December 2001 Introduction 8 – 3
8 Data Interfaces
8.1 Introduction
In addition to their Central Processing Unit (CPU), computer systems usually
include various peripheral devices.
A CPU is, for example:
n PC
n Control
Peripheral devices include:
n Printers
n Scanners
n External storage devices, such as floppy-disk drives and hard disks
n Other computer systems
A data interface makes it possible for the CPU and its peripheral devices to
communicate.
The interfaces, which consist of physical links between the computer system
and the peripherals, need a transmission line and appropriate software in order
to transfer data between the individual units.
Standard interfaces include:
n RS-232-C/V.24 or
n RS-422/V.11
The relationship between hardware and software, which fully defines an
interface, is illustrated by the following diagram:
The “hardware” in the diagram covers all the physical components, such as:
n Circuit construction
n Connection layout
n Electrical characteristics
The “software” is the operating software, which includes, for example, the
drivers for the output modules.
Software
Hardware
Software
Computer
Peripherals
e.g. PC,
control
e.g. printer,
external
memory
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