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Unit 4: Secondary Storage Devices
4.2 Input/Output Device Notes
To be useful, a computer system needs to communicate with its external environment (its
users). The input-output devices (abbreviated UO devices) provide this capability to a computer
system (See Figure 4.5). They are know as peripheral devices because they surround a computers
CPU and memory. Input devices are used. enter data from outside world into primary
storage, and output devices supply the results of processing from primary storage to users.
A wide variety of I/O devices is now available. For a particular application, one type may
be more suitable than another type. Some devices are used for both input and output
function.
Figure 4.5: Illustrating the Role of I/O Devices in a Computer System
It is important to note that the speed of I/O devices is very slow as compared to the speed
of primary storage and CPU. This is because their speed in most cases depends on the
movement of mechanical parts, and the pote7_jriLl for improvement in speed of such parts
is limited. It is, therefore, difficult to produce I/O devices that can match processor and
memory speeds, and there is a constant demand for faster and faster I/O devices.
4.2.1 Input Devices
An input device is an electromechanical device that accepts data from outside world and
translates them into a computer can interpret. Several input devices are available today. They
can be broadly classified into following categories:
Keyboard devices
Point-and-draw devices
Data scanning devices
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