The Internet (Cambridge (CIE) A Level Computer Science) : Revision Note

Internet vs WWW

What is the Internet?

• The Internet is a global network of networks (Interconnected Network)

• The Internet is the most well-known Wide Area Network (WAN)

• The Internet is the infrastructure used to provide connectivity to the World Wide Web (WWW)

• Uses protocols like TCP/IP to transfer data between devices and networks

What is the World Wide Web (WWW)?

• The world wide web, or simply the web, is a collection of websites and web pages that are accessed using the Internet

• It was created in 1989 by Tim Berners-Lee, who envisioned it as a way to share and access information on a global scale

• The web consists of interconnected documents and multimedia files that are stored on web servers around the world

• Web pages are accessed using a web browser, which communicates with web servers to retrieve and display the content

• Uses protocols like HTTP and HTTPS to request and deliver web content

Internet hardware

Modem

• Modem stands for modulator-demodulator

• Converts digital signals from a computer into analogue signals to send over telephone or cable lines

• Also converts analogue signals back into digital so the computer can understand them

• Allows devices to connect to the internet through technologies like:

  • DSL

  • Cable

  • Dial-up

• Used to send and receive data over long distances via traditional communication lines

Public Switched Telephone Network (PSTN)

• Developed soon after the invention of the telephone in the late 1800s

• Originally built to handle voice communication over copper wires

• As the demand for other forms of communication grew, the PSTN was adapted to enable internet access

• Used to connect computers/devices and LANs between towns and cities

• Traditional copper telephone lines are being slowly replaced with fibre optic cables

  • Fibre gives access to higher bandwidth and faster data transfer speeds

Dedicated lines

• Dedicated lines (e.g. T1, T3, and fibre-optic) provide exclusive, high-speed connections between two points

• Unlike the PSTN, these connections are always active and not shared with other users

  • Faster and more reliable

  • Ideal for businesses and organisations needing consistent, high-bandwidth internet

  • Better for activities like video conferencing, cloud computing, and large file transfers

Cellular networks

• Provide wireless communication for mobile phones and other portable devices

• The network is made up of cells, each served by a cell tower (base station)

• Devices connect to the nearest tower to send and receive signals

• As a user moves, their device automatically switches to the next closest tower (handover)

• Used for voice calls, text messaging, and mobile data (internet access)

• Support different generations of mobile technology:

  • 2G – Basic calls and texts

  • 3G – Mobile internet and video calling

  • 4G – Fast internet browsing and streaming

  • 5G – Very high-speed internet, low latency (great for gaming and real-time apps)