Typical PC hardware

* Central processing unit (CPU) - Performs most of the calculations which enable a computer to function, sometimes referred to as the "brain" of the computer.
o Computer fan - Used to lower the temperature of the computer; a fan is almost always attached to the CPU, and the computer case will generally have several fans to maintain a constant airflow. Liquid cooling can also be used to cool a computer, though it focuses more on individual parts rather than the overall temperature inside the chassis.
* Random Access Memory (RAM) - Fast-access memory that is cleared when the computer is powered-down. RAM attaches directly to the motherboard, and is used to store programs that are currently running.
* Firmware is loaded from the Read only memory ROM run from the Basic Input-Output System (BIOS) or in newer systems Extensible Firmware Interface (EFI) compliant


* Internal Buses - Connections to various internal components.
o PCI
o PCI-E
o USB
o HyperTransport
o CSI (expected in 2008)
o AGP (being phased out)
o VLB (outdated)
o ISA (outdated)
o EISA (outdated)
o MCA (outdated)


* External Bus Controllers - used to connect to external peripherals, such as printers and input devices. These ports may also be based upon expansion cards, attached to the internal buses.
o parallel port
o serial port
o USB
o firewire
o SCSI (On Servers and older machines)
o PS/2 (For mice and keyboards, being phased out and replaced by USB.)
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The motherboard is the "heart" of the computer, through which all other components interface.