nit) The computing part of the computer. Also called the "processor," it is made up of the control unit and ALU. Today, the CPUs of almost all computers are contained on a single microprocessor chip. In fact, multiple processing units on one chip are commonplace (see multicore
). See microprocessor
, control unit
Computer Vs. Computer System
Technically, the CPU, clock and main memory make up a computer. A complete computer system requires the addition of peripheral control units, input, output and storage devices and an operating system. In practice, the terms "computer" and "computer system" are synonymous.
From the Old Mainframer's Viewpoint
Years ago, computer professionals involved with mainframes referred to the whole computer as the CPU, in which case, CPU referred to the processor, memory (RAM) and input/output channels.
Central Processing Units
Years ago, a CPU was the processor, memory and everything inside the cabinet. Today, a CPU is generally nothing more than a microprocessor.