January 2012 9.1 Introduction 1759
9 Data Interfaces
9.1 Introduction
In addition to their Central Processing Unit (CPU), computer systems usually 
include various peripheral devices.
A CPU is, for example:
 PC
 Control
Peripheral devices include:
 Printers
 Scanners
 External storage devices, such as hard disks, floppy-disk drives or USB 
memory sticks.
 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:
 Ethernet
 USB 1.1
 RS-232-C/V.24
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
 Circuit design
 Pin Layout
 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