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<p><strong>Reference</strong> <a class='wikilink' href='index.html'>Language</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 class='vspace'></p><h2>compound bitwise OR (|=)</h2>
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<h4>Description </h4>
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<p>The compound bitwise OR operator (|=) is often used with a variable and a constant to "set" (set to 1) particular bits in a variable.
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</p>
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<p class='vspace'></p><h4>Syntax:</h4>
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<pre>
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x |= y; // equivalent to x = x | y;
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</pre>
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<p class='vspace'></p><h4>Parameters</h4>
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<p>x: a char, int or long variable<br />y: an integer constant or char, int, or long
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<p class='vspace'></p><h4>Example:</h4>
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<p>First, a review of the Bitwise OR (|) operator
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</p><pre>
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0 0 1 1 operand1
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0 1 0 1 operand2
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----------
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0 1 1 1 (operand1 | operand2) - returned result
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</pre><p>Bits that are "bitwise <span class='wikiword'>ORed</span>" with 0 are unchanged, so if myByte is a byte variable,<br />
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myByte | B00000000 = myByte;
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</p>
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<p class='vspace'></p><p>Bits that are "bitwise <span class='wikiword'>ORed</span>" with 1 are set to 1 so:<br />myByte | B11111111 = B11111111;
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</p>
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<p class='vspace'></p><p>Consequently - to set bits 0 & 1 of a variable, while leaving the rest of the variable unchanged, use the compound bitwise AND operator (|=) with the constant B00000011
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</p><pre>
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1 0 1 0 1 0 1 0 variable
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0 0 0 0 0 0 1 1 mask
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----------------------
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1 0 1 0 1 0 1 1
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variable unchanged
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bits set
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</pre><p>Here is the same representation with the variables bits replaced with the symbol x
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</p>
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<p class='vspace'></p><pre>
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x x x x x x x x variable
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0 0 0 0 0 0 1 1 mask
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----------------------
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x x x x x x 1 1
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variable unchanged
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bits set
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</pre><p>So if:
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</p><pre>
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myByte = B10101010;
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myByte |= B00000011 == B10101011;
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</pre>
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<p class='vspace'></p><p>See Also
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</p><ul><li><a class='wikilink' href='BitwiseCompoundAnd.html'>&=</a> (compound bitwise and)
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</li><li><a class='wikilink' href='BitwiseAnd.html'>&</a> (bitwise and)
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</li><li><a class='wikilink' href='BitwiseAnd.html'>|</a> (bitwise or)
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</li></ul><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://arduino.cc/forum/index.php/board,23.0.html' 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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