Introduction to Computer Networks – JSS1 Digital Technologies Lesson Note (Third Term)

A computer network is two or more computers connected together so that they can communicate and share files, hardware and information.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define a computer network.
2. State three reasons for connecting computers.
3. Name and describe LAN, MAN and WAN.
4. Give an example of each type of network.
5. Identify networks used in daily life.

What is a computer network?

A computer network is a group of computers and devices linked together to share data and resources.

• Standalone computer: a computer that is not connected to any other. You can type and play games on it.
• Limit of a standalone computer: it cannot send a message to a friend’s computer or print on a printer in another room.
• Networked computer: a computer linked to others, so it can talk to them and share things.

Why do we connect computers in a network?

We connect computers to share files, share hardware and communicate.

1. To share files: you can send a photo or document from your laptop to your brother’s tablet without a flash drive.
2. To share hardware: ten computers can use one printer instead of ten printers. This saves money.
3. To communicate: networks let us send emails and chat instantly.

What do we need to build a network?

A network needs at least two computers, a way to link them, and a device to direct data.

• Computers or devices: laptops, desktops, phones, tablets and printers that join the network.
• Cables or Wi-Fi: the link that carries data. Ethernet cables are wired, while Wi-Fi is wireless.
• Switch or router: a device that directs data between the connected devices. A router also links a network to the Internet.

What are the types of computer networks?

There are three main types of computer network, grouped by the area they cover: LAN, MAN and WAN.

What is a LAN?

A LAN (Local Area Network) is a network that covers a small area such as a room, a house or a school computer lab.

• Users: you, your teachers and your family.
• Connection: Ethernet cables or Wi-Fi.
• Speed: usually fast, because the computers are close together.
• Example: all the computers in your school lab connected to the teacher’s main computer.
• Example: your home Wi-Fi connecting your phone, TV and laptop.

What is a MAN?

A MAN (Metropolitan Area Network) is a network that connects several LANs across a whole city.

• Meaning of “metropolis”: a big city.
• Size: bigger than a LAN but smaller than a WAN.
• Example: a bank with five branches in Lagos or Abuja that connects all its computers to share customer information.

What is a WAN?

A WAN (Wide Area Network) is a network that covers a very large area such as a country, a continent or the whole world.

• Size: the largest type of network.
• Example: the Internet is the most famous WAN. It connects billions of computers around the world using satellites and undersea cables.

How do LAN, MAN and WAN compare?

What are examples of networks in daily life?

We use networks every day, often without noticing.

• The ATM machine: it is part of a WAN. It contacts the bank’s main computer far away to check your account balance.
• Multiplayer gaming: two friends in the same room playing together on two phones are using a LAN.
• School results: a teacher enters scores on one computer and the Principal sees them on another in his office. This uses the school LAN.
• Social media: when you post a photo on Instagram and your auntie in the village sees it, you are using the WAN (the Internet).

What are the advantages and disadvantages of networks?

Networks save time and money, but they cost money to set up and need protection.

Advantages

• Saves money: devices such as printers are shared.
• Saves time: files move quickly between computers.
• Easy communication: users send messages and emails at once.

Disadvantages

• Set-up cost: cables, routers and switches must be bought.
• Security risk: unauthorised people may try to reach private files.
• Spread of viruses: a virus on one computer can pass to others on the network.

Evaluation

1. What is a computer network?
2. State three reasons for connecting computers in a network.
3. Write the full meaning of LAN, MAN and WAN.
4. Which type of network is the Internet?
5. An ATM contacts a bank’s main computer far away. Which type of network does it use?

Assignment

1. Look at your school computer lab. State how the computers are connected and whether it is a LAN or a WAN.
2. Give one reason why a school should have a computer network.