Introduction
Almost everything you do on the web — opening a website, logging into your bank account, submitting an online job application on teletalk.com.bd — runs on one fundamental idea: client-server architecture, and the language that clients and servers speak to each other is called HTTP (HyperText Transfer Protocol).
For BCS, Bank IT-officer and other government IT recruitment exams, this topic is a guaranteed scorer. Examiners love it because it produces crisp one-mark MCQs: Which port does HTTP use? What does the 404 status code mean? Is HTTP stateless or stateful? What is the full form of URL? If you understand the mechanism from first principles — not just memorised facts — you can answer any variation they throw at you. This lesson builds that understanding step by step.
Learning objectives
After studying this lesson you should be able to:
- Define client, server, host, and describe how a request-response cycle works.
- Distinguish the main architectural models: 2-tier, 3-tier, n-tier, and peer-to-peer.
- Explain what a protocol is and where HTTP sits in the TCP/IP model.
- Break down a URL into its components and read them correctly.
- Describe the full journey of a web request: DNS → TCP → HTTP → response → render.
- List and use the common HTTP methods (GET, POST, PUT, DELETE, etc.).
- Recall and classify HTTP status codes (1xx–5xx) and know the famous ones.
- Explain why HTTP is stateless, and how cookies and sessions add state.
- Compare HTTP vs HTTPS and describe the role of SSL/TLS, ports 80 and 443.
- Answer exam MCQs on ports, methods, status codes, and full forms with confidence.