Topic 5: The Internet and its Uses — Part 1

01 Internet vs World Wide Web

The Internet

A global network of interconnected computers and devices that provides the physical and technical infrastructure for data transmission.

The World Wide Web (WWW)

A collection of websites and web pages accessed via the internet using a web browser.

The WWW is just one service that runs on the internet, alongside others like email and messaging.

02 URLs and protocols

A URL is a text-based address used to access files on the internet. It typically consists of three parts:

• Protocol: rules for data transmission (e.g. https).
• Domain name: the human-readable address of the website (e.g. www.example.com).
• Web page / file name: the specific page or file requested (e.g. /index.html).

HTTP

Used for transferring web pages.

HTTPS

The secure version of HTTP; it adds encryption using SSL/TLS to protect data from interception.

03 Web browsers and page retrieval

Purpose

The primary purpose of a web browser is to render HTML and display web pages to the user.

Functions

Storing bookmarks, recording user history, managing multiple tabs, storing cookies, providing navigation tools (back/forward), and an address bar.

How a web page is retrieved

1. The user enters a URL into the browser.
2. The browser interprets the domain name and contacts a Domain Name Server (DNS) to find the web server's IP address.
3. The browser sends a request to the web server using that IP address.
4. The server processes the request and sends the resources (HTML, CSS, images) back to the browser.
5. The browser interprets the HTML to render and display the page.

04 Cookies

Definition

Small text files stored on a user's device by a website to save information between visits.

Uses

Saving personal details, tracking preferences, holding items in shopping carts, and storing login status.

Session cookies

Temporary files deleted when the browser is closed.

Persistent cookies

Remain on the device for a set period until they expire or are manually deleted.

05 Digital currency and blockchain

Digital currency

Money that only exists in electronic form with no physical counterpart. It can be centralised or decentralised (not controlled by banks).

Blockchain

A digital ledger consisting of a time-stamped series of records that cannot be altered.

Transaction process:

1. The user's device encrypts payment data for security.
2. Data is sent to the blockchain network and stored in a ledger with a digital signature and time stamp.
3. Transactions are grouped into a block.
4. Each block contains a block hash (unique cryptographic code) that links it to the previous block.
5. When the block is full/confirmed, it is added to the chain across every device in the network to ensure all copies are identical.