The Art of Assembly Language, 2nd Edition

2.10 Shifts and Rotates

Another set of logical operations that apply to bit strings is the shift and rotate operations. These two categories can be further broken down into left shifts, left rotates, right shifts, and right rotates. These operations turn out to be extremely useful.

The left-shift operation moves each bit in a bit string one position to the left (Figure 2-8 provides an example of an 8-bit shift).

Figure 2-8. Shift-left operation

Bit 0 moves into bit position 1, the previous value in bit position 1 moves into bit position 2, and so on. There are, of course, two questions that naturally arise: "What goes into bit 0?" and "Where does the ...