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| 22 | <title>Type Qualifiers (GNU C Language Manual)</title>
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| 58 | <span id="Type-Qualifiers"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Functions.html" accesskey="n" rel="next">Functions</a>, Previous: <a href="Variables.html" accesskey="p" rel="prev">Variables</a>, Up: <a href="index.html" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Index.html" title="Index" rel="index">Index</a>]</p>
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| 61 | </div>
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| 62 | <hr>
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| 63 | <span id="Type-Qualifiers-1"></span><h2 class="chapter">21 Type Qualifiers</h2>
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| 64 |
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| 65 | <p>A declaration can include type qualifiers to advise the compiler
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| 66 | about how the variable will be used. There are three different
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| 67 | qualifiers, <code>const</code>, <code>volatile</code> and <code>restrict</code>. They
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| 68 | pertain to different issues, so you can use more than one together.
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| 69 | For instance, <code>const volatile</code> describes a value that the
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| 70 | program is not allowed to change, but might have a different value
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| 71 | each time the program examines it. (This might perhaps be a special
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| 72 | hardware register, or part of shared memory.)
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| 73 | </p>
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| 74 | <p>If you are just learning C, you can skip this chapter.
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| 75 | </p>
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| 76 | <table class="menu" border="0" cellspacing="0">
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| 77 | <tr><td align="left" valign="top">• <a href="const.html" accesskey="1">const</a></td><td> </td><td align="left" valign="top">Variables whose values don’t change.
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| 78 | </td></tr>
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| 79 | <tr><td align="left" valign="top">• <a href="volatile.html" accesskey="2">volatile</a></td><td> </td><td align="left" valign="top">Variables whose values may be accessed
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| 80 | or changed outside of the control of
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| 81 | this program.
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| 82 | </td></tr>
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| 83 | <tr><td align="left" valign="top">• <a href="restrict-Pointers.html" accesskey="3">restrict Pointers</a></td><td> </td><td align="left" valign="top">Restricted pointers for code optimization.
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| 84 | </td></tr>
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| 85 | <tr><td align="left" valign="top">• <a href="restrict-Pointer-Example.html" accesskey="4">restrict Pointer Example</a></td><td> </td><td align="left" valign="top">Example of how that works.
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| 86 | </td></tr>
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| 87 | </table>
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| 88 |
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| 89 |
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| 90 |
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| 91 |
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