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134 lines
6.8 KiB
HTML
134 lines
6.8 KiB
HTML
15 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html>
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<head>
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<title>Arduino - IntegerConstants </title>
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<p><strong>Reference</strong> <a class='wikilink' href='index.html'>Language</a> (<a class='wikilink' href='Extended.html'>extended</a>) | <a class='wikilink' href='Libraries.html'>Libraries</a> | <a class='wikilink' href='Comparison.html'>Comparison</a> | <a class='wikilink' href='Changes.html'>Changes</a>
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</p>
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<p class='vspace'></p><h2>Integer Constants</h2>
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<p>Integer constants are numbers used directly in a sketch, like <code>123</code>. By default, these numbers are treated as <a class='wikilink' href='Int.html'>int</a>'s but you can change this with the U and L modifiers (see below).
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</p>
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<p class='vspace'></p><p>Normally, integer constants are treated as base 10 (decimal) integers, but special notation (formatters) may be used to enter numbers in other bases.
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</p>
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<p class='vspace'></p><pre>
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Base Example Formatter Comment
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10 (decimal) 123 none
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2 (binary) B1111011 leading 'B' only works with 8 bit values (0 to 255)
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characters 0-1 valid
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8 (octal) 0173 leading "0" characters 0-7 valid
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16 (hexadecimal) 0x7B leading "0x" characters 0-9, A-F, a-f valid
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</pre>
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<p class='vspace'></p><p><strong>Decimal</strong> is base 10. This is the common-sense math with which you are acquainted. Constants without other prefixes are assumed to be in decimal format.
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</p>
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<p class='vspace'></p>Example:<pre>
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101 // same as 101 decimal ((1 * 10^2) + (0 * 10^1) + 1)
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</pre>
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<p><br />
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<strong>Binary</strong> is base two. Only characters 0 and 1 are valid.
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</p>
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<p class='vspace'></p>Example:<pre>
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B101 // same as 5 decimal ((1 * 2^2) + (0 * 2^1) + 1)
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</pre>
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<p>The binary formatter only works on bytes (8 bits) between 0 (B0) and 255 (B11111111). If it is convenient to input an int (16 bits) in binary form you can do it a two-step procedure such as:
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</p>
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<p class='vspace'></p><pre>
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myInt = (B11001100 * 256) + B10101010; // B11001100 is the high byte
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</pre>
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<p class='vspace'></p><p><strong>Octal</strong> is base eight. Only characters 0 through 7 are valid. Octal values are indicated by the prefix "0"
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</p>
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<p class='vspace'></p><p>Example:
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</p><pre>
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0101 // same as 65 decimal ((1 * 8^2) + (0 * 8^1) + 1)
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</pre><div class='indent'>Warning
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</div><div class='indent'>It is possible to generate a hard-to-find bug by (unintentionally) including a leading zero before a constant and having the compiler unintentionally interpret your constant as octal.
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</div><p><br />
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<strong>Hexadecimal (or hex)</strong> is base sixteen. Valid characters are 0 through 9 and letters A through F; A has the value 10, B is 11, up to F, which is 15. Hex values are indicated by the prefix "0x". Note that A-F may be syted in upper or lower case (a-f).
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</p>
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<p class='vspace'></p><p>Example:
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</p><pre>
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0x101 // same as 257 decimal ((1 * 16^2) + (0 * 16^1) + 1)
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</pre>
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<p class='vspace'></p><h4>U & L formatters</h4>
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<p>By default, an integer constant is treated as an <a class='wikilink' href='Int.html'>int</a> with the attendant limitations in values. To specify an integer constant with another data type, follow it with:
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</p>
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<p class='vspace'></p><ul><li>a 'u' or 'U' to force the constant into an unsigned data format. Example: <code>33u</code>
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</li><li>a 'l' or 'L' to force the constant into a long data format. Example: <code>100000L</code>
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</li><li>a 'ul' or 'UL' to force the constant into an unsigned long constant. Example: <code>32767ul</code>
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</li></ul><p><br />
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</p>
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<p class='vspace'></p><h4>See also</h4>
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<ul><li><a class='wikilink' href='Constants.html'>constants</a>
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</li><li><a class='wikilink' href='Define.html'>#define</a>
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</li><li><a class='wikilink' href='Byte.html'>byte</a>
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</li><li><a class='wikilink' href='Int.html'>int</a>
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</li><li><a class='wikilink' href='UnsignedInt.html'>unsigned int</a>
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</li><li><a class='wikilink' href='Long.html'>long</a>
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</li><li><a class='wikilink' href='UnsignedLong.html'>unsigned long</a>
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</li></ul><p class='vspace'></p><p><a class='wikilink' href='index.html'>Reference Home</a>
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</p>
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<p class='vspace'></p><p><em>Corrections, suggestions, and new documentation should be posted to the <a class='urllink' href='http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?board=swbugs' rel='nofollow'>Forum</a>.</em>
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</p>
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<p class='vspace'></p><p>The text of the Arduino reference is licensed under a
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<a class='urllink' href='http://creativecommons.org/licenses/by-sa/3.0/' rel='nofollow'>Creative Commons Attribution-ShareAlike 3.0 License</a>. Code samples in the reference are released into the public domain.
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