37 lines
2.3 KiB
Markdown
37 lines
2.3 KiB
Markdown
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jsbasic
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=======
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Applesoft BASIC in JavaScript
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This is hosted at http://calormen.com/applesoft/
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Depends on various polyfills at: http://calormen.com/polyfill
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Notes & Known Issues
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--------------------
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* The BASIC program is compiled to JavaScript before execution. Syntax errors are therefore detected at compile-time rather than at run-time as on a traditional interpreter. For example, the following program would run without errors on an Apple since the erroneous second statement is never reached. `10 END : CHR$(PRINT)`
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* Handling of BASIC code that does not match the canonical `LIST` output format may not behave as on an Apple:
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* Keyword parsing differs from Applesoft command line. For example `FOR I = S TO P` doesn't collapse into `FOR I = STOP`.
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* The interpreter doesn't actually care about line numbers for statement ordering (just for `GOTO/GOSUB` targets and `IF` statements). So `20 PRINT "A", 10 PRINT "B"` will just print `A`, then `B`
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* To improve readability, lines may start with : and continue the previously numbered line.
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* Floating point overflow is only detected on variable assignment.
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* The DOS operating system implements only a subset of DOS 3.3 and ProDOS useful for basic file I/O.
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* Except for a small number of compatibility shims for common operations (e.g. keyboard strobe), commands that refer to assembly routines (`PEEK`, `POKE`, `CALL`, `USR` etc.), shape tables, or tape I/O are not implemented.
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* Commands that operate on the program itself (LIST, RUN, DEL, etc.) are not implemented.
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You can run your basic programs from the command line (with only basic text input and output, and no graphics or DOS commands):
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* On Windows, download basic.js and run from a command prompt via: `cscript.exe basic.js your_basic_program.txt`
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* On Mac/Linux, install Mozilla Rhino, download basic.js and run from the command prompt via: `java -jar PATH_TO/js.jar basic.js your_program.txt`
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To Do
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-----
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Implement DOS functionality for consoles
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Links
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-----
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[6502asm.com](http://www.6502asm.com/) - a 6502 assembler/emulator in JavaScript
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[Quite BASIC](http://www.quitebasic.com/) - a similar project aimed at teaching programming
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[NG-BASIC for Javascript](http://navahogunleg.net/blog/my-projects/ng-basic/) Navaho Gunleg's interpreter
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[BASIC Programming Resources](http://www.nicholson.com/rhn/basic/)
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[Apple II emulator in JavaScript](http://www.scullinsteel.com/apple2/)
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