BASIC v2 language reference¶

Syntax highlighting support for Commodore 64 BASIC v2 (Commodore BASIC 2.0).

Control flow keywords¶

end, for, next, gosub, goto, if, then, step, stop, return, to, on

for i=1 to 10 step 2
    print i
next i

if x=5 then print "found"
on n gosub 100,200,300
gosub 1000
return
end

Built-in functions¶

BASIC v2 built-in functions categorized by purpose:

Mathematical functions¶

abs, atn, cos, exp, int, log, rnd, sgn, sin, sqr, tan

abs(x) - Absolute value
atn(x) - Arc tangent (result in radians)
cos(x) - Cosine (argument in radians)
exp(x) - Exponential (e^x)
int(x) - Integer portion (truncates toward zero)
log(x) - Natural logarithm (base e)
rnd(x) - Random number (0 ≤ result < 1)
sgn(x) - Sign function (-1, 0, or 1)
sin(x) - Sine (argument in radians)
sqr(x) - Square root
tan(x) - Tangent (argument in radians)

String functions¶

asc, chr$, left$, len, mid$, right$, str$, val

asc(str$) - Returns ASCII/PETSCII code of first character
chr$(code) - Converts numeric code to character
left$(str$,n) - Returns n leftmost characters
len(str$) - Returns string length (0-255)
mid$(str$,start,length) - Extracts substring
right$(str$,n) - Returns n rightmost characters
str$(num) - Converts number to string
val(str$) - Converts string to number

System functions¶

fre, peek, pos, usr

fre(0) - Returns free BASIC memory in bytes
peek(addr) - Reads byte from memory address
pos(0) - Returns cursor column position (0-39)
usr(x) - Calls machine language routine

a = abs(-5)
b$ = chr$(65)
c = peek(53280)
d$ = left$("hello",2)
m = fre(0)

User-defined functions¶

def fn declarations and fn function calls:

def fn sq(x) = x * x
a = fn sq(5)

I/O and disk keywords¶

print, print#, input, input#, open, close, load, list, save, restore, read, get, get#, poke, peek, sys, run, verify, wait

print "Hello"
input "Name";n$
open 1,8,2,"file,s,w"
load "program",8
poke 53280,0
sys 49152

Storage keywords¶

dim, data, let, def

dim array(10)
data 1,2,3,4,5
read a,b,c
let x = 42

Variables¶

Variable names with optional type suffixes:

Standard (float): a, counter - 40-bit floating point (default)
String: name$, text$ - Variable-length strings (up to 255 chars)
Integer: x%, count% - 16-bit signed (-32768 to 32767)

a = 10
name$ = "hello"
count% = 100

Variable naming rules¶

BASIC v2 enforces these constraints:

First two characters significant - counter and count are the same variable
Must start with letter - Cannot begin with digit or special character
Type suffix last - Dollar sign ($) or percent (%) must be final character
Case insensitive - NAME$ and name$ refer to same variable
Reserved words forbidden - Cannot use BASIC keywords as variable names

Operators¶

Arithmetic: +, -, *, /, ^
Comparison: =, <>, <, >, <=, >=
Logical: and, or, not

a = 5 + 3
if a>5 and b<10 then print "yes"

Numbers¶

Line numbers: At start of line (e.g., 10, 100)
Decimal: 255, 3.14159
Hexadecimal: $ff, $c000 (BPP+ preprocessor feature)
Binary: %11111111, %10101010 (BPP+ preprocessor feature)

10 a = 255
20 b = $ff
30 c = %11111111

Comments¶

REM comments: rem This is a comment
Semicolon comments: ; BPP+ comment syntax

rem BASIC comment
10 rem Comment after line number
; BPP+ comment

BPP+ removes both comment types during preprocessing. Exception: Blitz! compiler directives (rem **) are preserved.

Strings¶

Double-quoted strings and embedded PETSCII tokens:

a$ = "simple string"
b$ = "{clr}{wht}Hello"
c$ = "{10 space}Indented"

Token syntax inside strings:

Basic tokens: {clr}, {wht}, {down}
Repetition: {10 space}, {5 down}
Ranges: {a-z}, {0-9}

Extension symbols¶

See Extension symbols for MCI commands and Prof. Plum extensions.