10

370 NEXT I

380 ? "DEC: ";N:?

390

GOTO 320

480 END

1148 Appendix

APPENDIX I

MEMORY

LOCATIONS

Note: Many of these locations are of primary interest to expert programmers and are included here as a convenience. The labels given are used by Atari programmers to make programs more readable.

LABEL

DECIMAL HEXADECIMAL

LOCATION LOCATION COMMENTS AND DESCRIPTION

APPMHI

RTCLOK

SOUNDR

14,15

1849,20

82,83

12,13,14

52,53

Highest location used by BASIC (LSB, MSB)

TV frame counter (1/60 sec.) (LSB, NSB, MSB)

Noisy I/O Flag (0= cluiet)

Attract Mode Flag (128 = Attract mode)

Left, Right Margin (Defaults 2, 39) LMARGIN,

RIVIARGIN

ROWCRS

COLCRS

OLDROW

OLDCOL

NEWROW

85,86

90.

91,92

55,56

Current cursor row (graphics window).

Current cursor column (graphics window).

Previous cursor row (graphics window).

Previous cursor column (graphics window).

Data under cursor (graphics window unless mode

0).

Cursor row to which DRAWTO will go.

NEWCOL

RAMTOP

LOMEM

MEMTOP

STOPLN

ERRSAV

PTABW

FRO

97,98

106

128,129

144,145

186,187

195

201

212,213

61,62

80,81

90,91

BA,BB

D4,D5

Cursor column to which DRAWTO goes.

Actual top of memory (number of pages).

BASIC low memory pointer.

BASIC top of memory pointer.

Line number at which STOP or TRAP occurred

(2-byte binary number).

Error number.

Print tab width (defaults to 10)

Low and high bytes of value to be returned to

BASIC from USR function.

Appendix 1-1

LABEL

RADFLG

LPENH

LPENV

TXTROW

TXTCOL

COLORO

COLOR1

COLOR2

COLOR3

COLOR4

MEMTOP

MEMLO

CRSINH

CHACT

CHBAS

ATACHR

FILDAT

DSPFLG

SSFLAG

HATABS

IOCB

CONSOL

* Future product.

DECIMAL HEXADECIMAL

LOCATION

251

564

565

656

657,658

708

709

710

711

712

741,742

234

235

290

291,292

2C4

2C5

2C6

2C7

2C8

2E5,2E6

743,744

752

755

756

763

764

765

766

767

794

832

1664-1791

53279

2E7,2E8

2F0

2F3

2F4

2FB

2FC

2FD

2FE

2FF

31A

340

680-6FE

DO1F

COMMENTS AND DESCRIPTIONS

RAD/DEG flag (0= radians, 6= degrees).

Light Pen* Horizontal value.

Light Pen* Vertical value.

Cursor row (text window)

Cursor column (text window)

Color Register 0

Color Register 1

Color Register 2

Color Register 3

Color Register 4

OS top of available user memory pointer (LSB,

MSB)

OS low memory pointer

Cursor inhibit (0= cursor on, 1 = cursor off)

Character mode register (4 = vertical reflect; 2 — normal; 1= blank)

Character base register (defaults to 224) (224 = upper case, 226 = lower case characters)

Last ATASCII character.

Last, keyboard key pressed; internal code; (255 clears character).

Fill data for graphics Fill (XI0).

Display Flag (1 = display control character).

Start/Stop flag for paging (0= normal listing) Set by

Eal 1

Handler address table (3 bytes/handler)

I/O control blocks (16 bytes/IOCB)

Spare RAM

Console switches (bit 2 = Option; bit 1 = Select; bit

0 = Start. POKE 53279,

0 before reading. 0 = switch pressed.)

1-2

Appendix

LABEL

PORTA

PORTB

PACTL

PB TL

SKCTL

DECIMAL

HEXADECIMAL

LOCATION

54016

54017

54018

D300

D301

D302

54019

53775

D303

D2OF

COMMENTS AND DESCRIPTIONS

P.IA Port A Controller Jack I/O ports.

PIA Port B Initialized to hex 3C.

Port A Control Register (on Program Recorder 52

= ON, 60 = OFF).

Port B control register.

Serial Port confrol register. Bit 2=0 (last key still pressed).

Appendi_r

1-3

NOTES

,----,,\

Notes

INDEX

A

Abbreviations, 4-5

Commands in headings, 4

ABS, 33 adata, 5

ADR, 35,63 aexp, 4 aop, 4

Array, 3-4, 41

ASC, 37

ATASCII, 5, 40, C-1 through C-6

ATN, 34

Audio track of cassette, 23 avar, 4

B

BASIC, 1

Blanks (see Spaces)

Booting DOS, 25

Braces, 4

Brackets, 4

Branching,

Conditional Statements, 19

Unconditional Statements, 17

Brightness (see Luminance)

Bubble Sort Program, H-5

Buzzer, 14

Deferred Mode, F-1

Direct Mode, 14

BYE, 9

C

C-Scale Program, 58

Central Input/Output Subsystem, 23

Character

Assigning Color to, 54

ATASCII, C-1 through C-6

Display at specified locations, 46, 47

Set, internal, 55

Sizes in Text modes, 46

Chaining Programs, 30

Checkbook Balancer Program, H-1 through H-4

CHR$, 58

CIO

(see Central Input/Output Subsystem) 6

CLEAR key, 6 clear Screen,

Deferred mode, 5, 14, 46

Direct mode, 6, 46

CLOAD, 24

CLOG, 33

CLOSE, 27

CLR, 43

Codes,

Device, 23-24

Colons, 3, 61

COLOR, 48

Color

Assigning, 54

Changing, 50

Default, 46, 51

Registers, 50

COM

(see

DINO

Computer Blues Program, H-16 cmdno, 30

Comma, 26, 27

Command Strings, 1

Commands

BYE, 9

CONT, 9

END, 9

LET, 10

LIST, 10

NEW, 10

REM, 10

RUN, 11

STOP, 11

Conservation,

Memory, 61

Constant, 2

CONT, 9

Controllers,

Garne, 59

COS, 34

CSAVE, 24

Cursor, 9

Graphics, 49

Inhibit, 46

D

Decimal/Hexadecimal Conversion Program, H-18

Default colors, 46 disk drive, 24, 29 margins in Mode 0, 46 tab settings, 6

Deferred mode, 5

DEG, 35

Devices, 23-24

Delete line, 13

DIM, 41

Direct mode, 5

Disk Drive

Default number, 24, 29

Requirements

(see ATARI DOS Manual)

Disk file

Modification of BASIC program, 31

Display, split-screen override, 45, 47

Distortion, 57

DOS, 25

DRAWTO, 48

Index 117

E

Editing, screen, 13

Editor, Screen, 24

END, 9 before subroutine, 7

End of file, 14

Error messages, B-1 through B-3

Escape key, 5 with Control Graphics Symbols, F-1

EXP, 33 exp, 5

Exponentiation symbol, 6

Expression, 1

.Arithmetic

(see

aexp)

Logical

String

(see

lexp)

(see

sexp) filename, breakdown, 27 filespec, 5

Usage, 26, 27

Fill (XIO), 54

FOR/NEXT, 15 building arrays and matrices, 42

• vvith STEP, 15 vvithout STEP, 15

FRE, 35

Function, 1

Arithmetic

ABS, 33

• CLOG, 33

EXP, 33

INT, 33

LOG, 34

RND, 34

SGN, 34

SQR, 34

Built-in, 7

Derived, E-1

Library, 33

Special Purpose, 35

ADR, 35

FRE, 35

PEEK, 35

POKE, 35

USR, 36

Trigonometrie, 34

ATN, 34

COS, 34

DEG, 35

RAD, 35

SIN, 35

G

Garne controllers

Keyboard, 59

Joystick, 59

Paddle, 59

Video Graffitti program, H-12 through H-13

Garne controller commands

PADDLE, 59

•

PTRIG, 59 -

STICK, 59

STRIG, 60

GET, 28, 49

GOSUB/RETURN, 16, 21

GOTO, 17 with conditional branching, 17

GRAPHICS, 45

Graphics

Modes, 46-47

Statements, 48

COLOR, 48

DRAWTO, 49

GET, 45

GRAPHICS, 48

LOCATE, 48

PLOT, 49

POSITION, 49

PUT, 49

SETCOLOR, 50

.),(I0 (Fill), 54

Graphics Control Characters, 56

H

Harmony, 57

Hexadecimal

/Decimal Conversion Program, H-18

Hexcode Loader program, 64

I

INPUT, 25

Input/Output Commands, 23

CLOAD, 24

CLOSE, 27

CSA VE, 24

DATA, 28

DOS, 25

ENTER, 25

GET, 28

INPUT, 25

LOAD, 26

LPRINT, 26

NOTE, 26

OPEN, 26

POINT, 28

PRINT, 3, 5, 14, 26

PUT, 28

READ, 28

SAVE, 29

STATUS, 29

XIO, 29

Input/Output Devices

Disk Drives (D:), 24

Keyboard (K:), 23

Line Printer (L:), 23

Program Recorder (C:), 23

RS-232 Interface (R:), 24

Screen Editor (E:), 24

TV Monitor (5:), 24

INT, 33

Internal pointer for DATA, 21

Input/Output Control Block, 23

Inverse Key, 5

Invisible graphics cursor, 48-49

IOCB

(see

Input/Output Control Block) jr Joystick Controller, 59

K

Keyboard (K:), 23

Keyboard Controllers, 59

118

Inder

Keyboard Controller Program, H-14

Keys

Special Function

ATARI, 5

BACK SPACE, 6

BREAK, 6

CAPS/LOWR, 5

CLEAR, 6

DELETE, 6

ESCAPE, 5

INSERT, 6

RETUR.N, 6

SYSTEM RESET, 6

TAB, 6

Editing

CTRL (Control) Key, 13

SHIFT key, 13

Cursor Control, 14

Down arrow, 14

Left arrow, 14

Right arrow, 14

Up arrow, 14

Keywords

BASIC, A-1 through A-5

L

LEN, 38

LET, 2, 3, 10

Letters

Capital (upper case), 3

Lower case, 3, 47 lexp, 4

Light Show Program, H-8

Line

Format, 3

Logical, 2

Numbers,

Physical, 2 lineno, 5

LIST, 10

LOAD, 26

Load program from cassette tape, 24

LOCATE, 48

LOG, 34

Loops

Endless, 17

Nested, 15 lop, 4

LPRINT, 26 before CSAVE, 24

Luminance, 50

M

Mandatory # symbol, 26, 27

Margins

Changing, 36, 46

Default in mode 0, 46

Matrix, 41-42

Variable,

Memory Map, D-1 through D-2

Modes, graphics, 46, 47

Modes, operating

Deferred, 5

Direct, 5

Exectite, 5

Memo Pad, 5, 25

Modes, text, 46

Override split-screen, 47

Multiple commands

(see

Command Strings) mvar, 4

N

NEW, 10

Notations floating point, 39 in manual, 3

0

ON/GOSUB, 20

ON/GOTO, 20

OPEN, 26-28

Operators, 2

Arithmetic, 4, 6

Binary, 6, 7

Logical, 4, 6

RelatiOnal, 7

Unary, 6

Output devices, 23

Oversized programs

(see

Chaining Programs)

P

Paddle Controller, 59

Parentheses,

Usage, 7, 63

PEEK, 35

Peripheral devices

Pitch

Definition, 57

Values, 58

Pixel, 48

Size in modes, 47

PLA, 63

PLOT, 49

POINT, 28

(see

Input/Output Devices)

POKE, 35

POP, 20-21

POSITION, 49

Precedence, operator, 7

PRINT, 3, 5, 14, 26

Printer listing, 10

Program continuation, 11

Programs,

Machine language, 67

User, Appendix H with Hexcode Loader, 65, 66

PUT, 49

Question mark as prompt, 25

Quotation marks, 2

R

RAD, 35

RAM (Random Access Memory), 23

Random Access to disk file, 28

READ, 28

Direct mode, 28

REM, 10

RESTORE, 21

RETURN Key, 6

Return, Abnormal

Rollbver,

Keyboard, 8

RND, 34

(see

POP)

Index

119

RS-232(R:), 24

RTS, 63

RUN, 11

SAVE, 29

Save programs on cassette tape, 24

Screen Display (see TV Monitor)

Screen Editor (E:), 24

Seagull Over Ocean Program, H-11

Semicolon, 28

SETCOLOR, 50-53 sexp, 5

SGN, 34

SIN, 35

SOUND, 57 terminating, 9, 57

Spaces, 61

SQR, 34

Stack, 16

GOSUB, 16

Hardware, 36 loop addresses, 16, 21

POP, 20

Statement,

Program, 15

FOR, 15

GOSUB, 16, 21

GOTO, 17

IF, 18

ON/GOSUB, 20

ON/GOTO, 20

POP, 20

RESTORE, 21

RETURN, 16

STEP, 15

THEN, 18

TO, 15

TRAP, 22

STEP, 15

STOP, 11

String

Comparison, 40

Concatenation, 39

Dimensioning, 37

Functions

ASC, 37

CHR$, 37

LEN, 38

STR$, 38

VAL, 38

Manipulation, 39

Sort, 40

Splitting, 39

Variable, 4

STR$, 38

Subroutine

Definition, 16

GOSUB, 16

Usage, 16 svar, 4

' T

Terminology, 1

Text rnodes, 46

120

Index

Text Modes Characters Program, H-7

Tokenized version, 3, 24

Tone, clipped, 57

TRAP, 22

Type-A-Tune Program, H-15

Untokenized version, 3

var, 4

Variable, 2 avoiding name limit, 2

Video Graffitti Program, H-12

Volume control, 57

Voice, 57

Window

Graphics, 47

Text, 47

Wraparound, 8

X-coordinate, 47

XIO, 29

XIO (Fill), 54

Y-coordinate, 47

Zero as Dummy Variable, 30, 34

TABLE OF MODES

AND SCREEN FORMATS

Gr.

Mode

Type

TEXT

GRAPHICS

Horiz.

(Columns)

160

320

Verl. (Rows)

Split

Screen

Verl. (Rows)

Full

Screen

160

192

ttOf

Colors

1/2

RAM

Required

(Bytes)

993

513

261

273

537

1017

2025

3945

7900

MODE, SET COLOR, COLOR TABLE

Default

Colors

LIGHT BLUE

DARK BLUE

BLACK

ORANGE

LIGHT GREEN

DARK BLUE

RED

BLACK

ORANGE

LIGHT GREEN

DARK BLUE

BLACK

ORANGE

BLACK

LIGHT GREEN

DARK BLUE

BLACK

Mode or

Condition

MODE 0 and

ALL TEXT

WINDOWS

MODES 1 and

(Text Modes)

MODES 3, 5, and 7

(Four-color modes)

MODES 4 and 6

(Two-color

Modes)

MODE 8

(1 Color

2 Luminances) o

4 o

SETCOLOR

(aexpl)

Color

Register No.

Color

(aexp)

COLOR data actually determines character to be plotted

COLOR data actually determines character to be

Plotted

• 3

DESCRIPTION AND COMMENTS

Character luminance (Same color as background)

Background

—

Border

Character

Background, Border

Graphics point

Graphics point (background default), Border

Graphics point

—

Graphics point (background default), Border

—

Graphics point luminance (same color as background)

Graphics point (background default) -:

—

Border

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Key features

BASIC language support
Graphics capabilities
Sound and game controllers
Screen wraparound
Keyboard rollover
Error message display
Peripheral device support
Built-in functions
Array and matrix manipulation
String manipulation

Frequently asked questions

Direct mode allows you to execute instructions immediately after pressing RETURN, without using line numbers. Deferred mode uses line numbers and delays execution of instructions until the RUN command is entered.

Pressing the BREAK key during program execution causes execution to stop. You can resume execution by typing CONT followed by pressing RETURN.

To clear the screen in Direct mode, type CLEAR and press RETURN. To clear the screen in Deferred mode, type PRINT " ", press ESC, then press CLEAR.