Short description of all Atari Basic instructions

Index

ABS
ADR
AND
ASC
ATN
BYE
CHR$
CLOAD
CLOG
CLOSE
CLR
COLOR
COM
CONT
COS
CSAVE
DATA
DEG
DIM
DOS
DRAWTO
END
ENTER
EXP
FOR
FRE
GET
GOSUB
GOTO
GO TO
GRAPHICS
IF
INPUT
INT
LEN
LET
LIST
LOAD
LOCATE
LOG
LPRINT
NEW
NEXT
NOT
NOTE
ON
OPEN
OR
PADDLE
PEEK
PLOT
POINT
POKE
POP
POSITION
PRINT
PTRIG
PUT
RAD
READ
REM
RESTORE
RETURN
RND
RUN
SAVE
SETCOLOR
SGN
SIN
SOUND
SQR
STATUS
STICK
STRIG
STEP
STOP
STR$
THEN
TO
TRAP
USR
VAL
XIO
?

ABS

Usage:
ABS(number_value)
Description:
Returns absolute value of given argument (ABS(-12.4) will be 12.4).
Examples:

ADR

Usage:
ADR(text_value)
Description:
Returns memory address of first char of string given as argument.
Examples: See also:

AND

Usage:
logical_value AND logical_value
Description:
Executes logical AND with given arguments. Returns TRUE (1) if both arguments are different from zero, or 0 otherwise.
Examples: See also:

ASC

Usage:
ASC(text_value)
Description:
Returns ASCII code of first char of string given as argument.
Examples: See also:

ATN

Usage:
ATN(number_value)
Description:
Returns arcus tangens of value given as argument. Returned value depends on kind of trigonometric unit (see RAD and DEG).
Examples: See also:

BYE

Usage:
BYE
Description:
Ends work in Atari Basic and executes SELF TEST.
Examples: See also:

CHR$

Usage:
CHR$(number_value)
Description:
Returns char represented by ASCII code given as argument.
Examples: See also:

CLOAD

Usage:
CLOAD
Description:
Removes program in memory and loads a new one from tape recorder. Program loaded by CLOAD must be saved by command CSAVE.
See also:

CLOG

Usage:
CLOG(number_value)
Description:
Returns decimal logarithm of value given as argument.
Examples: See also:

CLOSE

Usage:
CLOSE #number_value
Description:
Closes given IOCB. Contents of buffers is saved before closing channel.
Examples: See also:

CLR

Usage:
CLR
Description:
Clears all variables and Basic's stack. Removes all arrays and strings.
See also:

COLOR

Usage:
COLOR number_value
Description:
In char modes sets char using for PLOT and DRAWTO instructions. In pixel modes sets color register using for drawing. In mode 9 sets luminance and in mode 11 sets color for drawing.
Examples: See also:

COM

Usage:
COM number_variable(number_value[,number_value]), or
COM string_variable(number_value)
Description:
Works the same that DIM. Look for DIM.
Examples: See also:

CONT

Usage:
CONT
Description:
Resumes executing of program which has been stopped by: instruction STOP or END, pressing BREAK key, or error detection. Program would be executed from next line that line which program has been stopped at.
Examples: See also:

COS

Usage:
COS(number_value)
Description:
Returns cosinus of value given as argument. Returned value depends on kind of trigonometric unit (see RAD and DEG).
Examples: See also:

CSAVE

Usage:
CSAVE
Description:
Saves program on tape recorder. Program would be saved in tokenized form, with short breaks between records. Program saved by CSAVE can be loaded only by CLOAD.
See also:

DATA

Usage:
DATA constant[,constant,...]
Description:
DATA keeps strings and values that can be copied to variables by instruction READ.
Examples: See also:

DEG

Usage:
DEG
Description:
Sets degree as unit used by trigonometric functions. Devault unit is radian.
Examples: See also:

DIM

Usage:
DIM number_variable(number_value[,number_value]), or
DIM string_variable(number_value)
Description:
Defines arrays and strings and reserves memory space for them. Arguments defines maximal lenght of array or string. First element of number array has got index=0, and first char of string has got index=1. Number arrays may has up to two dimensions, strings (char arrays) - only one dimension.
Examples: See also:

DOS

Usage:
DOS
Description:
Ends work in Atari Basic and goes to Disk Operating System. If DOS hasn't been loaded, DOS goes to Self Test (just like BYE).
Examples: See also:

DRAWTO

Usage:
DRAWTO number_value,number_value
Description:
Draws line from actual position of cursor to point with coordinates given as arguments. Point 0,0 is at left top corner. First coordinate describes column (X), second - row (Y). Unlegal coordinate causes error 141.
Examples: See also:

END

Usage:
END
Description:
Closes all IOCB channels (except channel 0), turns off all sound generators and finishes executing of program. Program could be re-runned by CONT instruction. END instruction isn't required, because these actions take place also after executing last line of program.
Examples: See also:

ENTER

Usage:
ENTER file_spec
Description:
Reads lines from file given as argument. Lines are interpreted just like entered from keybord: if line is preceded by number, it is attached to the program, if it isn't, it is executed. Useful for linking programs.
Examples: See also:

EXP

Usage:
EXP(number_value)
Description:
Returns exponent of argument.
Examples: See also:

FOR

Usage:
FOR number_variable=number_value TO number_value [STEP number_value]
Description:
Executes all lines between FOR and NEXT as loop with counter. Lines are executed as long as counter is less than final value (given after word TO), but at least one time. After every executing counter is increased by value given after word STEP (if isn't present, it is assumed 1). Step value can be also less then zero. Loops can also be imbedded.
Examples: See also:

FRE

Usage:
FRE(number_value)
Description:
Returns size of free memory, in bytes. Argument han't got any meaning, it could be any number value.
Examples:

GET

Usage:
GET #number_value,number_variable
Description:
Gets one byte from channel given as first argument and assign its value to variable given as second argument. If it is necessary (for example keyboard buffer is empty), waits for this byte. Channel had to be opened before.
Examples: See also:

GOSUB

Usage:
GOSUB number_value
Description:
Jumps to subroutine, which starts from line given as argument. GOSUB stores number of actual line on stack. Instruction RETURN will resume executing of program from this line.
Examples: See also:

GOTO

Usage:
GOTO number_variable
Description:
Jumps to line given as argument immediately. Doesn't remember number of line which jumps from. Could also be used in form GO TO.
Examples: See also:

GO TO

Usage:
GO TO number_variable
Description:
Works like a GOTO.
See also:

GRAPHICS

Usage:
GRAPHICS number_value
Description:
Sets graphics mode given as argument. There is 16 different graphics modes on Atari (from 0 to 15). Number could be increased by 16 to turn off text window, or by 32 to omit cleaning screen memory. GRAPHICS opens channel 6 for device S:.
Examples: See also:

IF

Usage:
IF number_value THEN number_constant|instruction
Description:
Tests the value for truth. It is truth if it isn't equal to zero. Logical expressions could also be used. If the expression is true, instruction placed after THEN or line with number given after THEN will be executed. If expression is false, next line will be executed.
Examples: See also:

INPUT

Usage:
INPUT [#number_value,]variable[,variable...]
Description:
Reads data from channel and assigns it to variable given as argument. If no channel is given, reads from channel 0. It displays then question mark (?). If it confuses you, use form INPUT #16,A.
Examples: See also:

INT

Usage:
INT(number_variable)
Description:
Returns integer part of given value. Result is always less or equal to argument, for example INT(-2.5)=-3.
Examples:

LEN

Usage:
LEN(text_value)
Description:
Returns actual lenght in chars of text string given as argument.
Examples: See also:

LET

Usage:
[LET] number_variable=number_value
[LET] text_variable=text_value
Description:
Assigns value to given variable. Word LET isn't necessary unless name of variable is Atari Basic keyword.
Examples:

LIST

Usage:
LIST [file_spec,][number_value[,number_value]]
Description:
Displays lines of program. If file_spec is given, listing is directed to this file. Program saved by LIST can be loaded by ENTER. If first number is given then only line with this number is displayed. If both numbers are given then all lines from first number to second number inclusive.
Examples: See also:

LOAD

Usage:
LOAD file_spec
Description:
Removes actual program and load a new one from file given as argument. Program should be stored with SAVE instruction.
See also:

LOCATE

Usage:
LOCATE number_value,number_value,number_variable
Description:
Gets value (char of color) of point with given coordinates and assigns this value to given variable. It is value of COLOR used to setting this point.
Examples: See also:

LOG

Usage:
LOG(number_value)
Description:
Returns natural logarithm (ln) of argument.
Examples: See also:

LPRINT

Usage:
LPRINT [value][[,]|[;][value]...]
Description:
Prints given values on printer. It is using channel 7. Separators like a comma or semicolon can be used to formatting data. Semicolon determines printing without any space between data. Comma determines printing next data at first column n*10.
Examples: See also:

NEW

Usage:
NEW
Description:
Closes all IOCB channels (except channel 0), turns off all sound generators, finishes executing of program and removes program from memory.
Examples: See also:

NEXT

Usage:
NEXT number_variable
Description:
Last instruction of FOR loop. It checks if counter is less then final value. If it is, increases it by step value and jumps to begin of loop. If it isn't, ends FOR loop.
Examples: See also:

NOT

Usage:
NOT number_value
Description:
Reverses logical value of given expression. If argument is equal to 0 then it returns 1, if it isn't equal to 0, it returns 0.
Examples: See also:

NOTE

Usage:
NOTE #number_value,number_variable,number_variable
Description:
Reads actual position of disk drive head and assign it to two given variables. First contains sector number, second contains byte number. These values can be used with POINT instruction.
Examples: See also:

ON

Usage:
ON number_value GOTO|GOSUB number_value[,...]
Description:
Tests given value and jumps to line indexed by this value or do nothing (if value is equal to 0). Value can't be less then 0, or greater then 255.
Examples: See also:

OPEN

Usage:
OPEN #number_value,number_value,number_value,file_spec
Description:
Opens given channel (from 1 to 7) for transmition with given device or file. Second and third argument describes transmition mode (read/write mode and AUX1 byte). Open channel can be used for other I/O instructions: GET, INPUT, NOTE, POINT, PRINT, PUT, XIO. After transmition channel should be closed with CLOSE instruction.
Examples: See also:

OR

Usage:
number_value OR number_value
Description:
Executes logical OR with given arguments. Returns FALSE (0) if both arguments are are equal to 0, or 0 otherwise.
Examples: See also:

PADDLE

Usage:
PADDLE(number_value)
Description:
Returns position of paddle manipulator connected to port with number given as argument. Result could be from 1 to 228 inclusive.
Examples: See also:

PEEK

Usage:
PEEK(number_value)
Description:
Returns byte from memory address given as argument.
Examples: See also:

PLOT

Usage:
PLOT number_value,number_value
Description:
Sets point with coordinates given as arguments. Point 0,0 is at left top corner. First coordinate describes column (X), second - row (Y). Unlegal coordinate causes error 141.
Examples: See also:

POINT

Usage:
POINT #number_value,number_value,number_value
Description:
Sets disk drive head to sector and byte given as arguments. These values can be taken by NOTE instruction.
Examples: See also:

POKE

Usage:
POKE number_value,number_value
Description:
Stores second value in byte with address given as first argument.
Examples: See also:

POP

Usage:
POP
Description:
Takes from Basic stack bytes placed there by last instruction GOSUB (6 bytes) or FOR (16 bytes). It makes accessible leaving FOR loop or subroutine by GOTO instruction.
Examples: See also:

POSITION

Usage:
POSITION number_value,number_value
Description:
Moves cursor to point with coordinates given as arguments. Cursor is visible only in graphics mode 0.
Examples: See also:

PRINT

Usage:
PRINT|? [#number_value[,|;]][value][,|;[value]...]
Description:
Writes to given channel values. If no channel is given writes to channel 0. Values must be separated by commas (,) or semicolons (;). Semicolon determines printing without any space between data. Comma determines printing next data at first column n*10. If it isn't separator at the end of values list, then EOL char is also sent. Values written to file can be read by INPUT instruction.
Examples: See also:

PTRIG

Usage:
PTRIG(number_value)
Description:
Returns state of button on paddle manipulator connected to the port given as argument. If button is pressed, it returns 0, or 1 otherwise.
Examples: See also:

PUT

Usage:
PUT #number_value,number_value
Description:
Writes byte given as second argument to channel given as first argument. Channel had to be opened before.
Examples: See also:

RAD

Usage:
RAD
Description:
Sets radian as unit used by trigonometric functions. Devault unit is radian.
Examples: See also:

READ

Usage:
READ variable[,variable]
Description:
Reads value from DATA line and assign it to given variable. Values are taken sequencely from one DATA instruction or from next DATA.
Examples: See also:

REM

Usage:
REM [any char string]
Description:
Do nothing. All words after REM (in this line) are ignored by interpreter. Can be used for comments.
Examples:

RESTORE

Usage:
RESTORE [number_value]
Description:
Causes reading datas from line given as argument, or from first DATA line, if no argument is given.
Examples: See also:

RETURN

Usage:
RETURN
Description:
Ends current subprogram and returns to line which this subprogram has been called from. Gets number of this line from Basic stack.
Examples: See also:

RND

Usage:
RND(number_value)
Description:
Returns random value from 0 to 1. Argument hasn't got any meaning, it could be any value.
Examples:

RUN

Usage:
RUN [file_spec]
Description:
If no argument is given, it does the same operations that END and CLR and then starts executing program in memory from its first line. If argument is given, it loads program from given file (just like LOAD) and starts its executing. Program must be stored by SAVE instruction.
Examples: See also:

SAVE

Usage:
SAVE file_spec
Description:
Stores program to file given as argument. Program is saved in tokenized form (similar to representation of program in memory). File can be read by LOAD or RUN.
Examples: See also:

SETCOLOR

Usage:
SETCOLOR number_value,number_value,number_value
Description:
Sets hue and luminance of colour register given as first argument. Second argument describe hue and third one - luminance.
Examples: See also:

SGN

Usage:
SGN(number_value)
Description:
Returns signum of argument. If argument is less then 0, it returns -1. If argument is greater then 0, it returns 1. If argument is equal to 0, it returns 0.
Examples:

SIN

Usage:
SIN(number_value)
Description:
Returns sinus of value given as argument. Result depends on unit of trigonometric functions.
Examples: See also:

SOUND

Usage:
SOUND number_value,number_value,number_value,number_value
Description:
Sets sound generator given as first argument (from 0 to 3) to plaing sound given as rest of arguments. Second argument (from 0 to 255) describes frequency, third one (from 0 to 15) - choose kind of roars (10 or 14 means no roars), fourth argument (from 0 to 15) describes volume of sound. If all three sound arguments are equal to 0, it turns off this generator.
Examples: See also:

SQR

Usage:
SQR(number_value)
Description:
Returns square root of argument. Argument must be greater or equal to 0.
Examples:

STATUS

Usage:
STATUS #number_value,number_variable
Description:
Reads operation status for IOCB channel given as first argument and assigns this value to given variable. Value 1 means SUCCESS.
Examples: See also:

STICK

Usage:
STICK(number_value)
Description:
Returns value which describes position of joystick connected to port given as first argument. Position values: 
     10  14  6
       \  | /
        \ |/
     11--15--7
        / |\
       /  | \
      9  13  5
Examples: See also:

STRIG

Usage:
STRIG(number_value)
Description:
Returns state of button on joystick connected to the port given as argument. If button is pressed, it returns 0, or 1 otherwise.
Examples: See also:

STEP

Description:
Optional part of the FOR instruction. Defines value which is added to loop counter after each executing of the loop. If no given, 1 is assumed.
See also:

STOP

Usage:
STOP
Description:
Breaks executing of program and displays message: STOPPED AT LINE n". Doesn't close IOCB channels and doesn't turn off sound generators. Executing of the program can be recovered by CONT instruction.
Examples: See also:

STR$

Usage:
STR$(number_value)
Description:
Returns string which is ASCII equivalent of number given as argument. Result is char string and it can contain chars like: numbers from 0 to 9, '-', '+' (only in exponent) and letter 'E'.
Examples: See also:

THEN

Description:
Part of the IF instruction. Precedes list of instructions which are executed, if logical expression is not equal to 0.
See also:

TO

Description:
Part of the FOR instruction. Describes final value of the loop counter.
See also:

TRAP

Usage:
TRAP number_value
Description:
Sets trap for error in line given as argument. When error occurs, it will not be error message, program will be continued from given line. Error code could be read by PEEK(195) and number of line which caused error could be read by PEEK(186)+256*PEEK(187). Error trapping is turned off by error detection or instruction TRAP with argument greater then 32767.
Examples:

USR

Usage:
USR(number_value[,number_value...])
Description:
Executes binary program in machine language placed from address given as first argument. Rest of arguments is stored on 6502 stack (LSB first, MSB second) and it can be used as arguments for binary program. Last byte placed on 6502 stack describes number of bytes to pull from it. After return from binary program (RTS code) Basic gets value from bytes 212 and 213. This value is returned as result of USR function.
Examples: See also:

VAL

Usage:
VAL(text_value)
Description:
Returns number value represented by string given as argument. Scans string to first unexpected char.
Examples: See also:

XIO

Usage:
XIO number_val,#number_val,number_val,number_val,file_spec
Description:
Universal IO instruction. It can handle all commands akcepted by CIO and the device. Some operation can be done by other Basic instruction (OPEN, GET, PRINT, STATUS...).
Examples: See also:

?

Description:
Abbreviation for PRINT instruction. Represented by another token, but works just like PRINT.
See also:

Last updated on 16-December-98
TMT