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<title>define preprocessor</title>
<head>
<script language="JavaScript">
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<body bgcolor="#ffffcc">
<hr>
<center><h1>#define preprocessor</h1></center>
<hr>
<p>
The <b>#define</b> preprocessor allows us to define symbolic names and constants.
A quick example<p>
<pre>
#define PI 3.14159
</pre>
This statement will translate every occurance of PI in the program to 3.14159.
Here is a more complete example:<p>
<pre>
#define PI 3.14159
main()
{
int r=10;
float cir;
cir = PI * (r*r);
}
</pre>
This feature is partically usefull for defining 'magic' numbers.<p>
<hr>
<h2>See Also:</h2>
<ul>
<li>A related C keyword is <a href=enum.html>enum</a> which can be used to
build lists of aliases.<p>
<li>Another related C keyword is <a href=const.html>const</a>.
<p>
<li>An advanced use of #define is in the creation of <a href=macros.html>
macros</a>.
</ul>
<hr>
<h2>Examples:</h2>
<a href="../EXAMPLES/define.c"><img src="../../GRAPHICS/computer.gif"></a>
example program.<p>
<a href="../EXAMPLES/enum5.c"><img src="../../GRAPHICS/computer.gif"></a>
Conflict between enum and #define.<p>
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<address>Martin Leslie
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