memory is generally not suitable for long-term or archival data storage.
Hard disk[edit]
Main article: 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 drive.
If the mass storage controller provides additional ports 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 (SSDs) are a much faster replacement for traditional mechanical hard disk drives, but are also more expensive in terms of cost per gigabyte.
Visual display unit[edit]
Main article: Visual display unit
A visual display unit, computer monitor or just display, is a piece of electrical equipment, usually separate from the computer case, which displays visual imageswithout producing a permanent computer record. A display device is usually either a CRT or some form of flat panel such as a TFT LCD. Multi-monitor setups are also quite common.
The display unit houses an electronic circuitry that generates its picture from signals received 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 standardizedreference monitor for confidence checking purposes.
Video card[edit]
Main article: 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-enriched 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[edit]
Main article: Keyboard (computing)
A keyboard is an arrangement of buttons that each correspond to a function, letter, or number. They are the primary devices used for 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 keys specific to an operating system. 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[edit]
Main article: Mouse (computing)
A computer mouse is a small handheld device that users hold and slide across a flat surface, pointing at various elements of a graphical user interface with an on-screen cursor, and selecting and moving objects using the mouse buttons. Almost all modern personal computers include a mouse; it may be plugged into a computer's rear mouse socket, or as a USB device, or, more recently, may be connected wirelessly via an USB dongle or Bluetooth link.
In the past, mice had a single button that users could press down on the device to "click" on whatever the pointer on the screen was hovering over. Modern mice have two, three or more buttons, providing 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, etc. These functions may be also user-defined through software utilities.
Mice traditionally detected movement and communicated with the computer with an internal "mouse ball", and used opticalencoders 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.
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