5. Bitwise Operations
In this section, you will learn the assembly instructions that operate on the bits. The bits are numbered starting from the far right; the rightmost bit (least significant bit) has a bit position of 0, and the bit position increases toward the left. The left-most bit is called the most significant bit. The following is an example showing the bits and the bit positions for a byte, 5D (0101 1101). The same logic applies to a word, dword, and qword:
One of the bitwise instructions is the not instruction; it takes only one operand (which serves as both the source and destination) and inverts all of the bits. If eax contained FF FF 00 00 (11111111 11111111 00000000 00000000), then the following instruction would invert all of the bits and store it in the eax register. As a result, the eax would contain 00 00 FF FF (00000000 00000000 11111111 11111111):
not eax
The and, or, and xor instructions perform bitwise and, or, and xor operations and store the results in the destination...
