basic

10 PRINT "Hello World"

This guide is written specifically for the Sunflower BASIC implementation, but it should still give a general idea of how to use the language's primitives which are also found in most BASIC implementations.

Introduction

A BASIC program begins with line numbers, control-flow is done by jumping to absolute line numbers which point to compiled BASIC code data. 0 is not a valid line number.

15 LET A=0
20 PRINT "Hello BASIC"
25 LET A=A+1
30 IF A=10 GOTO 50
40 GOTO 20
50 END

Interpreter

Expressions can include numbers, variables and arithmetic operators. Numbers are decimal, but can be prefixed with $ for hexadecimal, there are no precedence rules.

10 LET A=6+7
20 PRINT 52+$20*A
30 END

Valid expressions arithmetic operators are +-*/%, bitwise operators are &|, logic operators are <>=!. The smallest number is -32768, the largest number is 32767.

Variables

Variables are single character uppercased letters of the alphabet. Some variables have special properties, here is the complete list:

R, reads a random number.
W, reads the screen width.
H, reads the screen height.

For example, if you wanted to do a program to roll a 6-sided dice using the R(random) variable.

10 PRINT "You rolled " R%6+1 "."
30 END

You rolled 5.

Loops

Using a variable as counter, a program can loop over a number of lines five times:

10 LET I=0
20 PRINT "Count: " I
25 LET I=I+1
30 IF I<5 GOTO 20
40 END

Count: 0
Count: 1
Count: 2
Count: 3
Count: 4

Interaction

The INPUT statement, will halt the execution and wait for an input. This can be used to store a value into a variable. For example, to capture the position of the mouse cursor:

10 PRINT "Touch the screen"
20 INPUT X, Y
30 PRINT "You touched at: " X ", " Y
50 PRINT "Press a button"
60 INPUT B
70 PRINT "You pressed: " B
80 END

Manual

Hypervisor	`RUN`	Used to begin program execution at the lowest line number.
	`RUN`	RUN
	`LIST`	Causes part or all of the user program to be listed. If no parameters are given, the whole program is listed. A single expression parameter in evaluated to a line number which, if it exists, is listed.
	`LIST`	LIST 200 LIST
	`CLEAR`	Formats the user program space, deleting any previous programs. If included in a program the program becomes suicidal when the statement is executed.
	`CLEAR`	CLEAR
Core	`REM`	Permits to add remarks to a program source.
	`REM`	REM This is a comment.
	`LET`	Assigns the value of an expression to a variable.
	`LET`	LET A=123/2, B=$20%2
	`IF`	If the result of the expression is not zero, the statement is executed; if False, the associated statement is skipped.
	`IF`	IF A>B-2 PRINT "A is greater."
	`GOTO`	Changes the sequence of program execution.
	`GOTO`	GOTO 50+A>B
	`END`	Must be the last executable statement in a program. Failure to include an END statement will result in an error stop after the last line of the program is executed.
	`END`	END
Subroutines	`GOSUB`	Changes the sequence of program execution, and remembers the line number of the GOSUB statement, so that the next occurrence of a RETURN statement will result in execution proceeding from the statement following the GOSUB.
	`GOSUB`	GOSUB 220
	`RETURN`	Transfers execution control to the line following the most recent unRETURNed GOSUB. If there is no matching GOSUB an error stop occurs.
	`RETURN`	RETURN
I/O	`PRINT`	Prints the values of the expressions and/or the contents of the strings in the console. To print the result of an expression as an ascii character, use `#$41`, to print the character A, end with a semi-colon to print without a linebreak.
	`PRINT`	PRINT "The result is: " A+B
	`INPUT`	Halts evaluation, and assigns the result of expressions to each of the variables listed in the argument. Expressions are entered sequencially and separated by a line break, a list of two arguments, will expect two input lines.
	`INPUT`	INPUT X, Y
File	`SAVE`	Exports your program to example.bas.
	`SAVE`	SAVE example.bas
	`LOAD`	Imports the example.bas program, replaces your current program.
	`LOAD`	LOAD example.bas
Screen	`COLOR`	Sets the interface RGB colors, see theme.
	`COLOR`	COLOR $50f2, $b0f9, $a0f8
	`CLS`	Clears the screen.
	`CLS`	CLS
	`DRAW`	Sets position of drawing.
	`DRAW`	DRAW 100, 320
	`MODE`	Sets drawing mode, see varvara.
	`MODE`	MODE 04
	`SPRITE`	Draws a sprite, uses MODE.
	`SPRITE`	SPRITE $1c1c, $087f, $0814, $2241
	`PICT`	Draws a picture from a file, uses MODE.
	`PICT`	PICT image10x10.icn

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