ation size is 32 bits. Using a REX prefix in the form of REX.R permits access to additional registers (R8-R15). Using a REX prefix in the form of REX.W promotes operation to 64 bits. See the summary chart at the beginning of this section for encoding data and limits.</p>
<h2>Operation</h2>
<pre>CF ← Bit(BitBase, BitOffset);
Bit(BitBase, BitOffset) ← 0;</pre>
<h2>Flags Affected</h2>
<p>The CF flag contains the value of the selected bit before it is cleared. The ZF flag is unaffected. The OF, SF, AF, and 