Overview

Computer peripherals are devices or equipment added to the basic processor and main memory to facilitate human-machine interface and permit the computer to carry out control functions or perform useful applications. Certain peripherals active in most computer operations such as hard-disk, diskette, and CD-ROM drives are mounted within the computer case for user convenience, while other peripherals such as the monitor, keyboard, and mouse are connected by cable or infrared link to the computer to permit their positions to be personalized on the desktop for user comfort. Other computer peripherals such as printers, scanners, and backup drives with cable connections can be located away from the computer in positions that will be convenient for their effective use.

The microprocessor, the most expensive and critical component in any personal computer, is the "engine" that determines the speed and versatility of the system, and it also dictates the operating system and applications software that can be used. Computers are sold with a basic main memory, but it can be supplemented if needed with add-in memory on plug-in daughter cards, which themselves can be considered as peripherals.

Hard-disk drives for personal computers for sale as retail products have now exceeded capacities of 16 MB for a 3.5-in (90-mm) drive, and drives have matched the rate of progress in IC chips, increasing storage density at the rate of about 60 percent annually. Recently drives for subnotebook computers with diameters of 1 in (25 mm) and capacities of 340 MB have been introduced, 1.5...