Computer Hardware

**Computer hardware** is the physical part of a computer, including the digital circuitry, as distinguished from the computer software that executes within the hardware. The hardware of a computer is infrequently changed, in comparison with software and data, which are "soft" in the sense that they are readily created, modified or erased on the computer. Firmware is a special type of software that rarely, if ever, needs to be changed and so is stored on hardware devices such as read-only memory (ROM) where it is not readily changed (and is, therefore, "firm" rather than just "soft").

Most computer hardware is not seen by normal users. It is in embedded systems in automobiles, microwave ovens, electrocardiograph machines, compact disc players, and other devices. Personal computers, the computer hardware familiar to most people, form only a small minority of computers (about 0.2% of all new computers produced in 2003).

## Computer hardware

A typical personal computer consists of a case or chassis in a tower shape (desktop) and the following parts:

* Motherboard or system board with slots for expansion cards and holding parts
	+ Central processing unit, or CPU
		- Computer fan - used to cool down the CPU
	+ Random Access Memory, or RAM – for program execution and short term data storage, so the computer does not have to take the time to access the hard drive to find the file(s) it requires. More RAM will normally contribute to a faster PC. RAM is almost always removable as it sits in slots in the motherboard, attached with small clips. The RAM slots are normally located next to the CPU socket.
	+ Firmware usually Basic Input-Output System, or BIOS, based or in newer systems Extensible Firmware Interface (EFI) compliant
	+ Buses
		- Peripheral Component Interconnect (PCI)
		- PCI Express (PCI-E)
		- Universal Serial Bus (USB)
		- HyperTransport
		- Common System Interface (CSI) (expected in 2008)
		- Accelerated Graphics Port (AGP) (being phased out)
		- VESA Local Bus (VLB) (outdated)
		- Industry Standard Architecture (ISA) (outdated)
		- Extended Industry Standard Architecture (EISA) (outdated)
		- Micro Channel Architecture (MCA) (outdated)
* Computer power supply (Power supply) - a case that holds a transformer, voltage control, and (usually) a cooling fan
* Storage controllers of Integrated Drive Electronics (IDE), SATA, SCSI or other type, that control hard disk, floppy disk, CD-ROM and other drives; the controllers sit directly on the motherboard (on-board) or on expansion cards
* Graphics card that produces the output for the computer display]. This will either be built into the motherboard or attached in its own separate slot (PCI, PCI-E or AGP), requiring a Graphics Card.
* Computer bus controllers (parallel]], serial, USB], FireWire) to connect the computer to external peripheral devices such as printers or scanners
* Some type of a removable media writer:
	+ CD – the most common type of removable media, cheap but fragile.
		- CD-ROM Drive
		- CD Writer
	+ DVD
		- DVD-ROM Drive
		- DVD Writer
		- DVD-RAM Drive
	+ Blu-ray Disc
		- BD-ROM Drive
		- BD Writer
	+ Floppy disk
	+ Zip drive
	+ USB flash drive AKA a Pen Drive, memory stick
	+ Tape drive - mainly for backup and long-term storage
* Internal storage - keeps data inside the computer for later use.
	+ Hard disk - for medium-term storage of data.
	+ Disk array controller
* Sound card - translates signals from the system board into analog voltage levels, and has terminals to plug in speakers.
* Networking] - to connect the computer to the Internet and/or other computers
	+ Modem - for dial-up connections
	+ Network card - for DSL/Cable internet, and/or connecting to other computers.
* Other peripherals

In addition, hardware can include external components of a computer system. The following are either standard or very common.

* Input or Input devices
	+ Text input devices
		- Keyboard
	+ Pointing devices
		- Mouse
		- Trackball
	+ Gaming devices
		- Joystick
		- Gamepad
		- Game controller
	+ Image, [Video input devices
		- Image scanner
		- [Webcam
	+ Audio input devices
		- Microphone

* Output or Output devices
	+ Image, Video output devices
		- Printer Peripheral device that produces a hard copy. (Inkjet, Laser)
		- Monitor Device that takes signals and displays them. (CRT, LCD)
	+ Audio output devices
		- Speakers A device that converts analog audio signals into the equivalent air vibrations in order to make audible sound.
		- Headphones A device similar in functionality to computer speakers used mainly to not disturb others nearby.