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| 22 | <title>Integer Variations (GNU C Language Manual)</title>
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| 32 | <link href="Integer-Types.html" rel="up" title="Integer Types">
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| 57 | <body lang="en">
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| 58 | <span id="Integer-Variations"></span><div class="header">
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| 59 | <p>
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| 60 | Previous: <a href="Boolean-Type.html" accesskey="p" rel="prev">Boolean Type</a>, Up: <a href="Integer-Types.html" accesskey="u" rel="up">Integer Types</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="Integer-Variations-1"></span><h4 class="subsection">11.1.6 Integer Variations</h4>
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| 64 |
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| 65 | <p>The integer types of C have standard <em>names</em>, but what they
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| 66 | <em>mean</em> varies depending on the kind of platform in use:
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| 67 | which kind of computer, which operating system, and which compiler.
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| 68 | It may even depend on the compiler options used.
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| 69 | </p>
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| 70 | <p>Plain <code>char</code> may be signed or unsigned; this depends on the
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| 71 | platform, too. Even for GNU C, there is no general rule.
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| 72 | </p>
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| 73 | <p>In theory, all of the integer types’ sizes can vary. <code>char</code> is
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| 74 | always considered one “byte” for C, but it is not necessarily an
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| 75 | 8-bit byte; on some platforms it may be more than 8 bits. ISO C
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| 76 | specifies only that none of these types is narrower than the ones
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| 77 | above it in the list in <a href="Basic-Integers.html">Basic Integers</a>, and that <code>short</code>
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| 78 | has at least 16 bits.
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| 79 | </p>
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| 80 | <p>It is possible that in the future GNU C will support platforms where
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| 81 | <code>int</code> is 64 bits long. In practice, however, on today’s real
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| 82 | computers, there is little variation; you can rely on the table
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| 83 | given previously (see <a href="Basic-Integers.html">Basic Integers</a>).
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| 84 | </p>
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| 85 | <p>To be completely sure of the size of an integer type,
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| 86 | use the types <code>int16_t</code>, <code>int32_t</code> and <code>int64_t</code>.
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| 87 | Their corresponding unsigned types add ‘<samp>u</samp>’ at the front.
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| 88 | To define these, include the header file <samp>stdint.h</samp>.
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| 89 | </p>
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| 90 | <p>The GNU C Compiler compiles for some embedded controllers that use two
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| 91 | bytes for <code>int</code>. On some, <code>int</code> is just one “byte,” and
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| 92 | so is <code>short int</code>—but that “byte” may contain 16 bits or even
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| 93 | 32 bits. These processors can’t support an ordinary operating system
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| 94 | (they may have their own specialized operating systems), and most C
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| 95 | programs do not try to support them.
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| 96 | </p>
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| 97 | <hr>
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| 98 | <div class="header">
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| 99 | <p>
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| 100 | Previous: <a href="Boolean-Type.html" accesskey="p" rel="prev">Boolean Type</a>, Up: <a href="Integer-Types.html" accesskey="u" rel="up">Integer Types</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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