A single computer is powerful; millions of connected computers changed the world. A computer network is two or more devices linked together to share data and resources. This unit is about how they connect and communicate — and it starts with why networks exist and how the Internet came to be.
1What is a network — and why
A computer network is a collection of computers and devices connected together so they can communicate and share — files, an internet connection, printers, and more.
| Advantages | Disadvantages |
|---|---|
| Resource sharing (files, printers, internet) | Setup and maintenance cost |
| Fast communication (email, chat, calls) | Security risks (hacking, viruses spread) |
| Centralised data & backups | If the server/network fails, many users are affected |
| Cost saving (shared hardware & software) | Needs technical skill to manage |
- A network is two or more connected devices that communicate and share resources.
- Advantages: resource sharing, fast communication, centralised data, cost saving.
- Disadvantages: cost, security risks, dependence on the network/server, management effort.
2From ARPANET to the Internet
The Internet didn't appear overnight — it grew from a research project:
- ARPANET (1969) was the first network, funded by the US Dept of Defense — the Internet's ancestor.
- NSFNET expanded networking to universities and research centres in the 1980s.
- The Internet is the global 'network of networks', joined by the common TCP/IP protocols.
- The Internet (infrastructure) is not the same as the World Wide Web (websites running on it).
3Switching: circuit vs packet
How does data actually get from sender to receiver across a network? Through switching — and there are two main techniques:
| Circuit Switching | Packet Switching | |
|---|---|---|
| How it works | A dedicated physical path is set up for the whole conversation | Data is split into small packets that travel independently and are reassembled at the end |
| Classic example | The old telephone network | The Internet |
| Efficiency | Path is reserved even when idle — can waste capacity | Shares the network efficiently; packets take the best available route |
- Switching moves data from sender to receiver across a network.
- Circuit switching reserves a dedicated path for the whole call (e.g. old telephones).
- Packet switching splits data into independent packets, reassembled at the destination (the Internet) — efficient and robust.
★ Practical: think it through
Answer briefly:
- List two advantages and two disadvantages of networking a school's computers.
- Put these in order: NSFNET, the Internet, ARPANET.
- Explain one reason packet switching is more robust than circuit switching.
- In one line, state the difference between the Internet and the World Wide Web.
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