5 -14 Beyond Level E - Computer Systems

In this section, we will look at the benefits of connecting computers together
This section will be concerned with:

Computer Networks

The Advantages of Networks

and

Modems

Introduction

When we connect computers together, we form a computer network. The smallest network would consist of only 2 connected computers. The largest network would consist of millions of computers all over the world connected together -like the INTERNET. There are two main types of networks:-

Local Area Network (LAN)

and

Wide Area Network (WAN)

Local Area Networks

A local area network consists of computers connected together in a small geographical area such a in an office or in a school.

The parts of a network are as follows:-

computers or stations - the computer systems which are connected together
cables - to connect the computers or stations together
a file server - to control the operation of the network and provide each station with somewhere to store and load files
a printer server - to allow each station to print over the network

Here is an image of a LAN:-

Wide Area Networks

When we connect together LANs which are in different locations, for example in different parts of the same town or in different parts of the country or even in different parts of the world, we form a Wide Area Network. WANS connect computers in different geographical areas.

In order to do this, we need to make uses of the telephone lines and a special device called a MODEM.

To form a WAN, one local area network (or LAN) is connected to a modem which is then connected to the telephone lines. At the other end, the same thing is done, the LAN is connected to a modem and the modem is connected to the telephone lines.

The two local area networks can then communicate because computer signals from one local area network are passed by the modem, down the telephone lines to the modem at the other end which passes the computer signals its local area network

Using a WAN we can make use of data and facilities on computers many miles away.

The Advantages of Networks

Here are some of the advantages of an office or school using a network instead of stand alone computers:-

large capacity hard disk drives can be shared
printers can be shared
files which everyone uses can be shared
people can communicate using electronic mail

Modems

The word MODEM stands for MODulator DEModulator. It is a piece of hardware which allows computers to communicate along telephone lines. It converts computer signals (digital) from a computer to acoustic or sound signals (analogue) which are sent down the telephone line. At the receiving end, the modem takes the acoustic or analogue signals and converts them to computer or digital signals which are then passed to the receiving computer.

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