1<html lang="en"> 2<head> 3<title>Else - The C Preprocessor</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="The C Preprocessor"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Conditional-Syntax.html#Conditional-Syntax" title="Conditional Syntax"> 9<link rel="prev" href="Defined.html#Defined" title="Defined"> 10<link rel="next" href="Elif.html#Elif" title="Elif"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 141997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 152008, 2009, 2010, 2011 16Free Software Foundation, Inc. 17 18Permission is granted to copy, distribute and/or modify this document 19under the terms of the GNU Free Documentation License, Version 1.3 or 20any later version published by the Free Software Foundation. A copy of 21the license is included in the 22section entitled ``GNU Free Documentation License''. 23 24This manual contains no Invariant Sections. The Front-Cover Texts are 25(a) (see below), and the Back-Cover Texts are (b) (see below). 26 27(a) The FSF's Front-Cover Text is: 28 29 A GNU Manual 30 31(b) The FSF's Back-Cover Text is: 32 33 You have freedom to copy and modify this GNU Manual, like GNU 34 software. Copies published by the Free Software Foundation raise 35 funds for GNU development. 36--> 37<meta http-equiv="Content-Style-Type" content="text/css"> 38<style type="text/css"><!-- 39 pre.display { font-family:inherit } 40 pre.format { font-family:inherit } 41 pre.smalldisplay { font-family:inherit; font-size:smaller } 42 pre.smallformat { font-family:inherit; font-size:smaller } 43 pre.smallexample { font-size:smaller } 44 pre.smalllisp { font-size:smaller } 45 span.sc { font-variant:small-caps } 46 span.roman { font-family:serif; font-weight:normal; } 47 span.sansserif { font-family:sans-serif; font-weight:normal; } 48--></style> 49<link rel="stylesheet" type="text/css" href="../cs.css"> 50</head> 51<body> 52<div class="node"> 53<a name="Else"></a> 54<p> 55Next: <a rel="next" accesskey="n" href="Elif.html#Elif">Elif</a>, 56Previous: <a rel="previous" accesskey="p" href="Defined.html#Defined">Defined</a>, 57Up: <a rel="up" accesskey="u" href="Conditional-Syntax.html#Conditional-Syntax">Conditional Syntax</a> 58<hr> 59</div> 60 61<h4 class="subsection">4.2.4 Else</h4> 62 63<p><a name="index-g_t_0023else-90"></a>The ‘<samp><span class="samp">#else</span></samp>’ directive can be added to a conditional to provide 64alternative text to be used if the condition fails. This is what it 65looks like: 66 67<pre class="smallexample"> #if <var>expression</var> 68 <var>text-if-true</var> 69 #else /* Not <var>expression</var> */ 70 <var>text-if-false</var> 71 #endif /* Not <var>expression</var> */ 72</pre> 73 <p class="noindent">If <var>expression</var> is nonzero, the <var>text-if-true</var> is included and 74the <var>text-if-false</var> is skipped. If <var>expression</var> is zero, the 75opposite happens. 76 77 <p>You can use ‘<samp><span class="samp">#else</span></samp>’ with ‘<samp><span class="samp">#ifdef</span></samp>’ and ‘<samp><span class="samp">#ifndef</span></samp>’, too. 78 79 </body></html> 80 81