107 lines
7.2 KiB
HTML
107 lines
7.2 KiB
HTML
<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns:MadCap="http://www.madcapsoftware.com/Schemas/MadCap.xsd" MadCap:lastBlockDepth="6" MadCap:lastHeight="94" MadCap:lastWidth="853" MadCap:disableMasterStylesheet="true" MadCap:tocPath="" MadCap:InPreviewMode="false" MadCap:PreloadImages="false" MadCap:RuntimeFileType="Topic" MadCap:TargetType="WebHelp" lang="en-us" xml:lang="en-us" MadCap:PathToHelpSystem="../../../" MadCap:HelpSystemFileName="Default.xml" MadCap:SearchType="Stem">
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<head><title>ON...GOSUB</title>
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<link href="../../SkinSupport/MadCap.css" rel="stylesheet" />
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<link href="../../Resources/Stylesheets/BSE_Help.css" rel="stylesheet" />
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<script src="../../SkinSupport/MadCapAll.js" type="text/javascript">
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</head>
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<body>
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<h1 class="code">ON...GOSUB</h1>
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<div class="ImagePlusCaption">
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<div class="Col2">
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<p>
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<img src="../../graphics/pgm_icon2.gif" border="0" alt="BS2 icon" title="BS2 icon" />
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<img src="../../graphics/pgm_icon2e.gif" border="0" alt="BS2e icon" title="BS2e icon" />
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<img src="../../graphics/pgm_icon2sx.gif" border="0" alt="BS2sx icon" title="BS2sx icon" />
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<img src="../../graphics/pgm_icon2p.gif" border="0" alt="BS2p icon" title="BS2p icon" />
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<img src="../../graphics/pgm_icon2pe.gif" border="0" alt="BS2pe icon" title="BS2pe icon" />
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<img src="../../graphics/pgm_icon2px.gif" border="0" alt="BS2px icon" title="BS2px icon" /><span class="code_in_text"> {PBASIC 2.5}</span>
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</p>
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</div>
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<p style="text-align: right;"><a href="../ExampleTopics/OnGosubEx.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">ON...GOSUB Example</a>
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</p>
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<p> </p>
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</div>
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<p class="clear"> </p>
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<p> </p>
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<p class="PlainText">Syntax: <span class="keyword_in_text">ON</span> <![CDATA[ ]]><i>Offset</i> <![CDATA[ ]]><span class="keyword_in_text">GOSUB</span> <![CDATA[ ]]><i>Address1</i>, <i>Address2</i>, ...<i>AddressN</i></p>
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<h2>Function</h2>
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<p class="PlainText">Store the address of the next instruction after <span class="keyword_in_text">ON..GOSUB</span>, then go to the
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<i>Address</i> specified by offset (if in range) with the intention of returning
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to the stored address. If <i>Offset</i>-1 is greater than the number of elements in
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the address table, the program continues at the line following <span class="keyword_in_text">ON..GOSUB</span>.</p>
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<ul>
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<li value="1"><b><i>Offset</i></b> is a variable/constant/expression (0 - 255) that
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specifies the index of the address, in the list, to branch to (0 - N).</li>
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<li value="2"><b><i>Addresses</i></b> are labels that specify where to go for a given <i>Offset</i>. <span class="keyword_in_text">ON...GOSUB</span>
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will ignore any list entries beyond offset 255.</li>
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</ul>
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<h2>Quick Facts</h2>
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<table width="100%" cellpadding="4" cellspacing="0" border="1">
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<tr>
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<td align="center" width="25%" bgcolor="#CFCFCF"> </td>
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<td align="center" bgcolor="#CFCFCF">BS2 Family</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Limit of <i>Address</i> entries</td>
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<td align="center">256</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Maximum nested <span class="keyword_in_text">GOSUB</span>s </td>
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<td align="center">4</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Maximum <span class="keyword_in_text">GOSUB</span>s per Program</td>
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<td align="center">255 (each <span class="keyword_in_text">ON...GOSUB</span> counts as as a <span class="keyword_in_text">GOSUB </span>regardless of number of address list entries)</td>
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</tr>
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<tr>
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<td align="center" bgcolor="#CFCFCF">Related Commands</td>
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<td align="center" colspan="1">
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<p colspan="1" align="center"><a href="BRANCH.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">BRANCH</a>, <a href="GOSUB.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">GOSUB</a>, <a href="GOTO.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">GOTO</a>, <a href="ON_GOTO.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">ON...GOTO</a></p>
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</td>
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</tr>
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</table>
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<h2>Explanation</h2>
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<p class="PlainText">The <span class="keyword_in_text">ON...GOSUB</span> instruction is useful when you want to write something like
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this:</p><pre class="BScode" xml:space="preserve">
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IF (value = 0) THEN GOSUB Case_0
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IF (value = 1) THEN GOSUB Case_1
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IF (value = 2) THEN GOSUB Case_2
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</pre>
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<p class="PlainText">You can use <span class="keyword_in_text">ON...GOSUB</span> to organize this into a single statement:</p><pre class="BScode" xml:space="preserve">
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ON value GOSUB Case_0, Case_1, Case_2
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</pre>
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<p class="PlainText">This works exactly the same as the previous <a href="IF_THEN.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">IF…THEN</a> example. If the value isn't in range (in this case if <span class="code_in_text">value</span> is greater than 2), <span class="keyword_in_text">ON...GOSUB</span> does nothing and the program continues with the next instruction after <span class="keyword_in_text">ON</span>.</p>
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<div class="Col2">
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<div class="MasterFoot">
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<p MadCap:conditions="BSEconditions.BSEWebHelp (Primary)-INCLUDE"><a href="../../HomeTopics/HomePage.htm">Go to Welcome page</a>
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</p>
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<div class="MasterFoot">
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<p style="text-align: right;"><span class="ContactInfoProjectName">BASIC Stamp Help</span> <![CDATA[ ]]><span class="ContactInfoVersion#">Version 2.5.4</span> <![CDATA[ ]]></p>
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<p style="text-align: right;">Copyright © <span class="ContactInfoCompanyName">Parallax Inc.</span></p>
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<p style="text-align: right;"><span class="SystemShortDate">8/8/2012</span>
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</p>
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