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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>Introduction</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h2><a name="tag_01"></a>Introduction</h2><h3><a name="tag_01_01"></a>Scope</h3><p>The scope of IEEE Std 1003.1-2001 is described in the Base Definitions volume of IEEE Std 1003.1-2001.</p><h3><a name="tag_01_02"></a>Conformance</h3><p>Conformance requirements for IEEE Std 1003.1-2001 are defined in the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap02.html#tag_02">Chapter 2, Conformance</a>.</p><h3><a name="tag_01_03"></a>Normative References</h3><p>Normative references for IEEE Std 1003.1-2001 are defined in the Base Definitions volume ofIEEE Std 1003.1-2001.</p><h3><a name="tag_01_04"></a>Change History</h3><p>Change history is described in the Rationale (Informative) volume of IEEE Std 1003.1-2001, and in the CHANGE HISTORYsection of reference pages.</p><h3><a name="tag_01_05"></a>Terminology</h3><p>This section appears in the Base Definitions volume of IEEE Std 1003.1-2001, but is repeated here for convenience:</p><p>For the purposes of IEEE Std 1003.1-2001, the following terminology definitions apply:</p><h4><a name="tag_01_05_01"></a>can</h4><p>Describes a permissible optional feature or behavior available to the user or application. The feature or behavior is mandatoryfor an implementation that conforms to IEEE Std 1003.1-2001. An application can rely on the existence of the feature orbehavior.</p><h4><a name="tag_01_05_02"></a>implementation-defined</h4><p>Describes a value or behavior that is not defined by IEEE Std 1003.1-2001 but is selected by an implementor. The valueor behavior may vary among implementations that conform to IEEE Std 1003.1-2001. An application should not rely on theexistence of the value or behavior. An application that relies on such a value or behavior cannot be assured to be portable acrossconforming implementations.</p><p>The implementor shall document such a value or behavior so that it can be used correctly by an application.</p><h4><a name="tag_01_05_03"></a>legacy</h4><p>Describes a feature or behavior that is being retained for compatibility with older applications, but which has limitationswhich make it inappropriate for developing portable applications. New applications should use alternative means of obtainingequivalent functionality.</p><h4><a name="tag_01_05_04"></a>may</h4><p>Describes a feature or behavior that is optional for an implementation that conforms to IEEE Std 1003.1-2001. Anapplication should not rely on the existence of the feature or behavior. An application that relies on such a feature or behaviorcannot be assured to be portable across conforming implementations.</p><p>To avoid ambiguity, the opposite of <i>may</i> is expressed as <i>need not</i>, instead of <i>may not</i>.</p><h4><a name="tag_01_05_05"></a>shall</h4><p>For an implementation that conforms to IEEE Std 1003.1-2001, describes a feature or behavior that is mandatory. Anapplication can rely on the existence of the feature or behavior.</p><p>For an application or user, describes a behavior that is mandatory.</p><h4><a name="tag_01_05_06"></a>should</h4><p>For an implementation that conforms to IEEE Std 1003.1-2001, describes a feature or behavior that is recommended butnot mandatory. An application should not rely on the existence of the feature or behavior. An application that relies on such afeature or behavior cannot be assured to be portable across conforming implementations.</p><p>For an application, describes a feature or behavior that is recommended programming practice for optimum portability.</p><h4><a name="tag_01_05_07"></a>undefined</h4><p>Describes the nature of a value or behavior not defined by IEEE Std 1003.1-2001 which results from use of an invalidprogram construct or invalid data input.</p><p>The value or behavior may vary among implementations that conform to IEEE Std 1003.1-2001. An application should notrely on the existence or validity of the value or behavior. An application that relies on any particular value or behavior cannotbe assured to be portable across conforming implementations.</p><h4><a name="tag_01_05_08"></a>unspecified</h4><p>Describes the nature of a value or behavior not specified by IEEE Std 1003.1-2001 which results from use of a validprogram construct or valid data input.</p><p>The value or behavior may vary among implementations that conform to IEEE Std 1003.1-2001. An application should notrely on the existence or validity of the value or behavior. An application that relies on any particular value or behavior cannotbe assured to be portable across conforming implementations.</p><h3><a name="tag_01_06"></a>Definitions</h3><p>Concepts and definitions are defined in the Base Definitions volume of IEEE Std 1003.1-2001.</p><h3><a name="tag_01_07"></a>Relationship to Other Formal Standards</h3><p>Great care has been taken to ensure that this volume of IEEE Std 1003.1-2001 is fully aligned with the followingstandards:</p><dl compact><dt>ISO C (1999)</dt><dd><br>ISO/IEC 9899:1999, Programming Languages - C.</dd></dl><p>Parts of the ISO/IEC 9899:1999 standard (hereinafter referred to as the ISO C standard) are referenced to describerequirements also mandated by this volume of IEEE Std 1003.1-2001. Some functions and headers included within this volumeof IEEE Std 1003.1-2001 have a version in the ISO C standard; in this case CX markings are added as appropriate toshow where the ISO C standard has been extended (see <a href="#tag_01_08_01">Codes</a> ). Any conflict between this volume ofIEEE Std 1003.1-2001 and the ISO C standard is unintentional.</p><p>This volume of IEEE Std 1003.1-2001 also allows, but does not require, mathematics functions to supportIEEE Std 754-1985 and IEEE Std 854-1987.</p><h3><a name="tag_01_08"></a>Portability</h3><p>Some of the utilities in the Shell and Utilities volume of IEEE Std 1003.1-2001 and functions in the System Interfacesvolume of IEEE Std 1003.1-2001 describe functionality that might not be fully portable to systems meeting therequirements for POSIX conformance (see the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap02.html#tag_02">Chapter 2, Conformance</a>).</p><p>Where optional, enhanced, or reduced functionality is specified, the text is shaded and a code in the margin identifies thenature of the option, extension, or warning (see <a href="#tag_01_08_01">Codes</a> ). For maximum portability, an applicationshould avoid such functionality.</p><h4><a name="tag_01_08_01"></a>Codes</h4><p>Margin codes and their meanings are listed in the Base Definitions volume of IEEE Std 1003.1-2001, but are repeatedhere for convenience:</p><p><sup>[<a href="javascript:open_code('ADV')">ADV</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Advisory Information <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional. The functionality described is also an extension to the ISO C standard.</p><p>Where applicable, functions are marked with the ADV margin legend in the SYNOPSIS section. Where additional semantics apply to afunction, the material is identified by use of the ADV margin legend.</p><p><sup>[<a href="javascript:open_code('AIO')">AIO</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Asynchronous Input and Output <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional. The functionality described is also an extension to the ISO C standard.</p><p>Where applicable, functions are marked with the AIO margin legend in the SYNOPSIS section. Where additional semantics apply to afunction, the material is identified by use of the AIO margin legend.</p><p><sup>[<a href="javascript:open_code('BAR')">BAR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Barriers <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional. The functionality described is also an extension to the ISO C standard.</p><p>Where applicable, functions are marked with the BAR margin legend in the SYNOPSIS section. Where additional semantics apply to afunction, the material is identified by use of the BAR margin legend.</p><p><sup>[<a href="javascript:open_code('BE')">BE</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Batch Environment Services and Utilities <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional.</p><p>Where applicable, utilities are marked with the BE margin legend in the SYNOPSIS section. Where additional semantics apply to autility, the material is identified by use of the BE margin legend.</p><p><sup>[<a href="javascript:open_code('CD')">CD</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">C-Language Development Utilities <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional.</p><p>Where applicable, utilities are marked with the CD margin legend in the SYNOPSIS section. Where additional semantics apply to autility, the material is identified by use of the CD margin legend.</p><p><sup>[<a href="javascript:open_code('CPT')">CPT</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Process CPU-Time Clocks <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional. The functionality described is also an extension to the ISO C standard.</p><p>Where applicable, functions are marked with the CPT margin legend in the SYNOPSIS section. Where additional semantics apply to afunction, the material is identified by use of the CPT margin legend.</p><p><sup>[<a href="javascript:open_code('CS')">CS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Clock Selection <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional. The functionality described is also an extension to the ISO C standard.</p><p>Where applicable, functions are marked with the CS margin legend in the SYNOPSIS section. Where additional semantics apply to afunction, the material is identified by use of the CS margin legend.</p><p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Extension to the ISO C standard <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is an extension to the ISO C standard. Application writers may make use of an extension as it issupported on all IEEE Std 1003.1-2001-conforming systems.</p><p>With each function or header from the ISO C standard, a statement to the effect that "any conflict is unintentional" isincluded. That is intended to refer to a direct conflict. IEEE Std 1003.1-2001 acts in part as a profile of theISO C standard, and it may choose to further constrain behaviors allowed to vary by the ISO C standard. Such limitationsare not considered conflicts.</p><p>Where additional semantics apply to a function or header, the material is identified by use of the CX margin legend.</p><p><sup>[<a href="javascript:open_code('FD')">FD</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">FORTRAN Development Utilities <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional.</p><p>Where applicable, utilities are marked with the FD margin legend in the SYNOPSIS section. Where additional semantics apply to autility, the material is identified by use of the FD margin legend.</p><p><sup>[<a href="javascript:open_code('FR')">FR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">FORTRAN Runtime Utilities <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional.</p><p>Where applicable, utilities are marked with the FR margin legend in the SYNOPSIS section. Where additional semantics apply to autility, the material is identified by use of the FR margin legend.</p><p><sup>[<a href="javascript:open_code('FSC')">FSC</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">File Synchronization <img src="../images/opt-end.gif" alt="[Option End]" border="0"><br> The functionality described is optional. The functionality described is also an extension to the ISO C standard.</p><p>Where applicable, functions are marked with the FSC margin legend in the SYNOPSIS section. Where additional semantics apply to afunction, the material is identified by use of the FSC margin legend.</p>⌨️ 快捷键说明
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