The Art of Assembly Language, 2nd Edition

2.7 Logical Operations on Binary Numbers and Bit Strings

The previous section defines the logical functions for single-bit operands. Because the 80x86 uses groups of 8, 16, or 32 bits, we need to extend the definition of these functions to deal with more than 2 bits. Logical functions on the 80x86 operate on a bit-by-bit (or bitwise) basis. Given two values, these functions operate on bit 0, producing bit 0 of the result. They operate on bit 1 of the input values, producing bit 1 of the result, and so on. For example, if you want to compute the logical and of the following two 8-bit numbers, you would perform the logical and operation on each column independently of the others:

%1011_0101
                         %1110_1110
                         ----------
                         %1010_0100

You may apply this bit-by-bit ...