Networks

NETWORKS
A computer network is a collection of computers that have been linked together so that they can communicate with each other. This enables them to share both hardware, software and data.
LOCAL AREA NETWORK
A Personal Computer (PC) at home is often connected to a printer, a modem and maybe even a scanner. All the software needed to run the machine are installed directly onto its hard disk. This is known as a 'stand-alone' machine and is extremely versatile when only one person at a time wants to use the machine or 'peripherals'.

In an office or other large public building such as a school, there are usually many computers in constant use throughout the day. The problems with having many stand alone machines are:

Users cannot easily share information
Every computer needs to be connectedto a printer
Software licences for every machine are expensive
People forget to back up the files they are working on.

With these problems in mind, it was realised at an early stage that connecting these computers together would overcome many of the disadvantages mentioned above. This connection is known as a Computer Network.

When PCs close to one another in a single office or building are joined by a cable, a network is formed known as a Local Area Network (LAN).

Once the computers are connected together into a LAN, many people (users) can share and use the same resources at the same time. They can share files, software, hard disks and peripherals such as a printer or CD-ROM. Users can also use the LAN to communicate with each other by e-mail. Data can be transmitted very quickly between networked computers.

How can you tell whether a computer is networked to other computers?

Usually a networked computer will allow you to send messages to a friend who is working on another computer.
You will probably see messages telling you that you are entering a networked system when you logon.
Sometimes you will see shared resources such as files and software.
Sometimes you will have a choice of more than one printer to send your printouts to
If you have a file server you are also likely to have some space on the server's disk reserved for you to save your work.

WIDE AREA NETWORK
Many modern companies have offices, shops or factories in various locations around the country, and for large corporations, across the world. Even though staff work in different places, they often need to be able to access the same information no matter where they are.

It would not be possible to connect computers in different buildings together using the LAN cables. Imagine how many roads would need to be dug up to lay cables between every single building.

Computers on LANs in one building can be connected to computers on LANs in another building usually through the telephone system, often using a modem. They can also be connected via fibre optic cables, microwave links or satellite.

Workstations and servers:
People connect to the network by using a computer such as a Desktop PC. This machine is often called a 'workstation' or a 'terminal'.
Workstations connect to Servers. These machines can be identical to a Desktop PC but they have a special role to play. They exist to 'serve' and store files to and from the workstations, hence the word, 'Server'. They are often more powerful than a standard PC because they need to store a vast amount of data.

Advantages of Networks:

• Programs can be shared- software packages can be installed onto the file server and accessed by all individual workstations at the same time. This reduces cost, maintenance and makes upgrades easier.
• A user can access any software from any station.
• Data can be shared by all users at the same time. Many people can access or update the information held on a database at the same time. Thus information is up to date and accurate.
• Users can communicate with others on the network by sending messages and sharing files.
• Individual workstations do not need a printer, one high quality printer can now be shared by everyone, thus cutting costs.
• Networks provide security. A user must have the correct Password and User ID in order to be able to access the information on the network.
• Private areas on the network can be set up that allows each user to store their personal files. The only other person who can access these files is the 'system administrator' who looks after the network.

Disadvantages of Networks:

• Networks can be expensive to set up. They often involve taking up floors and ceilings to lay hundreds of metres of cables.
• The File Server needs to be a powerful computer, which often means that it is expensive.
• Networks are vulnerable to security problems. Hackers, disgruntled employees or even competitors might try to break into the system to read or damage crucial information. Much effort is spent preventing unauthorised access to data and software.
• If the main File Server breaks down, then the whole system becomes useless and no-one can carry on working.
• Because networks are often complicated, they need expensive expert staff to look after them.
• As the number of users increase on the network, the performance of the system can be affected and things start to slow down.

On the whole, the advantages of networks outweigh the disadvantages. This is why they are so commonly found in schools, offices and factories. Even home users are starting to use networks to connect PCs around the house.