Peripheral

Peripheral, in computer science, a term used for devices, such as disk drives, printers, modems, and joysticks, that are connected to a computer and are controlled by its microprocessor. Although peripheral often implies “additional but not essential,” many peripheral devices are critical elements of a fully functioning and useful computer system. Few people, for example, would argue that disk drives are nonessential, although computers can function without them. Keyboards, monitors, and mice are also strictly considered peripheral devices, but because they represent primary sources of input and output in most computer systems, they can be considered more as extensions of the system unit than as peripherals. See also Disk Drive; Input/Output Device; Joystick; Keyboard; Modem; Mouse.