Luftkatze's Standalone BASIC

Current version: v1.25

Variables

LK-BASIC does not give you any way to declare normal 'variables'. Instead, it gives you memory from VAR_OFFSET (0xB000) to 0xFFFF. To access this memory you use $ (word) and # (byte) operators. $xx returns word (2 bytes, 0 to 65535 (FFFF hex)) from xx+VAR_OFFSET, and #xx returns byte from xx+VAR_OFFSET. If xx+VAR_OFFSET is bigger than 0xFFFF program returns memory error (it should but it doesn't). To set variable's value you use VAR or PTR(PTR == VAR) keywords, eg. VAR 0=12, that translates to C's *(0+VAR_OFFSET)=12. VAR $0=12 coresponds to C's *(*(0+VAR_OFFSET))=12.

Program lines

LK-BASIC can interpret statements just after you press enter, or save statements to memory. To save statement to memory just type line number before statement, for example:

10 PRINT "Hello World!"
20 STOP

It is good to use numbers divisible by 10, if you do that you can insert lines between 10 and 20 without rewritting entire program. Statements are saved in [line_number*LINE_SIZE+CODE_START], where LINE_SIZE is 40 and CODE_START is 0x2000.

Statements

LK-BASIC supports 18 (plus 3 synonyms and 1 not working) statements ( [] is optional parameter, <> is required parameter):

• PRINT ["string"] [,] [variable [+|-|*] ] [;] - prints text on screen, for example PRINT "Hello World! Content of 0=",$0.
• REM [comment] - comment.
• VAR <address> = <value> - sets [number+VAR_OFFSET] to value, for example VAR 5=123.
• INPUT <address>[;] - sets [address] to user input (only number), for example INPUT 12. Without ; it prints ? before input.
• STOP - Stops program.
• IF <number> < == | != | \< | \> > <number> STATEMENT - does STATEMENT if condition is true, for example IF $0==12 GOTO 10.
• RND <address> - returns pseudo-random number in [address].
• INSTR <address> - reads line to address.
• CLS - clears screen.
• NEW - deletes program.
• LIST [line number] - lists program lines.
• GOTO <line number> - sets next line pointer to line number, for example GOTO 10 will go to 10th line of your code.
• BACK - returns to executing program after STOP statement.
• RUN - runs your program from line 1 until it reaches MAX_CODEOF or STOP instruction.
• GOSUB <line number> - same as GOTO, but saves next line number and is able to return to it using...
• RETURN - returns to last GOSUB statement.
• XY <x>,<y> - sets cursor position to x,y (x can be 0 to 79 and y 0 to 24 (80x25 screen)).
• PTR <address> = <value> - see: VAR.
• ? ["string"] [,] [variable [+|-|*] ] [;] - see: PRINT.
• IN <address>[;] - see: INPUT.
• GETCH <address> - gets character from keyboard buffer and saves in <address> (high = ASCII), for example GETCH 0.
• GETCHASYNC <address> - same as above but without waiting for keystroke (if buffer is empty returns 65535), for example GETCHASYNC 0.
• PUTARR <number [number [,] ...] > - puts char array on screen, for example PUTARR 65,66,67,13,10.
• POKE <address>,<value> - sets [address] to value, for example POKE 1025,0.
• PUTCH <ascii> put <ascii> on screen
• OUTNUMB <nr> put <nr> on screen as decimal number

Error messages

BASIC can return 3 errors:

• ?Number error - returned if number is beyond 16 bits
• ?Syntax error - basically every error.

Other stuff

What IS NOT supported yet?

• Separating statements by :.
• any form of loop.

Why is your code so bad?

tbh idk.

"Help! I'm stuck in infinite GOTO! How do I stop executing?!"

Ctrl+C is life Ctrl+C is love.