Computer

Typical PC hardware

Though a PC comes in many different form factors, a typical personal computer consists of a case or chassis in a tower shape (desktop) and the following parts

Motherboard

The motherboard is the "body" of the computer. Components directly attached to the motherboard include

• The Central Processing (CPU) performs most of the Calculations Which Enable a Computer to function, and is a sometimes referred as the “ bran” of the computer. It is usually cooled by a heat Sink and fan
  
• The Chipset mediates communication between the CPU and the other computer of the system, including main memory
  
• RAM stores all running Processes (applications) and the current running OS. RAM stands for Random Access Memory
  
• The BIOS includes boot Firmware and power management. The Basic Input Output System tasks are handled by operating system drivers
  
• Internal Buses connect the CPU to various internal Components and expansion cards for graphics and sound

Current

• The northbridge memory controller, for RAM and PCI Express
  
• PCI Express, for graphics
  
• PCI, for other expansion cards
  
• SATA, for disk drives

Obsolete

• ATA (superseded by SATA)
  
• AGP (superseded by PCI Express)
  
• VLB VESA Local Bus (superseded by AGP)


• ISA (expansion card slot format obsolete in PCs, but still used in industrial computers)

External Bus Controller

• USB
  
• FireWire
  
• eSATA

Processor

RAM

Random access memory (usually known by its acronym, RAM) is a form of computer data storage. Today it takes the form of integrated circuits that allows the stored data to be accessed in any order (i.e., at random). The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.

This contrasts with storage mechanisms such as tapes, magnetic discs and optical discs, which rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than the data transfer, and the retrieval time varies depending on the physical location of the next item.

The word RAM is mostly associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off. However, many other types of memory are RAM as well (i.e., Random Access Memory), including most types of ROM and a kind of flash memory called NOR-Flash.

power supply unit

A power supply unit (PSU) is the component that supplies power to a computer. More specifically, a power supply is typically designed to convert 100-120 V (North America and Japan) or 220-240 V (New Zealand, Europe, South America, Africa, Asia and Australia) AC power from the mains to usable low-voltage DC power for the internal components of the computer. Some power supplies have a switch to change between 230 V and 115 V. Other models have automatic sensors that switch input voltage automatically, or are able to accept any voltage between those limits.

The most common computer power supplies are built to conform with the ATX form factor. This enables different power supplies to be interchangeable with different components inside the computer. ATX power supplies also are designed to turn on and off using a signal from the motherboard, and provide support for modern functions such as the standby mode available in many computers. The most recent specification of the ATX standard PSU as of mid-2008 is version 2.31.

Hard Disk

A hard disk drive (often shortened as "hard disk" or "hard drive"), is a non- volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to a device distinct from its medium, such as a tape drive and its tape, or a floppy disk drive and its floppy disk. Early HDDs had removable media; however, an HDD today is typically a sealed unit (except for a filtered vent hole to equalize air pressure) with fixed media.

CD ROM

CD-ROM (an initialism of "compact disc read-only memory") is a pre-pressed compact disc that contains data accessible to, but not writable by, a computer. While the compact disc format was originally designed for music storage and playback, the 1985 “Yellow Book” standard developed by Sony and Philips adapted the format to hold any form of binary data.

CD-ROMs are popularly used to distribute computer software, including games and multimedia applications, though any data can be stored (up to the capacity limit of a disc). Some CDs hold both computer data and audio with the latter capable of being played on a CD player, while data (such as software or digital video) is only usable on a computer (such as PC CD-ROMs). These are called enhanced CDs.

Although many people use lowercase letters in this acronym, proper presentation is in all capital letters with a hyphen between CD and ROM. It was also suggested by some, especially soon after the technology was first released, that CD-ROM was an acronym for "Compact Disc read-only-media", or that it was a more "correct" definition. This was not the intention of the original team who developed the CD-ROM, and common acceptance of the "memory" definition is now almost universal. This is probably in no small part due to the widespread use of other "ROM" acronyms such as Flash-ROMs and EEPROMs where "memory" is usually the correct term.