1<html lang="en"> 2<head> 3<title>isdigit - Untitled</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Untitled"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Ctype.html#Ctype" title="Ctype"> 9<link rel="prev" href="iscntrl.html#iscntrl" title="iscntrl"> 10<link rel="next" href="islower.html#islower" title="islower"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<meta http-equiv="Content-Style-Type" content="text/css"> 13<style type="text/css"><!-- 14 pre.display { font-family:inherit } 15 pre.format { font-family:inherit } 16 pre.smalldisplay { font-family:inherit; font-size:smaller } 17 pre.smallformat { font-family:inherit; font-size:smaller } 18 pre.smallexample { font-size:smaller } 19 pre.smalllisp { font-size:smaller } 20 span.sc { font-variant:small-caps } 21 span.roman { font-family:serif; font-weight:normal; } 22 span.sansserif { font-family:sans-serif; font-weight:normal; } 23--></style> 24<link rel="stylesheet" type="text/css" href="../cs.css"> 25</head> 26<body> 27<div class="node"> 28<a name="isdigit"></a> 29<p> 30Next: <a rel="next" accesskey="n" href="islower.html#islower">islower</a>, 31Previous: <a rel="previous" accesskey="p" href="iscntrl.html#iscntrl">iscntrl</a>, 32Up: <a rel="up" accesskey="u" href="Ctype.html#Ctype">Ctype</a> 33<hr> 34</div> 35 36<h3 class="section">3.5 <code>isdigit</code>—decimal digit predicate</h3> 37 38<p><a name="index-isdigit-114"></a><strong>Synopsis</strong> 39<pre class="example"> #include <ctype.h> 40 int isdigit(int <var>c</var>); 41 42</pre> 43 <p><strong>Description</strong><br> 44<code>isdigit</code> is a macro which classifies ASCII integer values by table 45lookup. It is a predicate returning non-zero for decimal digits, and 0 for 46other characters. It is defined only if <var>c</var> is representable as an 47unsigned char or if <var>c</var> is EOF. 48 49 <p>You can use a compiled subroutine instead of the macro definition by 50undefining the macro using `<code>#undef isdigit</code>'. 51 52 <p><br> 53<strong>Returns</strong><br> 54<code>isdigit</code> returns non-zero if <var>c</var> is a decimal digit (<code>0</code>–<code>9</code>). 55 56 <p><br> 57<strong>Portability</strong><br> 58<code>isdigit</code> is ANSI C. 59 60 <p>No supporting OS subroutines are required. 61 62 <p><br> 63 64 </body></html> 65 66