A computer system may consist of several devices. Every device has its own functionality. We need these devices to work properly with computer. We can divide these devices into following types.

Input devices: An input device is used to provide data to computer for processing or storing. There are different types of input devices. Keyboard, mouse, scanner, light pen and barcode reader and card reader are the examples. All input devices are connected with the CPU. Different signals are generated from these devices which are then sent to CPU....

A “peripheral device” or “computer device” is a hardware component that is attached to a computer in order to expand its abilities and performing additional features. Computers are able to interact with its external world using the peripherals as mice, monitors, plotters, keyboards, and printers.

Peripheral means “additional but not essential”, so peripherals are not part of the essential computer as are the processor, and the memory. Some peripherals are mounted in the same case with the main part of the computer as are the hard disk drive or CD-ROM drive. If a peripheral device is disconnected, the computer will still be able to work. Other peripherals are outside the computer case, such as the printer and image scanner, attached by a wired or wireless connection....