Appendix A: Commodore 64 BASIC V2

Here is a short summary of the commands for the built in Commodore 64 BASIC V2. Note that this is not intended to be a tutorial, but just a quick reference to refresh long unused brain cells.
If you are looking for a BASIC tutorial, take a look at the original C64 manual. It is available as etext at: http://project64.c64.org

In C64 BASIC V2 there are only few types of variables:

Float: This is the most frequently used type. Float-variables do not carry a type identifier.
Range +/- [2.94E-39 ... 1.70E+38] (+/- [2^-128 ... 2¹²⁷])
Precision: 32 bit mantisse (approx. 9.6 decimal digits) + 8 bit exponent
Integer (16 Bit): This is a rarely used type. Integer variables carry a '%' at the end of their name (eg. X%). Note that all computations are performed with float precision and conversion to Integer is only performed when the value is assigned to a variable. Thus Integer math is SLOWER (!) than Float math.
Boolean Results are expressed using Integers. FALSE is represented by 0 (0x0000) and TRUE by -1 (0xFFFF) or any other non-zero value.
Strings: String variables carry a '$' at the end of their name (eg. X$). Strings can be at most 255 characters long.

Only the first TWO (!) characters of a variable name are significant. Thus 'CO', 'COCOS' and 'COLLOSEUM' (but not 'C' and 'CA') are equivalent names for a single variable. On the other hand the type identifier is used to distinguish variables. Therefore 'CO', 'CO%' and 'CO$' are three different variables.

Program Flow Control

FOR...TO...STEP...NEXT - The only real loop construct in BASIC: Syntax:
FOR <Var> = <Start> TO <End> [STEP <Size>] <Loop Code> NEXT [<Var>]

Examples: FOR I=1 TO 5: PRINT I;: NEXT -> 1 2 3 4 5 FOR I=1 TO 5 STEP 2: PRINT I;: NEXT -> 1 3 5 FOR I=5 TO 1 STEP -2: PRINT I;: NEXT I -> 5 3 1 FOR I=3 TO 1: PRINT I;: NEXT -> 3 (!)
IF...THEN - Conditional Program Execution: Note: There is no such thing as ELSE or ENDIF.

Syntax:
IF <Condition> THEN <Statements> or
IF <Condition> GOTO <LineNr> or
IF <Condition> THEN <LineNr>

Example:
100 IF A < B THEN MN = A: GOTO 120 110 MN = B 120 ....
GOTO or GO TO - Unconditional Jump: Syntax:
GOTO <LineNr> or
GO TO <LineNr>
GOSUB - Unconditional Jump to Subroutine: Note that it is not possible to use formal parameters to a subroutine. Everything must be done using global variables.

Syntax:
GOSUB <LineNr>

Example:
10 PRINT "Main Program" 20 GOSUB 100 30 PRINT "Back To Main" 40 GOSUB 100 50 PRINT "Once again Main" 60 END 100 PRINT "This is the Subroutine" 110 RETURN
RETURN - Return from Subroutine: Syntax:
RETURN

Example:
See GOSUB
ON...GOTO or ON...GOSUB - Multiway branch: Syntax:
ON <IntegerExpr> GOTO <LineNr1>, <LineNr2> ...
or ON <IntegerExpr> GOSUB <LineNr1>, <LineNr2> ...

Example:
ON X GOTO 100, 200, 300
This is equivalent to:
IF X = 1 THEN GOTO 100 IF X = 2 THEN GOTO 200 IF X = 3 THEN GOTO 300
DEF FN- Define a BASIC Function/Subroutine: Syntax:
DEF FN <Name>(<Param>) = <Single Line Expression>

Example:
DEF FN SI(X) = SIN(X)/X FN SI(π/3) -> 0.816993343

Input/Output

GET - Read One Character from Standard Input without waiting: Syntax:
GET <VarName>

Example:
100 GET A$: IF A$ = "" THEN GOTO 100 -> Wait for any Key
INPUT - Get Data from Standard Input (usually Keyboard): Syntax:
INPUT [<Prompt>;] <VarName> [, <VarName> ...]

Examples:
INPUT "LOGIN:"; LG$ INPUT "Please Enter A, B and C"; A, B, C INPUT A
PRINT - Write to Standard Output (usually Screen): Syntax:
PRINT <Data> or
? <Data>

Examples:
PRINT "Hello World" PRINT "Here", "are", "Tabs" -> Note the ',' PRINT "First Line"; -> Note the ';' PRINT "Still the same line" PRINT "Power"; 2*32
SPC - Advance the Cursor by a specific Number of Steps: Syntax:
SPC(<Cnt>)

Example:
SPC(6)
TAB- Advance the Cursor to a Specific Position: Syntax:
TAB(<Place>)

Example:
TAB(6)
POS - Current Cursor Position: Syntax:
POS(<Dummy>)

Files

LOAD- Load a Program from Disk or Tape: Syntax:
LOAD <FileName> [, <Device> [, <SecondDev>]]

Examples:
LOAD "SuperGame", 8, 1 -> Absolute Load from Disk #8 LOAD "*", 9 -> Load the first program from Disk #9 LOAD "", 1 -> Load the first program from Tape (#1)
SAVE - Save a Program to Disk or Tape: Syntax:
SAVE <FileName> [, <Device> [, <SecondDev>]]

Example:
SAVE "SuperGame", 8 -> Save to Disk #8
To overwrite an existing file on a disk, prefix the filename with '@'

Example:
SAVE "@SuperGame",8 -> Save to Disk #8, overwriting an old file
VERIFY - Check if the Program in Memory and a Program on Disk or Tape are equal. Do not modify anything.: Syntax:
VERIFY <FileName> [, <Device> [, <SecondDev>]]

Examples:
VERIFY "SuperGame", 8 -> Check SuperGame from Disk #8 VERIFY "*", 9 -> Check the first program from Disk #9 VERIFY "", 1 -> Check the first program from Tape #1
OPEN- Open a File: Syntax:
OPEN <FileID>, <Device> [, <SecondDev> [, <FNameMode>]]
The <SecondDev> is an optional integer in the range 0-15 with the following meaning: 0..Used for LOAD, 1..Used for SAVE, 2-14..Freely usable for User File Access, 15..Command/Error Channel.
<FNameMode> uses the format: "<FileName> [,<FileType> [,<AccessMode>]]" where <FileType> is one of P (Program), S (Sequential), L (Relative) or U (User) and <AccessMode> is one of R (Read), W (Write), A (Append) or the number of Bytes/Record for Relative Files.

Examples:
OPEN 1, 4 -> Open a Output File to the Printer #4 OPEN 1, 8, 2, "My File,P,R" -> Open a Program for Reading OPEN 1, 8, 2, "My File,S,W" -> Open a Sequential File for Writing OPEN 1, 8, 2, "My File,L,"+CHR$(40) -> Open a Relative File with 40 Bytes/Record OPEN 1, 8, 15 -> Open the Disk Command/Error Channel
CLOSE - Close a File: Syntax:
CLOSE <FileID>

Example:
CLOSE 1
GET# - Read One Character from a File: Syntax:
GET# <FileID>, <VarName>

Example:
GET#1, A$

Note that there is no space between 'GET' and '#'.
INPUT# - Get Data from a File: Syntax:
INPUT# <FileID>, <VarName> [, <VarName>...]

Example:
INPUT#1, EN$, ER$, TR$, SC$

Note that there is no space between 'INPUT' and '#'.
PRINT#: Syntax:
PRINT# <FileID>, <Data>

Example:
PRINT#1, "Power64"

Note that there is no space between 'PRINT' and '#'. Note also that ?# is not PRINT# also they look the same in a listing.
CMD - Redirect Standard Output (Input is not affected) and writes a Message to it: Syntax:
CMD <FileID> [, <Message>]

Example:
OPEN 1, 4 ; Open a File#1 on Printer#4 CMD 1 ; Make it the standard Output PRINT "Whatever Output you want" PRINT "More Output" PRINT#1 ; Undo CMD 1 CLOSE 1
ST - Device Status (Built-In Variable): ST = 0 .. Device Ok
Bit 6: 1 .. End of File
Bit 7: 1 .. Device Not Present
READ - Read Static Data from DATA Statements in the Program: Syntax:
READ <Var> [, <Var>...]

Example:
10 RESTORE 20 READ X$ 30 PRINT X$; 40 S = 0 50 FOR I=1 TO 3 60 READ X 70 S = S + X 80 NEXT I 90 PRINT S 100 DATA "Power", 12, 34, 18
RESTORE - Set Pointer to Next DATA element to the first DATA statement in the program.: Syntax:
RESTORE

Example:
See READ
DATA- Store Static Data: Syntax:
DATA <Data> [, <Data>...]

Example:
See READ

Math Functions

LET - Assignment: Syntax:
LET <Variable> = <Value>

Example LET A = 6.25

Note the LET keyword is not necessary. <Variable> = <Value> is all that is needed. LET only slows things down -> Don't use it!
DIM - Array Declaration: Syntax:
DIM <Name>(<Size> [, <Size>...])

Examples:
DIM A(7) -> An array of 8(!) elements indexed [0..7]
DIM B$(4,5) -> An array of 30(!) strings
Usage of Elements: A(3) = 17 : B$(2,3) = "Power64"
+, -, *, /, ^ - Arithmetic Operators: Example:
9 + 5 * (15 - 1) / 7 + 2^4 -> 35
<, <=, =, <>, >=, > - Comparison Operators: Examples:
3 <> 6 -> -1 (TRUE)
3 > 4 -> 0 (FALSE)
SIN - Sine (Argument in Radians): Syntax:
SIN(<Value>)

Example:
SIN(π/3) -> 0.866025404
COS - Cosine (Argument in Radians): Syntax:
COS(<Value>)

Example:
COS(π/3) -> 0.5
TAN - Tangent (Argument in Radians): Syntax:
TAN(<Value>)

Example:
TAN(π/3) -> 1.73205081
ATN - Arcus Tangent (Result in [-π/2 .. π/2]): Syntax:
ATN(<Value>)

Example:
ATN(1) -> 0.785398163 ( = π/4)
EXP - Exponent (e^x where e = 2.71828183...): Syntax:
EXP(<Value>)

Example:
EXP(6.25) -> 518.012825
LOG - Natural Logarithm: Syntax:
LOG(<Value>)

Example:
LOG(6.25) -> 1.83258146
SQR - Square Root: Syntax:
SQR(<Value>)

Example:
SQR(6.25) -> 2.5
ABS - Absolute Value: Syntax:
ABS(<Value>)

Examples:
ABS(-6.25) -> 6.25 ABS(0) -> 0 ABS(6.25) -> 6.25
SGN - Sign: Syntax:
SGN(<Value>)

Examples:
SGN(-6.25) -> -1 SGN(0) -> 0 SGN(6.25) -> 1
INT - Integer (Truncate to greatest integer less or equal to Argument.): Syntax:
INT(<Value>)

Examples:
INT(-6.25) -> -7 (!) INT(-5) -> -5 INT(0) -> 0 INT(5) -> 5 INT(6.25) -> 6
RND - Random Number in [0.0 .. 1.0]: Syntax:
RND(<Seed>)
If (<Seed> < 0) the Random number generator is initialized

Examples:
RND(-625) -> 3.85114436E-06 RND(0) -> 0.464844882 RND(0) -> 0.0156260729

Logic & Binary Operators

Recall the encoding of Boolean Values:
FALSE <--> 0 (0x0000) and TRUE <--> -1 (0xFFFF) or any non-zero value

AND- Logical & Binary AND: Syntax:
<Expr> AND <Expr>

Examples:
A>5 AND X<=Y 12 AND 10 -> 8 (%1100 AND %1010 = %1000)
OR - Logical & Binary OR: Syntax:
<Expr> OR <Expr>

Examples:
A>5 OR X<=Y 12 OR 10 -> 14 (%1100 OR %1010 = %1110)
NOT- Logical & Binary NOT: Syntax:
NOT <Expr>

Examples:
NOT A>5 NOT 2 -> -3 (NOT $0002 = $FFFD)

Character & String Processing

+ - Concatenate Strings: Example:
"Pow" + "er64" -> "Power64"
<, <=, =, <>, >=, > - Comparison Operators: Examples:
"C64" < "Power64" -> -1 (TRUE) "Alpha" > "Omega" -> 0 (FALSE)
LEN - Stringlength: Syntax:
LEN(<String>)

Example:
LEN("Power64") -> 7
LEFT$ - Left part of a string: Syntax:
LEFT$(<String>, <Len>)

Example:
LEFT$("Power64", 5) -> "Power"
RIGHT$ - Right part of a string: Syntax:
RIGHT$(<String>, <Len>)

Example:
RIGHT$("Power64", 5) -> "wer64"
MID$ - Middle part of a string: Syntax:
MID$(<String>, <Start>, <Len>)

Example:
MID$("Power64 for Macintosh", 13, 3) -> "Mac"
/* -- 123456789012345678901 -- */
STR$ - Convert a Number into a String: Syntax:
STR$(<Value>)

Examples:
STR$(6.25) -> " 6.25" STR$(-6.25) -> "-6.25"
VAL - Convert a String to a Number: Syntax:
VAL(<String>)

Examples:
VAL("6.25") -> 6.25 VAL("6xx25") -> 6 VAL("x6x25") -> 0
ASC- ASCII code of the first character of a string: Syntax:
ASC(<String>)

Examples:
ASC("P") -> 80 ASC("Power64") -> 80
CHR$ - Character with a specific ASCII code: Syntax:
CHR$(<Value>)

Example:
CHR$(80) -> "P"

Memory Access

PEEK - Read Byte from Memory: Syntax:
PEEK(<Addr>)

Example:
PEEK(53280) -> Current Frame Color
POKE - Write Byte to Memory: Syntax:
POKE <Addr>, <Value>

Example:
POKE 53280, 7 -> Yellow Frame
WAIT - Wait until a Byte in Memory has a specific value: Syntax:
WAIT <Addr>, <Mask> [, <Invert>]
WAIT will halt the program until ((PEEK(<Addr>) EXOR <Invert>) AND <Mask>) != 0
If <Invert> is not specified it is assumed to be 0.

Example:
WAIT 198, 255 -> Wait for a key in the key buffer.

Interface to Assembler Programs

SYS - System - Call a Assembler Program: Syntax:
SYS <Addr> [, <Param> ...]

The number of parameters depends on the actual program called.
USR- User Command: Syntax:
USR(<Param>)

Similar to SYS but the <Addr> is fixed to $0310 and the first and only <Param> is already evaluated and stored in FloatAccu1 (FAC1) when the Assembler Program is called. Less flexible than SYS and thus rarely used.

Program Execution

RUN - Start the BASIC Program: Syntax:
RUN [<Line>]

If no <Line> is given, the program is started on its first line.

Example:
RUN
STOP- Stops program execution: Syntax:
STOP

STOP is similar to END, but prints the message BREAK IN <Line> when executed.
END - End program execution: Syntax:
END
CONT - Continue program execution: Syntax:
CONT

When program execution has interrupted by STOP, END or the Run/Stop key, the command CONT can be used to resume execution.

Miscellaneous

REM - Remark: Syntax:
REM <Text>

Example:
REM This line contains a comment
LIST - Display the listing of the current BASIC program: Syntax:
LIST [<Line> | <From>- | -<To> | <From>-<To>]
Without argument, the entire program is listed.

Examples:
LIST LIST -40 LIST 100-200
NEW - Delete the current program and all variables from memory: Syntax:
NEW

If the NEW command was accidentally issued, the deleted program can be recovered by using the NEW Magician described in Section 7.2.
CLR - Delete all variables: Syntax:
CLR
FRE - Free Memory: Syntax:
FRE(<Dummy>)

Example:
FRE(0) -> -26627 (immediately after Power-on)

Returns the number of Bytes free for BASIC programs as a signed 16 Bit integer. If the free memory exceeds 32KByte then a negative number (the actual number of free Bytes - 65536) will be returned. Thus -26627 should be read as 65536-26627 = 38909.
π - Pi = 3.14159265
TI - Timer Ticks since Power-On (1 Tick = 1/60 Second)
TI$ - Timer since Power-On in Hour/Minute/Second Format: TI$ (but not TI) can be assigned a value!
The accuracy of the Timer is very poor (>1% drift)

Source: http://www.infinite-loop.at/Power64/Documentation/Power64-ReadMe/AA-C64_BASIC.html
Power64 Homepage: http://www.infinite-loop.at and http://www.salto.at - EMail:
© Roland Lieger, Goethegasse 39, A-2340 Mödling, Austria - Europe
Last Changed: Feb. 29, 2008