To be useful-output devices (abb needs to communicate with external environment (its user). Input-output (abbreviated I/O devices) provide this capability to computer system. They are also known as peripheral devices because they surround a computer CPU and memory. Input devices enter data from outside world into primary storage, and output devices supply the results of precessing from primary storage to users. Today, many types of I/O devices are available . For an application, one type be more suitable than another type. Some I/O devices perform both input and output functions. This chapter familiarizes the readers with commonly used types of I/O devices.
Note that the speed of I/O devices is very slow as compared to that of primary storage and CPU. This is because their in most cases depends on movement of mechanical parts, and the potential for improvement in speed of such parts is limited. It is there, fore, difficult to produce I/O devices that can match processor and memory speeds, and there constant demand for faster I/O devices.