Applesoft BASIC Quick Reference

This is intended as a quick reference for the Applesoft BASIC Interpreter in JavaScript by Joshua Bell.

Extensions beyond Applesoft BASIC used in the interpreter are called out with footnotes.

See also:

Statements

Variable Control

CLEAR
Clear all variables
[LET] var = expr
Assign variable
DIM var( size [ , size2 ...] ) [ , var2( size [ , size2 ...] ) ... ]
Allocate array
DEF FN f(var ) = expr
Define function of a single variable [1]

Flow Control

GOTO
Go to line number
GOSUB line
Go to subroutine
RETURN
Return from subroutine
ON expr GOTO line [, line2 ... ]
Branch based on index (value = 1, 2, ...)
ON expr GOSUB line [, line2 ... ]
Subroutine branch based on index (value = 1, 2, ...)
POP
Convert last gosub into a goto
FOR var = start TO end [ STEP incr ]
Loop with counter variable
NEXT [var [, var ...] ]
End of loop(s)
IF expr THEN statement
IF expr GOTO line
Conditional; if expr is false, rest of line is skipped
END
Terminate program
STOP
Break, as if an error occurred

Error Handling

ONERR GOTO line
Set error hook
RESUME
Retry line that caused ONERR GOTO

Input/Output

PRINT expr [ [;,] expr2 ... ] [;]
Output text
INPUT [string ;] var [, var2 ... ]
Read line of input
GET var
Read single key
HOME
Clear text display
HTAB expr
Position text cursor horizontally
VTAB expr
Position text cursor vertically
INVERSE
Set output mode to black-on-white
FLASH
Set output mode to flashing
NORMAL
Set output mode to white-on-black
TEXT
Set display to text mode

Miscellaneous

REM [ comment ]
Begin a comment; rest of line is skipped
TRACE
Turn on trace mode (line numbers printed)
NOTRACE
Turn off trace mode

Inline Data

DATA value [, value2 ... ]
Define inline data [2]
READ var
Read the next DATA value
RESTORE
Restore the DATA pointer to the first value

Lo-Res Graphics

GR
Set display to lores mode, clear screen
COLOR= expr
Set lores color (0...15)
PLOT expr, expr
Plot lores point (x = 0...39, y = 0...40/48)
HLIN expr, expr AT expr
Plot horizontal line (x1, x2 at y)
VLIN expr, expr AT expr
Plot vertical line (y1, y2 at x)

Hi-Res Graphics

HGR
Set display to hires mode, clear screen
HGR2
Set display to hires mode (page 2), clear screen
HPLOT [TO] expr, expr [ TO expr, expr ] ...
Plot hires point/line (x=0...279, y=0...191)
HCOLOR= expr
Set hires color (0...7)

Hi-Res Shape Tables - NOT IMPLEMENTED

ROT= expr
Set hires shape table rotation (0...63)
SCALE= expr
Set hires shape table scale (1...255)
DRAW expr [ AT expr, expr ]
Draw hires shape table shape in color
XDRAW expr [ AT expr, expr ]
Draw hires shape table shape with XOR

Interpreter and Program State - NOT IMPLEMENTED

CONT
Continue from a STOP
DEL
Delete lines of program
LIST [ expr [, expr ] ]
List lines of program
NEW
Clear program and variables
RUN [ expr ]
Start program execution at line
SPEED= expr
Set character output delay

Native Platform Interaction - NOT IMPLEMENTED

CALL expr
Execute assembly code at address
HIMEM: expr
Set upper address of variable memory
IN# expr
Direct input from slot
LOMEM: expr
Set lower address of variable memory
WAIT expr, expr [, expr]
Wait until memory location masked by second argument equals third argument (or zero)

Cassette Tape - NOT IMPLEMENTED

LOAD
Load program from cassette
RECALL
Load variables from cassette
SAVE
Save program to cassette
STORE
Save variables to cassette
SHLOAD
Load hires shape table from cassette

Compatibility Shims

POKE expr, expr
Set memory location to value
PR# expr
Direct output to slot

Functions

Numeric Functions

ABS( expr )
Absolute value of number
ATN( expr )
Arctangent of number
COS( expr )
Cosine of number
EXP( expr )
Raise e to number
INT( expr )
Integer part of number
LOG( expr )
Natural log of number
RND( expr )
Pseudo-random number generator (0 repeats last, negative reseeds)
SGN( expr )
Sign of number (-1,0,1)
SIN( expr )
Sine of number
SQR( expr )
Square root of number
TAN( expr )
Tangent of number

String Functions

LEN( expr )
Length of string
LEFT$( expr, expr )
Left portion of (string, length)
MID$( expr, expr [, expr] )
Substring of (string, start character, length)
RIGHT$( expr, expr )
Right portion of (string, length)

Type Conversion Functions

ASC( expr )
ASCII code for first character of string
CHR$( expr )
Character at specified ASCII code point
STR$( expr )
String representation of number
VAL( expr )
Parse string into number

System Interaction Functions

FRE( expr )
Garbage collect strings (returns 0)
PDL( expr )
Paddle position (paddle number)
POS( expr )
Horizontal cursor position
SCRN( expr, expr )
Lores color at pixel (x,y)
USR( expr )
Execute assembly code at address, return accumulator value - NOT IMPLEMENTED

User Defined Functions

FN f( expr )
Execute user defined function [1]

Function Compatibility Shims

PEEK( expr )
Value at memory location - NOT IMPLEMENTED

Operators

Comparison Operators

=
Equality[3]
<
Less than
>
Greater than
<=
=<
Less than or equal
>=
=>
Greater than or equal
<>
><
Not equal

Boolean Operators

AND
Conjunction
OR
Disjunction
NOT
Negation

Arithmetic Operators

^
Exponentiation
*
Multiplication
/
Division
+
Addition
-
Subtraction

String Operators

+
String Concatenation

BNF Grammar for Expressions

For the even geekier in the audience...

    Expression               := OrExpression
    OrExpression             := AndExpression [ 'OR' AndExpression ... ]
    AndExpression            := RelationalExpression [ 'AND' RelationalExpression ... ]
    RelationalExpression     := AdditiveExpression [ ( '=' | '<' | '>' | '<=' | '=<' | '>=' | '=>' | '<>' | '><' ) AdditiveExpression ... ]
    AdditiveExpression       := MultiplicativeExpression [ ( '+' | '-' ) MultiplicativeExpression ... ]
    MultiplicativeExpression := PowerExpression [ ( '*' | '/' ) PowerExpression ... ]
    PowerExpression          := UnaryExpression [ '^' UnaryExpression ]
    UnaryExpression          := ( '+' | '-' | 'NOT' ) UnaryExpression 
                              | FinalExpression
    FinalExpression          := number-literal
                              | string-literal 
                              | 'FN' user_function_name '(' Expression ')' 
                              | function_name '(' Expression [, Expression ...] ')' 
                              | identifier [ '(' Expression [, Expression ...] ')' ]
                              | '(' Expression ')'

DOS 3.3 / ProDOS Quick Reference

See also

DOS Commands

MON[,C][,I][,O]
Traces DOS 3.3 commands ('Commands', 'Input' and 'Output')
NOMON[,C][,I][,O]
Cancels tracing of DOS 3.3 commands ('Commands', 'Input' and 'Output')
OPEN filename[,Llen]
Opens a text file.
APPEND filename
Appends to a text file.
CLOSE [filename]
Closes specified (or all) open text files.
POSITION filename[,Rnum]
Advances position in text file.
READ filename[,Rnum][,Bbyte]
Reads from a text file.
WRITE filename[,Rnum][,Bbyte]
Writes to a text file
DELETE filename
Delete a file

Other DOS commands are NOT IMPLEMENTED.

Some sample files are present in a server-side store loaded on-demand into a client-side virtual file system (VFS). Creating or writing to a file will write to the VFS. Subsequent reads will read from the VFS. Files may be deleted from the VFS. These changes will not persist if the browser is refreshed or closed.

Extensions beyond Standard Applesoft