Those devices which are not required or essential for a computer system to boot and run are called peripheral devices. A computer system has four categories of computer hardware among which mostly all I/O devices are peripheral devices. Though there are other devices which are both input and output devices and most of them are peripheral devices. Along with these external and storage devices are also peripherals when the system already has its default storage and memory units.
Peripheral devices help in better use of the computer system, but the computer system itself can run without them.
Examples: Mouse, Keyboard, Sound System etc.
Types of Peripheral Devices:
Base on installation there are two types of Peripheral Devices.
Internal Peripheral Devices:
Those peripheral devices which are installed or connected to the computer system internally are called Internal Peripheral Devices.
Examples: CD/DDV Rom, internal modem, interal sound cards etc.
External Peripheral Devices:
Those peripheral devices which are installed or connected to the computer system externally are called External Peripheral Devices.
Example: Keyboard, Mouse etc.
Based on function, there are three types of peripheral devices.
Input Peripheral Devices:
Those peripheral devices which are used to send data to computer system are called input peripheral devices.
Example: Microphone, Mouse etc.
Output Peripheral Devices:
Those peripheral devices which are used to get data from computer system are called output peripheral devices.
Example: Monitor, Printer etc.