Overview

Computers operate on many kinds of devices. General types include storage devices (disks, tapes), transmission devices (network cards, modems), andhuman-interface devices (screen, keyboard, mouse). Other devices are more specialized. A device communicates with a computer system by sending signals over a cable or even through the air.

The device communicates with the machine via a connection point termed aport (for example, a serial port). If one or more devices use a common set of wires, the connection is called a bus.In other terms, a bus is a set of wires and a rigidly defined protocol that specifies a set of messages that can be sent on the wires.