Itanium® Architecture for Programmers: Understanding 64-Bit Processors and EPIC Principles

Chapter 6. Logical Operations, Bit-Shifts, and Bytes

Logic provides the hardware-level foundation for both arithmetic calculations and control of flow in software. Although this chapter stays at the level of the instruction set architecture, we shall seek to demonstrate that integer arithmetic operations can be built out of logical operations applied in appropriate parallel and/or sequential manners.

Early in the twentieth century, tabulating machines processed demographic data from the US Census, printed address labels, and even issued payroll checks. Those electromechanical devices sorted stiff paper cards according to patterns of holes that represented printable characters—i.e., one character for each of up to 80 columns on a card. Because ...