BASIC

BASIC

Major implementations
Dartmouth BASIC Tiny BASIC Applesoft BASIC Atari BASIC Sinclair BASIC Commodore BASIC BBC BASIC TI-BASIC Casio BASIC Microsoft BASIC QB64 FreeBASIC Liberty BASIC PowerBASIC QuickBASIC

BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose high-level programming languages. The emergence of microcomputers in the 1970s led to the development of multiple dialects of BASIC, including Microsoft BASIC in 1975.

Data types and variables

Minimal versions of BASIC only support integer variables and one- or two-letter variable names. More powerful versions had floating-point arithmetic, and variables could be labelled with six or more letters. String variables are usually distinguished in many dialects by having the dollar sign $ suffixed to their name, and values were often identified by strings being delimited by double quotes " at the start and end.

Syntax

Data manipulation

Statement	Description	Example
LET	Assigns a value (which may be the result of an expression) to a variable.
DATA	Holds a list of values which are assigned sequentially using the READ command.
READ	Reads a value from a DATA statement and assigns it to a variable.
RESTORE	Resets the internal pointer to the first DATA statement, allowing the program to begin READing from the first value.
DIM	Sets up an array.

Flow control

Statement	Description	Example
IF ... THEN ... {ELSE}	Perform comparison and make decision which branches execution.
FOR ... TO ... {STEP} ... NEXT	Repeat a block of code the specified number of times.
WHILE ... WEND REPEAT ... UNTIL	Repeat a block of code while the specified condition is true. The condition may be evaluated before or after each iteration of the loop.
DO ... LOOP {WHILE} or {UNTIL}	Repeat a block of code indefinitely or until the specified condition is true.
GOTO	Jumps to a numbered or labelled line in the program.
GOSUB ... RETURN	Jumps to a numbered or labelled line in the program, executes the code until a RETURN statement is encountered, on which it jumps back to the statement following the original GOSUB.
ON ... GOTO/GOSUB	Chooses where to jump based on the specified condition.
DEF FN

Input and output

Statement	Description	Example
LIST	Displays the full source code of the current program.
PRINT	Displays a message on the screen or other output device.
INPUT	Asks the user to enter the value of a variable. The statement may include a prompt message.
TAB AT	Used with PRINT to set the position where the next character will be shown on the screen or printed on paper.
SPC	Prints out the specified number of space characters.

Math functions

Statement	Description	Example
ABS	Absolute value.
ATN	Arc tangent.
COS	Cosine.
EXP	Exponent.
INT	Integer part (typically floor).
LOG	Natural logarithm.
RND	Random number generation.
SIN	Sine.
SQR	Square root.
TAN	Tangent.

Miscellaneous

Statement	Description	Example
REM	Comment or REMark.
USR	Transfers control to a machine language subroutine.
CALL	Alternative form of USR.
TRON/TROFF	Turns on or off the display of each line number as it is run.
ASM	Inline assembly.