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    <p>Try:</p> <pre><code>x ^= 0x14; </code></pre> <p>That toggles both bits. It's a little bit unclear in question as you first mention swap and then give a toggle example. Anyway, to swap the bits:</p> <pre><code>x = precomputed_lookup [x]; </code></pre> <p>where precomputed_lookup is a 256 byte array, could be the fastest way, it depends on the memory speed relative to the processor speed. Otherwise, it's:</p> <pre><code>x = (x &amp; ~0x14) | ((x &amp; 0x10) &gt;&gt; 2) | ((x &amp; 0x04) &lt;&lt; 2); </code></pre> <p>EDIT: Some more information about toggling bits.</p> <p>When you xor (<code>^</code>) two integer values together, the xor is performed at the bit level, like this:</p> <pre><code>for each (bit in value 1 and value 2) result bit = value 1 bit xor value 2 bit </code></pre> <p>so that bit 0 of the first value is xor'ed with bit 0 of the second value, bit 1 with bit 1 and so on. The xor operation doesn't affect the other bits in the value. In effect, it's a parallel bit xor on many bits.</p> <p>Looking at the truth table for xor, you will see that xor'ing a bit with the value '1' effectively toggles the bit.</p> <pre><code> a b a^b 0 0 0 0 1 1 1 0 1 1 1 0 </code></pre> <p>So, to toggle bits 1 and 3, write a binary number with a one where you want the bit to toggle and a zero where you want to leave the value unchanged:</p> <pre><code>00001010 </code></pre> <p>convert to hex: 0x0a. You can toggle as many bits as you want:</p> <pre><code>0x39 = 00111001 </code></pre> <p>will toggle bits 0, 3, 4 and 5</p>
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    1. POSwap two bits with a single operation in C?
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    1. USTim Cooper
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    1. CODon't know why this was downvoted, it's as correct as the others.
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      1. USSkurmedel
    2. COAssuming the OP wants to toggle both bits (as opposed to interchange the two bits), this is the correct answer. OP is using the convention that the LSB is bit 0.
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      1. USAdam Rosenfield
    3. COIt's actually slightly more correct, since it's the only answer that operates on the right bits. Still just toggles the state and not *swaps*.
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