jsbasic/index.htm
2013-05-06 23:26:59 -04:00

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<title>Applesoft BASIC in JavaScript</title>
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<h1>Applesoft BASIC in Javascript</h1>
<p>
By <a href="mailto:inexorabletash@hotmail.com">Joshua Bell</a>
| <a target="_blank" href="reference.htm">Applesoft BASIC Quick Reference</a>
| <a href="#notes">Notes &amp; Known Issues</a>
| <a href="#todo">To Do</a>
| <a href="#links">Links</a>
| <a href="#changes">Changes</a>
<p>Related projects:
<a href="/Logo">Logo in Javascript</a>
| <a href="/vnIIc">Streaming video to an Apple II - vnIIc</a>
</p>
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<div id="lores" class="lores"></div>
<canvas id="hires" width="560" height="384" class="hires"></canvas>
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Enter code: &nbsp;&nbsp;
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<option disabled selected="selected">Select a file...</option>
<option value="sample.basic">DEMOS</option>
<option disabled>---- Tests ----</option>
<option value="sample.unittests">Unit Tests</option>
<option value="sample.keyboard">Keyboard Test</option>
<option value="sample.charset">Charset Test</option>
<option disabled>---- User Submissions ----</option>
<option disabled>Games</option>
<option value="simple.pong">SIMPLE.PONG</option>
<option value="sample.adventure">Text Adventure (Floyd McWilliams)</option>
<option value="sample.pacman">(Not Really) ASCII Pac-Man (Michael Kemp)</option>
<option value="sample.puzzler">Puzzler (Gregg Buntin)</option>
<option value="sample.hangman">Hangman (Mike Gleason)</option>
<option value="sample.raindrops">Catch the Raindrop (Nicholas Merchant)</option>
<option value="sample.jot">JOT (Mike Gleason)</option>
<option disabled>Graphics</option>
<option value="sample.rodscolorpattern">Rod's Color Pattern</option>
<option value="sample.hacker">Hacker Logo (markwstock)</option>
<option value="sample.loreswalk">Random LoRes (John Melesky)</option>
<option value="sample.hireswalk">Random HiRes (John Melesky)</option>
<option value="sample.sierpinski">Sierpinski Triangles (Kevin Miller)</option>
<option value="sample.stringart">String Art (Chris Heric)</option>
<option value="sample.paint">Drawing Program (Brian Broker)</option>
<option value="sample.scribble">Scribble (William Simms)</option>
<option value="sample.connections">Connections (Gregg Buntin)</option>
<option value="sample.squiggle">Squiggle (Gregg Buntin)</option>
<option value="sample.boys_surface">Boy's Surface (Lukas Innig)</option>
<option value="sample.gaussian">Gaussian Distribution 2D (John Russ)</option>
<option value="sample.bitmaps">Bitmap Images (Brian Broker)</option>
<option value="sample.mandelbrot">Mandelbrot Set (c/o Gregory Lewis)</option>
<option value="sample.mandelbrot2">Mandelbrot Set in Color</option>
<option value="sample.steve">Steve (Nicola Foggi)</option>
<option value="sample.logo">Apple Logo (Brendan Robert)</option>
<option disabled>Other</option>
<option value="sample.primes">Prime Sieve (Kevin Miller)</option>
<option value="sample.february">February Surprise (Antti Pirskanen)</option>
<option value="sample.hellosine">Hello World Sine Wave (Jamie Beu)</option>
<option value="sample.bodymass">Body Mass Index Calculator (Tim Dwyer)</option>
<option disabled>---- Traveller RPG Utilities ----</option>
<option value="TRADER C">TRADER</option>
<option value="sample.sectorgen">Traveller Sector Generator</option>
<option value="sample.zhorelay">Zhodani Relay Station Placement</option>
<option value="sample.readsector">Read Sector File</option>
</select>
<input type="button" id="btn_capture" value="Echo to &quot;Printer&quot;" title="Pops up a &quot;printer&quot; window and echoes all output there, so you can copy/paste">
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<h3 id="notes">Notes &amp; Known Issues</h3>
<ul>
<li>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. <code>10 END : CHR$(PRINT)</code>
<li>Handling of BASIC code that does not match the canonical <code>LIST</code> output format may not behave as on an Apple:
<ul>
<li>Keyword parsing differs from Applesoft command line. For example <code>FOR I = S TO P</code> doesn't collapse into <code>FOR I = STOP</code>.
<li>The interpreter doesn't actually care about line numbers for statement ordering (just for <code>GOTO</code>/<code>GOSUB</code> targets and <code>IF</code> statements). So <code>20 PRINT "A"</code>, <code>10 PRINT "B"</code> will just print A, then B
</ul>
<li>To improve readability, lines may start with <code>:</code> and continue the previously numbered line.
<li>Floating point overflow is only detected on variable assignment.
<li>The DOS operating system implements only a subset of DOS 3.3 and ProDOS useful for basic file I/O.
<li>Except for a small number of compatibility shims for common operations (e.g. keyboard strobe), commands that refer to assembly routines (<code>PEEK</code>, <code>POKE</code>, <code>CALL</code>, <code>USR</code> etc.), shape tables, or tape I/O are not implemented.
<li>Commands that operate on the program itself (<code>LIST</code>, <code>RUN</code>, <code>DEL</code>, etc.) are not implemented.
<li>You can run your basic programs from the command line (with only basic text input and output, and no graphics or DOS commands):
<ul>
<li>On Windows, download <a href="basic.js">basic.js</a> and run from a command prompt via:
<code>cscript.exe basic.js your_basic_program.txt</code>
<li>On Mac/Linux, install <a href="http://www.mozilla.org/rhino/">Mozilla Rhino</a>,
download <a href="basic.js">basic.js</a> and run from the command prompt via:
<code>java -jar PATH_TO/js.jar basic.js your_program.txt</code>
</ul>
</ul>
<h3 id="todo">To Do</h3>
<ul>
<li>Implement DOS functionality for consoles
</ul>
<h3 id="links">Links</h3>
<ul>
<li><a href="http://www.6502asm.com/">6502asm.com</a> - a 6502 assembler/emulator in JavaScript
<li><a href="http://www.quitebasic.com/">Quite BASIC</a> - a similar project aimed at teaching programming
<li><a href="http://navahogunleg.net/blog/my-projects/ng-basic/">NG-BASIC for Javascript</a> Navaho Gunleg's interpreter
<li><a href="http://www.nicholson.com/rhn/basic/">BASIC Programming Resources</a>
<li><a href="http://www.scullinsteel.com/apple2/">Apple II emulator in JavaScript</a>
</ul>
<h3 id="changes">Changes</h3>
<p>The source is tracked on <a href="http://github.com">GitHub</a> at <a href="https://github.com/inexorabletash/jsbasic/">https://github.com/inexorabletash/jsbasic/</a>.
<p>Older changes are documented in the <a href="https://github.com/inexorabletash/jsbasic/blob/master/CHANGELOG">CHANGELOG</a>
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