A Central Processing Unit (CPU) is the brains of any computer system. Every action of the computer eventually goes through the CPU. Current CPUs are housed on a single chip called the microprocessor.
History
The first CPUs were held circuit boards filled with transistors and were held in large steel cabinets. They are now small enough to fit in the smallest cell phone or MP3 player and are found in many common household devices.
Function
CPUs are responsible for executing the commands passed to it by the software. It is the central logic for the computer.
Types
CPUs can be grouped into the number of "cores" or processors there are in one integrated circuit. They include single-core, dual-core and quad-core processors.
Speed
A CPU's speed is measured in megahertz (MHz) or gigahertz (GHz). This number reflects the number of clock cycles the CPU can perform in one second.
Considerations
Each computer motherboard can only accept one type of CPU. The different CPUs are identified by their socket types. Therefore, if you want to upgrade your CPU to a different socket type, you must also upgrade your motherboard.