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Central processing unit

The central processing unit (CPU) is the part of a computer that interprets and carries out the instructions contained in the software. In most CPUs, this task is divided between a control unit that directs program flow and one or more execution units that perform operations on data. Almost always, a collection of registers is included to hold operands and intermediate results.

The term CPU is often used vaguely to include other centrally important parts of a computer such as caches and input/output controllers, especially in computers with modern microprocessor chips that include several of these functions in one physical integrated circuit.

Manufacturers and retailers of desktop computers often erroneously describe the computer case and its contents as the CPU which is misleading.

A family of CPU designs is often referred to as a CPU architecture.

Notable CPU architectures include:

Intel's x86 architecture
Zilog's architecture
IBM's System/360 architecture
DEC's PDP-11 architecture, and its successor, the VAX architecture
Motorola's 68000 architecture
Sun Microsystems's SPARC architecture
MIPS Computer Systems Inc.'s MIPS architecture
HP's PA-RISC architecture
DEC's Alpha architecture
The AIM Alliance's PowerPC architecture
DEC and Acorn ARM's StrongARM architecture
SuperH's SuperH architecture
UNIVAC 1100/2200 series architecture (currently supported by Unisys ClearPath IX computers)
1750A, the U.S.'s military standard computer.
AP-101, the space shuttle's computer

Emerging new CPU architectures include:

Intel's Itanium architecture
AMD's x86-64 architecture

Historically important CPUs have been:

EDSAC- the first stored-program computer
Apollo Guidance Computer, used in the moon flights

The above processor architectures could also be characterized by their CPU design like register size. Today most desktop computers have 32-bit processors; 64-bit processors are being phased in. Smaller devices like mobile phones, PDAs, or portable video game devices may have 16 or 8-bit processors.

See also