Ch 1 · 5.1 The Internet and the World Wide Web · IGCSE Computer Science 0478
Topic 1 of 3 in The Internet and Its Uses — IGCSE Computer Science 0478 — 69 lessons.
Introduction
People often say "the internet" when they mean "the web", but they are different things. This lesson explains what actually happens in the second between typing a web address and seeing the page. (Syllabus section 5.1.)
Key ideas — The internet and the world wide web
Email, online games and video calls also use the internet but are not part of the web.
🧑🏫 Teacher's explanation
Think of the Internet as the global system of roads, highways, and tunnels that connect every city in the world. It is the physical and logical infrastructure (cables, routers, satellites) that allows data to travel from point A to point B. The World Wide Web, however, is like the collection of shops, libraries, and houses built along those roads. You use the roads to get to the shops, but the shops themselves are not the roads.
📖 Definitions
🔍 Worked example — Easy
Identify the components of the following URL: https://www.example.com/index.html
🔍 Worked example — Standard
A user enters a URL into a browser. Outline the sequence of events required to display the web page.
🔍 Worked example — Exam-style
Compare session cookies and persistent cookies in terms of their storage and usage.
⚠️ Common errors
🧠 Quick check 1
🧠 Quick check 2
🎯 Exam question
(a) Identify the protocol used in this URL. [1] (b) Explain the role of the Domain Name Server (DNS) in this process. [2] (c) State one difference between the Internet and the World Wide Web. [1] [4 marks]
Key ideas — URLs
A uniform resource locator (URL) is a text-based address for a web page. It can contain:
🧑🏫 Teacher's explanation
Think of the Internet as the global network of roads, pipes, and wires that connect every computer in the world. The World Wide Web (WWW) is not the internet; it is just one type of service that runs on top of it, like the cars and delivery trucks traveling on those roads. If the Internet is the infrastructure, the Web is the content.
📖 Definitions
🔍 Worked example — Easy
Identify the three components of the URL: http://www.example.com/images/logo.png
🔍 Worked example — Standard
A user wants to access a secure webpage. Rewrite the URL http://students.school.edu/notes.html to use the secure protocol.
🔍 Worked example — Exam-style
Analyze the URL ftp://files.server.org/data/report.pdf. Identify the protocol and the file name.
⚠️ Common errors
🧠 Quick check 1
🧠 Quick check 2
🎯 Exam question
(a) Define the term 'URL'. [1] (b) Identify the three main components that can be found within a URL. [3] [4 marks]
Key ideas — HTTP and HTTPS
HTTP (hypertext transfer protocol) is the set of rules for transferring web pages (and other files) between a web server and a browser. The browser sends a request; the server sends a response containing the page.
🧑🏫 Teacher's explanation
Imagine you are sending a letter through the mail. HTTP is like sending a postcard; anyone who handles the postcard can read exactly what you wrote. If you write your password on a postcard, a mail carrier could easily steal it. HTTPS is like putting that letter inside a heavy, locked metal box before mailing it. Even if someone intercepts the box, they cannot read the contents without the specific key.
📖 Definitions
🔍 Worked example — Easy
A user enters a URL into a browser. Identify the three main components of the URL: https://www.example.com/index.html
🔍 Worked example — Standard
Compare the security of a transaction using HTTP vs HTTPS for a banking login.
🔍 Worked example — Exam-style
A user is browsing an online store. They add a shirt to their cart and then close the browser. When they return later, the shirt is still in the cart. Identify the technology used and the type of cookie involved.
⚠️ Common errors
🧠 Quick check 1
🧠 Quick check 2
🎯 Exam question
(a) Explain why the user should ensure the website uses HTTPS rather than HTTP. [3] (b) Describe one function of a web browser that would assist the user in managing multiple shopping sites. [1] [4 marks]
Key ideas — Web browsers
The main purpose of a web browser is to render HTML (hypertext markup language) and display web pages. Functions include:
🧑🏫 Teacher's explanation
Think of the Internet as the global network of roads and highways (the infrastructure), while the World Wide Web is the collection of shops and buildings you visit using those roads. If you want to visit a specific shop, you need its address (the URL).
📖 Definitions
🔍 Worked example — Easy
Identify the three components of the following URL: https://www.example.com/products/item.html
🔍 Worked example — Standard
A user visits an online store. The browser stores their username and the items in their cart. What type of cookie is being used if the items remain in the cart even after the browser is closed and reopened?
🔍 Worked example — Exam-style
Trace the process of retrieving a web page when a user enters a URL into the address bar. List the components involved in the correct order.
⚠️ Common errors
🧠 Quick check 1
🧠 Quick check 2
🎯 Exam question
(a) Identify the protocol used in this URL. [1] (b) Describe the role of the web browser in this process. [2] (c) Explain the difference between a session cookie and a persistent cookie. [2] [5 marks]
Key ideas — How a web page is found and displayed
🧑🏫 Teacher's explanation
Think of the Internet as the global road network (the infrastructure) and the World Wide Web as the collection of shops and buildings you visit using those roads. You can't just drive to a shop by its name; you need a specific GPS coordinate to find it.
📖 Definitions
🔍 Worked example — Easy
Identify the three components of the URL: https://www.example.com/images/logo.png
🔍 Worked example — Standard
A user enters a URL. List the sequence of events from the browser to the display of the page.
🔍 Worked example — Exam-style
Compare a session cookie and a persistent cookie in terms of their storage and usage.
⚠️ Common errors
🧠 Quick check 1
🧠 Quick check 2
🎯 Exam question
(a) State the purpose of the DNS in this process. [1] (b) Describe the process that occurs between the browser sending the request and the page being displayed on the screen. [4] [5 marks]
Key ideas — Cookies
Cookies are small text files stored on the user's computer by a website, through the browser. They let the website remember information about the user.
🧑🏫 Teacher's explanation
Imagine you are visiting a massive, busy coffee shop every single day. If you walk in and the barista remembers your name, your favorite drink, and that you prefer oat milk, they have 'remembered' you. They didn't need to re-interview you; they just used a little note they kept in their pocket from your last visit.
📖 Definitions
🔍 Worked example — Easy
A user is shopping online. They add a pair of shoes to their basket. The website uses a cookie to ensure the shoes stay in the basket even if the user clicks on a different product page. What type of cookie is being used for this specific purpose during the current browsing session?
🔍 Worked example — Standard
A website stores a user's preferred language setting (e.g., 'English') using a cookie. The user closes their browser, shuts down their computer, and returns the next day. The website still displays the site in English. Identify the type of cookie used and explain why it worked.
🔍 Worked example — Exam-style
A web developer is implementing a 'Remember Me' checkbox on a login form. When checked, the user's username is saved so they don't have to re-type it next week. Categorize this cookie and list two other distinct uses for cookies mentioned in the syllabus.
⚠️ Common errors
🧠 Quick check 1
🧠 Quick check 2
🎯 Exam question
(a) Remember the items the user has placed in their shopping cart while they continue to browse the site. (b) Remember the user's preferred language for their next visit.
Worked example
Computers find each other using IP addresses, not names. The browser sends the domain name from the URL to a DNS server, which finds the matching IP address of the web server and sends it back, so the browser can request the page from the right server.
🔍 Worked example — Easy
Identify the three components of the following URL: \texttt{https://www.example.com/index.html}
🔍 Worked example — Standard
A user enters \texttt{http://science.org/lab.html} into a browser. Describe the sequence of events involving the DNS and the Web Server.
🔍 Worked example — Exam-style
Explain why a user might be able to access a website via its IP address but not via its URL.
⚠️ Common errors
Common mistakes
Practice
Answers: (1) The internet is the global infrastructure of connected networks; the web is the collection of websites and pages accessed over it. (2) Protocol https; domain name www.example.com; file name news/today.html (or today.html). (3) HTTPS encrypts the data; HTTP does not. (4) The browser sends the domain name to a DNS, which returns the IP address; the browser sends an HTTP request to the web server at that address; the server returns the HTML; the browser renders and displays the page. (5) Any two: saving personal details, tracking preferences, shopping cart, login details. Session cookies are deleted when the browser closes; persistent cookies are stored until they expire or are deleted.