Introduction
A computer network is a collection of two or more computing devices (computers, servers, phones, printers, sensors) connected by communication links so they can exchange data and share resources. Almost every modern service — the internet, mobile banking, government e-services, ATMs, office LANs — runs on networks. For BCS, Bank IT-officer and other government IT exams, this chapter is high-yield: questions on the definition of a network, the difference between LAN/MAN/WAN, the five physical topologies, and simple cable-count / performance calculations appear almost every year. This lesson builds the ideas from first principles so you can answer any variation of these questions, not just memorized facts.
Learning objectives
After studying this lesson you should be able to:
- Define a computer network and state its goals and benefits.
- Distinguish the criteria of an effective network: performance, reliability, security.
- Classify networks by scale: PAN, LAN, MAN, WAN (and CAN).
- Explain transmission modes (simplex, half-duplex, full-duplex) and connection types (point-to-point, multipoint).
- Define topology and describe the five basic physical topologies: bus, star, ring, mesh, tree, plus hybrid.
- Calculate the number of links, ports and I/O for a mesh, and reason about fault tolerance and cost.
- Compare topologies on cost, reliability, scalability and troubleshooting.
- Avoid the common exam traps (physical vs logical topology, cable counts, single point of failure).