I/O module

Q. What do you mean by I/O module? What are the two basic functions of an I/O module?
Ans: An I/O module is not simply a set of mechanical connectors that wire a device into the system bus. Rather, the I/O module contains logic for performing a communication function between the peripheral and the bus.

The I/O module has two major functions. These are given below:

• Interface to the processor and memory via the system bus or central switch.


• Interface to one or more peripheral devices by tailored data links.

Q. Explain three broad classifications of external or peripheral devices.

Ans: External devices are broadly classified into three categories:

• Human readable: Suitable for communicating with the computer user. Examples of human – readable devices are video display terminals (VDTs) and printers.


• Machine readable: Suitable for communicating with equipment. Example of machine readable devices is magnetic disk and tape systems, and sensor and actuators, such as are used in a robotics application.


• Communication: Suitable for communicating with remote devices. Communication devices allow a computer to exchange data with a remote device, which may be a human – readable device, such as a terminal, a machine – readable device or even another computer.