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Main article: Personal computer hardware Hardware is a comprehensive term for all of the physical parts of a computer, as distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish tasks. The boundary between hardware and software is slightly blurry - firmware is software that is "built-in" to the hardware. Mass-market consumer computers use highly standardized components and so are simple for an end user to assemble into a working system. A typical desktop computer consists of a computer case which holds the power supply, motherboard, hard disk and often an optical disc drive. External devices such as a computer monitor or visual display unit, keyboard, and a pointing device are usually found in a personal computer. The motherboard connects all processor, memory and peripheral devices together. The RAM, graphics card and processor are mounted directly onto the motherboard. The central processing unit microprocessor chip plugs into a socket. Expansion memory plugs into memory sockets. Some motherboards have the video display adapter, sound and other peripherals integrated onto the motherboard, while others use expansion slots for graphics cards, network cards, or other I/O devices. The graphics card or sound card may employ a break out box to keep the analog parts away from the electromagnetic radiation inside the computer case. Disk drives for mass storage are connected to the mother board with a cable, and to the power supply through another cable. Usually disk drives are mounted in the same case as the motherboard; formerly, expansion chassis were made for additional disk storage. For really large amounts of data, a tape drive can be used or extra hard disks can be put together in an external case. The keyboard and the mouse are external devices plugged into the computer through connectors on an I/O panel on the back of the computer. The monitor is also connected to the I/O panel, either through an onboard port on the motherboard, or a port on the graphics card. The hardware capabilities of personal computers can sometimes be extended by the addition of expansion cards connected via an expansion bus. Some standard peripheral buses often used for adding expansion cards in personal computers as of 2005 are PCI, AGP (a high-speed PCI bus dedicated to graphics adapters), and PCI Express. Most personal computers as of 2005 have multiple physical PCI expansion slots. Many also include an AGP bus and expansion slot or a PCI Express bus and one or more expansion slots, but few PCs contain both buses. Computer case__ Main article: Computer case A stripped ATX case lying on its side. A computer case is the enclosure that contains the main components of a computer. Cases are usually constructed from steel or aluminum, although other materials such as wood and plastic have been used. Cases can come in many different sizes, or form factors. The size and shape of a computer case is usually determined by the form factor of the motherboard that it is designed to accommodate, since this is the largest and most central component of most computers. Consequently, personal computer form factors typically specify only the internal dimensions and layout of the case. Form factors for rack-mounted and blade servers may include precise external dimensions as well, since these cases must themselves fit in specific enclosures. Currently, the most popular form factor for desktop computers is ATX, although microATX and small form factors have become very popular for a variety of uses. Companies like Shuttle Inc. and AOpen have popularized small cases, for which FlexATX is the most common motherboard size. Power supply unit__ Main article: Power supply unit (computer) Computer power supply unit with top cover removed. The power supply unit converts general purpose electric current from the mains to direct current for the other components of the computer. The rated output capacity will be about 40% greater than the calculated system power consumption needs obtained by adding up all the system components. This protects against overloading the supply, and guards against performance degradation. Processor__ Main article: Central processing unit AMD Athlon 64 X2 CPU. The central processing unit, or CPU, is that part of a computer which executes software program instructions. In newer PCs the CPU is about a million transistors in one integrated circuit chip called the microprocessor. The microprocessor plugs into the motherboard. The chip generates so much heat that the PC builder is required to attach a special cooling device to its surface. Modern CPUs are equipped with a fan attached via heat sink. IBM PC compatible computers use an x86-compatible microprocessor. Intel, AMD, VIA Technologies or Transmeta manufacture them. Apple Macintosh computers were initially built with the Motorola 680x0 family of processors, then switched to the PowerPC series. In 2006 they switched to x86-compatible processors by Intel. Motherboard__ Main article: Motherboard A motherboard without processor, memory and extension cards, cables The motherboard, also referred to as system board or main board, is the primary circuit board within a personal computer. Other major system components plug directly onto or cable into the motherboard. A motherboard will contain a microprocessor, the CPU supporting circuitry (mostly integrated circuits) that provide the interface between memory and input/output peripheral circuits, main memory, and facilities for initial setup of the computer immediately after power-on (often called boot firmware or, in IBM PC compatible computers, a BIOS). In many portable and embedded personal computers, the motherboard houses nearly all of the PC's core components. Often a motherboard will also contain one or more peripheral buses and physical connectors for expansion purposes. Sometimes a secondary daughter board is connected to the motherboard to provide further expandability or to satisfy space constraints. Main memory__ Main article: Primary storage 1GB DDR SDRAM PC-3200 module A PC's main memory is a fast storage device that is directly accessible by the CPU, and is used to store the currently executing program and immediately needed data. PCs use semiconductor random access memory (RAM) of various kinds such as DRAM, SDRAM or SRAM as their primary storage. Which exact kind depends on cost/performance issues at any particular time. Main memory is much faster than mass storage devices like hard disks or optical discs, but is usually volatile, meaning it does not retain its contents (instructions or data) in the absence of power, and is much more expensive for a given capacity than is most mass storage. Main memory is generally not suitable for long-term or archival data storage. Hard disk__ Main article: Hard disk drive A Western Digital 250 GB hard disk drive. Mass storage devices store programs and data even when the power is off; they do require power to perform read and write functions during usage. Although flash memory has dropped in cost, the prevailing form of mass storage in personal computers is still the hard disk. The disk drives use a sealed head/disk assembly (HDA) which was first introduced by IBM's "Winchester" disk system. The use of a sealed assembly allowed the use of positive air pressure to drive out particles from the surface of the disk, which improves reliability. If the mass storage controller provides for expandability, a PC may also be upgraded by the addition of extra hard disk or optical disc drives. For example, BD-ROMs, DVD-RWs, and various optical disc recorders may all be added by the user to certain PCs. Standard internal storage device connection interfaces are PATA, Serial ATA, and SCSI. Solid state drives or SSD has begun replacing traditional mechanical hard drives. Visual display unit__ Main article: Visual display unit A visual display unit, or "computer monitor", or just display, is a piece of electrical equipment, usually separate from the computer case, which displays visual images without producing a permanent computer record. A display device is usually either a CRT or some form of flat panel such as a TFT LCD. The display unit houses the circuitry that generates its picture from signals sent from the computer. Within the computer, either integral to the motherboard, or plugged into it as an Expansion card, there is pre-processing circuitry to convert the microprocessor's output data to a format compatible with the display unit's circuitry. The images from computer monitors originally contained only text, but as graphical user interfaces emerged and became common, they began to display more images and multimedia content. The term "monitor" is also used, particularly by technicians in broadcasting television, where a picture of the broadcast data is displayed to a highly standardized reference monitor for confidence checking purposes. Video card__ Main article: Video card ATI Radeon video card The video card—otherwise called a graphics card, graphics adapter or video adapter—processes the graphics output from the motherboard and transmits it to the display. It is an essential part of modern multimedia computing. On older models, and today on budget models, graphics circuitry may be integrated with the motherboard, but for modern and flexible machines, they are connected by the PCI, AGP, or PCI Express interface. When the IBM PC was introduced, most existing business-oriented personal computers used text-only display adapters and had no graphics capability. Home computers at that time had graphics compatible with television signals, but with low resolution by modern standards owing to the limited memory available to the eight-bit processors available at the time. Keyboard__ Main article: Keyboard (computing) A "Model M" IBM computer keyboard from the early 1980s. Commonly called the "Clicky Keyboard" due to its buckling spring key spring design, which gives the keyboard its iconic 'Click' sound with each keystroke. In computing, a keyboard is an arrangement of buttons that each correspond to a function, letter, or number. They are the primary devices of inputting text. In most cases, they contain an array of keys specifically organized with the corresponding letters, numbers, and functions printed or engraved on the button. They are generally designed around an operators language, and many different versions for different languages exist. In English, the most common layout is the QWERTY layout, which was originally used in typewriters. They have evolved over time, and have been modified for use in computers with the addition of function keys, number keys, arrow keys, and OS specific keys. Often, specific functions can be achieved by pressing multiple keys at once or in succession, such as inputting characters with accents or opening a task manager. Programs use keyboard shortcuts very differently and all use different keyboard shortcuts for different program specific operations, such as refreshing a web page in a web browser or selecting all text in a word processor. Mouse__ Main article: Mouse (computing) Computer mice built between 1986 and 2007 A Mouse on a computer is a small, slideable device that users hold and slide around to point at, click on, and sometimes drag objects on screen in a graphical user interface using a pointer on screen. Almost all Personal Computers have mice. It may be plugged into a computer's rear mouse socket, or as a USB device, or, more recently, may be connected wirelessly via a USB antenna or Bluetooth antenna. In the past, they had a single button that users could press down on the device to "click" on whatever the pointer on the screen was hovering over. Now, however, many Mice have two or three buttons(possibly more); a "right click" function button on the mouse, which performs a secondary action on a selected object, and a scroll wheel, which users can rotate using their fingers to "scroll" up or down. The scroll wheel can also be pressed down, and therefore be used as a third button. Some mouse wheels may be tilted from side to side to allow sideways scrolling. Different programs make use of these functions differently, and may scroll horizontally by default with the scroll wheel, open different menus with different buttons, among others. These functions may be user defined through software utilities. Mice traditionally detected movement and communicated with the computer with an internal "mouse ball"; and used optical encoders to detect rotation of the ball and tell the computer where the mouse has moved. However, these systems were subject to low durability, accuracy and required internal cleaning. Modern mice use optical technology to directly trace movement of the surface under the mouse and are much more accurate, durable and almost maintenance free. They work on a wider variety of surfaces and can even operate on walls, ceilings or other non-horizontal surfaces. Other components__ Proper ergonomic design of personal computer workplace is necessary to prevent repetitive strain injuries, which can develop over time and can lead to long-term disability.[54] Mass storage All computers require either fixed or removable storage for their operating system, programs and user generated material. Formerly the 5¼ inch and 3½ inch floppy drive were the principal forms of removable storage for backup of user files and distribution of software. As memory sizes increased, the capacity of the floppy did not keep pace; the Zip drive and other higher-capacity removable media were introduced but never became as prevalent as the floppy drive. By the late 1990s the optical drive, in CD and later DVD and Blu-ray Disc, became the main method for software distribution, and writeable media provided backup and file interchange. Floppy drives have become uncommon in desktop personal computers since about 2000, and were dropped from many laptop systems even earlier.[note 1] Early home computers used compact audio cassettes for file storage; these were at the time a very low cost storage solution, but were displaced by floppy disk drives when manufacturing costs dropped, by the mid-1980s. A second generation of tape recorders was provided when Videocassette recorders were pressed into service as backup media for larger disk drives. All these systems were less reliable and slower than purpose-built magnetic tape drives. Such tape drives were uncommon in consumer-type personal computers but were a necessity in business or industrial use. Interchange of data such as photographs from digital cameras is greatly expedited by installation of a card reader, which often is compatible with several forms of flash memory. It is usually faster and more convenient to move large amounts of data by removing the card from the mobile device, instead of communicating with the mobile device through a USB interface. A USB flash drive today performs much of the data transfer and backup functions formerly done with floppy drives, Zip disks and other devices. Main-stream current operating systems for personal computers provide standard support for flash drives, allowing interchange even between computers using different processors and operating systems. The compact size and lack of moving parts or dirt-sensitive media, combined with low cost for high capacity, have made flash drives a popular and useful accessory for any personal computer user. The operating system (e.g.: Microsoft Windows, Mac OS, Linux or many others) can be located on any storage, but typically it is on a hard disks. A Live CD is the running of an OS directly from a CD. While this is slow compared to storing the OS on a hard drive, it is typically used for installation of operating systems, demonstrations, system recovery, or other special purposes. Large flash memory is currently more expensive than hard drives of similar size (as of mid-2008) but are starting to appear in laptop computers because of their low weight, small size and low power requirements. Computer communications Internal modem card Modem Network adapter card Router Common peripherals and adapter cards Headset Joystick Microphone Printer Scanner Sound adapter card as a separate card rather than located on the motherboard Speakers Webcam |
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