82 lines
4.9 KiB
HTML
82 lines
4.9 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Passing parameters" />
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<meta name="abstract" content="In an OPM or ILE call, a parameter is an expression that represents a value that the calling application passes to the API specified in the call." />
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<meta name="description" content="In an OPM or ILE call, a parameter is an expression that represents a value that the calling application passes to the API specified in the call." />
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<title>Passing parameters</title>
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</head>
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<body id="conPassParm"><a name="conPassParm"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Passing parameters</h1>
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<div><p>In an OPM or ILE call, a parameter is an expression that represents
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a value that the calling application passes to the API specified in the call.</p>
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<p>HLL languages use the following methods for passing parameters:</p>
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<dl><dt class="dlterm"><em>By value, directly</em></dt>
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<dd> <p>The value of the data object is placed directly into the parameter
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list.</p>
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</dd>
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<dt class="dlterm"><em>By value, indirectly</em></dt>
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<dd> <p>The value of the data object is copied to a temporary location. The
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address of the copy (a pointer) is placed into the parameter list. By value,
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indirectly is not done explicitly by the application programmer. It is done
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by the operating system at run time.</p>
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</dd>
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<dt class="dlterm"><em>By reference</em></dt>
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<dd> <p>A pointer to the data object is placed into the parameter list. Changes
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made by the called API to the parameter are reflected in the calling application.</p>
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</dd>
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</dl>
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<p>When you call an API, the protocol for passing parameters is to typically
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pass a space pointer that points to the information being passed. (This is
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also referred to as pass-by-reference.) This is the convention used by the
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control language (CL), RPG, and COBOL compilers. Care must be used in those
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languages that support pass-by-value (such as ILE C) to ensure that these
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conventions are followed. Refer to the appropriate language documentation
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for instructions. The parameter passing convention of pass-by-reference can
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be used in all programming languages. Some of the UNIX-type APIs require pass-by-value
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parameter passing. VisualAge<sup>®</sup> C++ for <span class="keyword">i5/OS™</span> also
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supports pass-by-value parameter passing.</p>
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<p>HLL semantics usually determine when data is passed by value and when it
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is passed by reference. For example, ILE C passes and accepts parameters by
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value, directly, while for OPM and ILE COBOL and OPM and ILE RPG parameters
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are usually passed by reference. You must ensure that the calling program
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or procedure passes parameters in the manner expected by the called API. The
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OPM or ILE HLL programmer's guides contain more information on passing parameters
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to different languages.</p>
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<p>The ILE languages support the following parameter-passing styles:</p>
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<ul><li>ILE C passes and accepts parameters by value (directly and indirectly)
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and by reference.</li>
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<li>ILE COBOL supports the passing of parameters by value (indirectly) and
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by reference.</li>
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<li>ILE RPG supports the passing of parameters by value (directly and indirectly)
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and by reference.</li>
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<li>ILE CL supports the passing of parameters by reference.</li>
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</ul>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="conParameter.htm" title="After you have found the API that you want to use, you need to code a call to an API and pass to the API the required set of parameters appropriate for that API.">API parameters</a></div>
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</div>
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</div>
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</body>
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</html>
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