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<!DOCTYPE html>
<html>
<head>
<title>Applesoft BASIC in JavaScript</title>
<link rel="Stylesheet" href="styles.css" type="text/css">
<meta http-equiv="X-UA-Compatible" content="IE=edge"> <!-- Suppress browser compat button -->
<script type="text/javascript" src="../polyfill/polyfill.js?update=2011-12-17"></script>
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<script type="text/javascript" src="../polyfill/keyboard.js"></script>
</head>
<body>
<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="#history">History</a>
<p>Related projects:
<a href="/Logo">Logo in Javascript</a>
| <a href="/vnIIc">Streaming video to an Apple II - vnIIc</a>
</p>
<br clear=left>
<!-- Screen -->
<div id="frame" class="frame" style="float: left; margin: 10px;">
<div id="screen-wrapper" class="wrapper">
<div id="lores" class="lores"></div>
<canvas id="hires" width="560" height="384" class="hires"></canvas>
<canvas id="hires2" width="560" height="384" class="hires"></canvas>
<div id="screen" class="tty"></div>
</div>
</div>
<!-- Keyboard - positioned offscreen -->
<input id="keyboard" class="keyboard" type="text" title="Hidden Keyboard Input Device">
<!-- Source -->
<div style="float: left; margin: 10px;">
Enter code below
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<input type="button" value="Run" id="btn_run">
<input type="button" value="Stop" id="btn_stop" disabled="disabled">
<select id="lb_files">
<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&apos;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&apos;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 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">
<!-- Source code editor inserted here -->
<div id="editorframe"></div>
<form id="submission" method="post" enctype="text/plain" action="mailto:inexorabletash@hotmail.com?subject=Applesoft%20Sample%20Submission">
<textarea name="source" id="source" style="display: none;">
</textarea>
<input type="submit" id="btn_share" value="Share your sample!">
<input type="button" id="btn_save" value="Save Program" title="Save the current program. NOTE: Can only save one program.">
<input type="button" id="btn_load" value="Load Program" title="Load a previously saved program. WARNING: The current program will be lost!">
</form>
</div>
<br clear=left>
<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&apos;t collapse into <code>FOR I = STOP</code>.
<li>The interpreter doesn&apos;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&apos;s interpreter
<li><a href="http://www.nicholson.com/rhn/basic/">BASIC Programming Resources</a>
</ul>
<h3 id="history">History</h3>
<div id="feed"></div>
<script src="cm2/lib/codemirror.js"></script>
<link rel="stylesheet" href="cm2/lib/codemirror.css">
<link rel="stylesheet" href="cm2/theme/default.css">
<script src="cm2/mode/basic/basic.js"></script>
<link rel="stylesheet" href="cm2/mode/basic/basic.css">
<style type="text/css">
.CodeMirror { border: solid 1px black; width: 598px; height: 384px; background-color: white; }
.CodeMirror-scroll { height: 100%; }
</style>
<script type="text/javascript" src="basic.js?2012-02-08"></script>
<script type="text/javascript" src="bell.js"></script>
<script type="text/javascript" src="tty.js"></script>
<script type="text/javascript" src="lores.js"></script>
<script type="text/javascript" src="hires.js"></script>
<script type="text/javascript" src="dos.js"></script>
<script type="text/javascript" src="printer.js"></script>
<script type="text/javascript" src="feed.js"></script>
<script type="text/javascript">
// not quite ready for jQuery...
var $ = function (id) { return document.getElementById(id); };
//
// Main
//
window.onload = function() {
$('lb_files').selectedIndex = 0;
var bell = (function() {
var b = new Bell(/^.*\/|/.exec(window.location)[0]);
return function() { b.play(); };
} ());
var tty = new TTY($('screen'), $('keyboard'), bell);
var dos = new DOS(tty);
var lores = new LoRes($('lores'), 40, 48);
var hires = new HiRes($('hires'), 280, 192);
var hires2 = new HiRes($('hires2'), 280, 192);
var display = {
state: { graphics: false, full: true, page1: true, lores: true },
setState: function(state, value /* ... */) {
var args = Array.prototype.slice.call(arguments);
while (args.length) {
state = args.shift();
value = args.shift();
this.state[state] = value;
}
if (this.state.graphics) {
lores.show(this.state.lores);
hires.show(!this.state.lores && this.state.page1);
hires2.show(!this.state.lores && !this.state.page1);
tty.splitScreen(tty.getScreenSize().height - (this.state.full ? 0 : 4));
}
else {
lores.show(false);
hires.show(false);
hires2.show(false);
tty.splitScreen(0);
}
}
};
var pdl = [0, 0, 0, 0];
// Lexical highlighting
var editor = new CodeMirror($('editorframe'), {
mode: 'basic',
tabMode: 'default',
content: $('source').value,
height: '100%'
});
$('btn_share').onclick = function() {
// Load up the hidden text area with the current source
$('source').value = getSource();
};
function getSource() {
return editor.getValue();
}
function setSource(source) {
editor.setValue(source);
}
// Do not let certain events take focus away from "keyboard"
function keyboardFocus(e) {
e = e ? e : window.event;
tty.focus();
e.cancelBubble = true; // IE
e.returnValue = false;
if (e.stopPropagation) { e.stopPropagation(); } // W3C
if (e.preventDefault) { e.preventDefault(); } // e.g. to block arrows from scrolling the page
return false;
}
$('lores').onclick = keyboardFocus;
$('hires').onclick = keyboardFocus;
$('hires2').onclick = keyboardFocus;
$('screen').onclick = keyboardFocus;
$('frame').onclick = keyboardFocus;
$('frame').onblur = keyboardFocus; // Needed on IE, not sure why it tries to get focus
$('keyboard').onfocus = function() { $('frame').style.backgroundColor = '#204020'; };
$('keyboard').onblur = function() { $('frame').style.backgroundColor = ''; };
var program;
$('btn_run').onclick = function() {
dos.reset();
tty.reset();
tty.autoScroll = true;
try {
program = basic.compile(getSource());
}
catch (e) {
if (e instanceof basic.ParseError) {
editor.setCursor({ line: e.line - 1, ch: e.column - 1 });
console.log(e.message +
' (source line:' + e.line + ', column:' + e.column + ')');
}
alert(e);
return;
}
stopped = false;
updateUI();
program.init({
tty: tty,
hires: hires,
hires2: hires2,
lores: lores,
display: display,
paddle: function(n) { return pdl[n]; }
});
setTimeout(driver, 0);
};
$('btn_stop').onclick = function() {
tty.reset(); // cancel any blocking input
stopped = true;
updateUI();
};
$('lb_files').onchange = function() {
var sel = $('lb_files');
loadFile('samples/' + sel.value + ".txt", setSource);
};
$('btn_save').onclick = function() { window.localStorage.setItem("save_program", getSource()); };
$('btn_load').onclick = function() { setSource(window.localStorage.getItem("save_program")); };
// Add a "printer" on demand
$('btn_capture').onclick = function() {
$('btn_capture').disabled = true;
var printer = new Printer(tty);
printer.onclose = function() {
$('btn_capture').disabled = false;
};
};
// Mouse-as-Joystick
var wrapper = $('screen-wrapper');
wrapper.onmousemove = function(e) {
e = e || window.event;
// compute relative coordinates
var x = e.clientX, y = e.clientY, elem = wrapper;
while (elem) {
x -= elem.offsetLeft - elem.scrollLeft;
y -= elem.offsetTop - elem.scrollTop;
elem = elem.offsetParent;
}
function clamp(n, min, max) { return Math.min(Math.max(n, min), max); }
pdl[0] = clamp(x / (wrapper.offsetWidth - 1), 0, 1);
pdl[1] = clamp(y / (wrapper.offsetHeight - 1), 0, 1);
};
var stopped = true;
function updateUI() {
$("btn_stop").disabled = stopped ? "disabled" : "";
$("btn_run").disabled = stopped ? "" : "disabled";
$("lb_files").disabled = stopped ? "" : "disabled";
if (stopped) {
$("btn_run").focus();
}
else {
tty.focus();
}
}
// TODO: Expose a RESPONSIVE |---+--------| FAST slider in the UI
// Number of steps to execute before yielding execution
// (Use a prime to minimize risk of phasing with loops)
var NUM_SYNCHRONOUS_STEPS = 37;
function driver() {
var state = basic.STATE_RUNNING;
var statements = NUM_SYNCHRONOUS_STEPS;
while (!stopped && state === basic.STATE_RUNNING && statements > 0) {
try {
state = program.step(driver);
}
catch (e) {
console.log(e);
alert(e.message ? e.message : e);
stopped = true;
updateUI();
return;
}
statements -= 1;
}
if (state === basic.STATE_STOPPED || stopped) {
stopped = true;
updateUI();
}
else if (state === basic.STATE_BLOCKED) {
// Fall out
}
else // state === basic.STATE_RUNNING
{
setTimeout(driver, 0); // Keep going
}
}
function loadFile(filename, callback) {
var req = new XMLHttpRequest();
var url = encodeURI(filename); // not encodeURIComponent, so paths can be specified
var async = true;
req.open("GET", url, async);
req.onreadystatechange = function() {
if (req.readyState === XMLHttpRequest.DONE) {
if (req.status === 200 || req.status === 0) // 0 for file:// protocol
{
callback(req.responseText);
}
}
}
req.send(null);
}
// load default
loadFile('samples/sample.default.txt', setSource);
// Show change history
atomToHtml('feed.xml?' + Math.random(), $('feed'));
};
</script>
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-18610679-3']);
_gaq.push(['_trackPageview']);
(function() {
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
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</script>
</body>
</html>