Processing of Data

The operations of a digital computer are carried out by logic circuits, which are digital circuits whose single output is determined by the conditions of the inputs, usually two or more. The various circuits processing data in the computer's interior must operate in a highly synchronized manner; this is accomplished by controlling them with a very stable oscillator, which acts as the computer's "clock." Typical computer clock rates range from several million cycles per second to several hundred million, with some of the fastest computers having clock rates of about a billion cycles per second. Operating at these speeds, digital computer circuits are capable of performing thousands to trillions of arithmetic or logic operations per second, thus permitting the rapid solution of problems that would be impossible for a human to solve by hand. In addition to the arithmetic and logic circuitry and a small number of registers (storage locations that can be accessed faster than main storage and are used to hold the intermediate results of calculations), the heart of the computer-called the central processing unit, or CPU-contains the circuitry that decodes the set of instructions, or program, and causes it to be executed.