🌐 CIE IGCSE Computer Science – The Internet and the World Wide Web
This topic explains the structure of the internet, how the world wide web (WWW) works, URLs, HTTP/HTTPS, web browsers, web page retrieval, and cookies.
1️⃣ Internet vs World Wide Web
| Feature | Internet | World Wide Web (WWW) |
|---|---|---|
| Definition | Global network of interconnected computers and devices | Collection of websites and web pages accessed via the internet |
| Function | Provides infrastructure for communication | Uses the internet to deliver content (websites) |
| Example | Routers, IP addresses, network cables | Google, Wikipedia, YouTube |
Key point: The internet is the hardware/network infrastructure, while the WWW is a service that runs on it.
2️⃣ Uniform Resource Locator (URL)
Definition:
A URL is a text-based address used to locate a specific web page on the internet.
Structure:
https://www.example.com/folder/page.html
| | | |
|protocol|domain |path/file|
- Protocol:
http://orhttps:// - Domain name:
www.example.com– human-readable address - Path & filename:
/folder/page.html– location of the file on the server
Example:
https://www.wikipedia.org/wiki/Physics
- Protocol: HTTPS
- Domain: wikipedia.org
- Path/file:
/wiki/Physics
3️⃣ HTTP and HTTPS
| Feature | HTTP | HTTPS |
|---|---|---|
| Stands for | Hypertext Transfer Protocol | Hypertext Transfer Protocol Secure |
| Purpose | Transfers web pages from server to client | Transfers web pages securely (encrypted) |
| Security | Data is sent as plain text | Data is encrypted using SSL/TLS |
| Use | Public websites | Banking, login pages, online shopping |
Key point: HTTPS protects sensitive information like passwords, credit card numbers.
4️⃣ Web Browser
Definition:
Software that allows a user to access, retrieve, and display web pages.
Main Purpose:
- Render HTML and display web content.
Common Functions:
- Storing bookmarks/favourites
- Recording user history
- Allowing multiple tabs
- Storing cookies
- Navigation tools (Back/Forward buttons)
- Address bar for URLs
Examples:
- Google Chrome, Mozilla Firefox, Microsoft Edge, Safari
5️⃣ How Web Pages Are Located, Retrieved, and Displayed
Step-by-Step Process:
- User enters URL in browser’s address bar.
- Domain Name System (DNS) converts the domain name to an IP address of the web server.
- Browser sends HTTP/HTTPS request to the web server at that IP address.
- Web server locates HTML file (and other resources: CSS, images, scripts).
- Server sends response (HTML, CSS, JavaScript) back to browser.
- Browser renders web page using HTML and displays it on the device.
Key Roles:
| Component | Role |
|---|---|
| Web browser | Sends requests, renders HTML, displays pages |
| DNS | Converts domain name → IP address |
| Web server | Stores and serves web pages/files |
| HTML | Language used to structure web page content |
6️⃣ Cookies
Definition:
Small files stored on a user’s device by a web browser containing information about the user’s interaction with a website.
Types of Cookies:
| Type | Duration | Purpose |
|---|---|---|
| Session cookies | Temporary, deleted when browser closes | Track user session, e.g., online shopping cart |
| Persistent cookies | Stored on device for set time | Save login credentials, preferences, settings |
Uses of Cookies:
- Save personal details for forms
- Track user preferences (language, theme)
- Hold items in online shopping carts
- Store login credentials
Security note: Cookies are not programs, but can be used to track online activity.
🧠 Key Terms
| Term | Definition |
|---|---|
| Internet | Global network infrastructure connecting computers |
| World Wide Web | Collection of web pages accessed via the internet |
| URL | Text-based address to locate a web page |
| HTTP | Protocol for transferring web pages (not encrypted) |
| HTTPS | Secure protocol using encryption |
| Web browser | Software to access, retrieve, and display web pages |
| DNS | Converts domain names into IP addresses |
| Web server | Computer that stores and serves web pages |
| HTML | Language to structure web content |
| Cookies | Files storing user information and preferences |
📝 Exam Tips
- Always distinguish internet vs WWW – infrastructure vs content.
- When describing how a web page is retrieved, mention:
- Browser → DNS → IP address → Web server → HTML → Render.
- Explain HTTP vs HTTPS in terms of security.
- Include examples for cookies (shopping carts, login credentials).
- Use diagrams where possible for browser-DNS-server interaction.
- Mention both session and persistent cookies and their purpose.
⭐ Quick Summary
- Internet: network infrastructure
- WWW: websites/web pages accessed via internet
- URL: address of web page (protocol + domain + path/file)
- HTTP: transfers pages; HTTPS: secure/encrypted
- Web browser: retrieves, renders, displays pages; stores cookies, history, bookmarks
- Cookies: store user info; session (temporary) or persistent (long-term)