5.1 The Internet & the World Wide Web - IGCSE Computer Science

Learning Objectives

By the end of this lesson, you will be able to:

Understand the difference between theInternetand theWorld Wide Web
Understand what is meant by aUniform Resource Locator (URL)
Describe the purpose and operation ofHTTPandHTTPS
Explain the purpose and functions of aweb browser
Describe how web pages arelocated, retrieved and displayedon a device when a user enters a URL
Explain what is meant bycookiesand how they are used, includingsession cookiesandpersistent cookies
Understand the role of: theweb browser,IP addresses,domain name server (DNS),web server,HTML

Key Terms

Internet

A global network of networks. The infrastructure used to provide connectivity to the World Wide Web.

World Wide Web (WWW)

A collection of websites and web pages that are accessed using the internet. Created in 1989 by Tim Berners-Lee.

Uniform Resource Locator (URL)

A text-based unique identifier for a web page, known as the website address. Typically contains protocol, domain name and file name.

HTTP

Hypertext Transfer Protocol — a set of rules governing communication between clients and servers for website viewing.

HTTPS

HTTP Secure — works the same as HTTP but with an added layer of security (encryption using TLS/SSL).

Web Browser

Software used to access and display information on the internet. Renders HTML to display web pages.

Web Server

A remote computer that stores the files needed to display a web page. Uses HTTP to respond to client requests.

Domain Name System (DNS)

The internet's equivalent to a phone book. Translates human-readable domain names to numeric IP addresses.

IP Address

A series of numbers that identifies any device on a network. Used for communication over the internet.

HTML

HyperText Markup Language — the foundational language used to structure and present content on the web.

CSS

Cascading Style Sheets — used to control the presentation and layout of a web page (colours, fonts, spacing).

Cookie

A tiny data file stored on a computer by browser software that holds information relating to browsing activity.

Session Cookie

A cookie that is created and replaced every time a user visits a website. Deleted when the browser is closed.

Persistent Cookie

A cookie that is saved the first time a user visits a website and retained until it expires. Also known as a permanent cookie.

Proxy Server

A system or router that acts as an intermediary between users and the internet. Used for security, filtering and caching.

Internet Service Provider (ISP)

A company that provides users with access to the internet, usually for a monthly fee.

1. The Internet vs The World Wide Web

TheInternetis the infrastructure — it is a global network of networks. TheWorld Wide Webis the collection of websites and web pages accessed using the internet. Think of the internet as the roads that connect towns and cities together, and the World Wide Web as the houses and shops you see on those roads.

The Internet

A global network of networks
The most well-known Wide Area Network (WAN)
The infrastructure used to provide connectivity to the World Wide Web
Allows users to send and receive emails, chat, and browse the web
Relies on a physical infrastructure
Makes use of TCP and IP protocols
Originated in the late 1960s as ARPANET
Think of the internet as theroadsthat connect towns and cities

The World Wide Web (WWW)

A collection of websites and web pages
Accessed using the internet
Created in 1989 by Tim Berners-Lee
Consists of interconnected documents and multimedia files stored on web servers
Web pages are accessed using a web browser
Uses HTTP / HTTPS protocols
Uses URLs to specify the location of web pages
Think of the WWW as thehouses and shopsyou see on the roads

Comparison Table: Internet vs WWW

Internet	World Wide Web
Internet is a global network of networks	WWW stands for World Wide Web
Means of connecting a computer to any other computer anywhere in the world	A collection of information accessed via the Internet
Internet is infrastructure	WWW is a service on top of that infrastructure
Can be viewed as a big book-store	Can be viewed as a collection of books on that store
Primarily hardware-based	More software-oriented
Originated in the late 1960s	Invented by Tim Berners-Lee in 1989
Superset of WWW	Subset of the Internet
First version known as ARPANET	Beginning known as NSFNET
Uses IP address	Uses HTTP / HTTPS
Users can send and receive emails	Collection of multimedia web pages and other information on websites
Makes use of TCP and IP	Uses URLs to specify the location of web pages
Worldwide collection of interconnected networks and devices	Web resources are accessed by web browsers using the internet

Real-Life Analogy

Think of theInternetas the roads that connect towns and cities together. TheWorld Wide Webcontains the things you see on the roads, like houses and shops. The roads (internet) are the infrastructure, and the buildings (websites) are what you visit.

Activity 1: Internet vs WWW

The following table shows five features of the internet and the World Wide Web. Tick the appropriate box to indicate which feature refers to the internet and which feature refers to the World Wide Web:

Feature	Internet	World Wide Web
It is possible to send and receive emails
Makes use of HTTP protocols
Uses URLs to specify the locations of websites and web pages
Resources can be accessed by using web browsers
Makes use of TCP and IP

Solution:

It is possible to send and receive emails →Internet
Makes use of HTTP protocols →World Wide Web
Uses URLs to specify the locations of websites and web pages →World Wide Web
Resources can be accessed by using web browsers →World Wide Web
Makes use of TCP and IP →Internet

Check Your Understanding: Internet vs WWW

1. What is the Internet? [2 marks]

[1]A global network of networks
[1]The infrastructure used to provide connectivity to the World Wide Web

2. What is the World Wide Web? [2 marks]

[1]A collection of websites and web pages
[1]Accessed using the internet

3. Give two differences between the Internet and the World Wide Web. [2 marks]

[1]Internet is infrastructure; WWW is a service on top of that infrastructure
[1]Internet uses IP addresses; WWW uses HTTP/HTTPS protocols

4. Who invented the World Wide Web and when? [1 mark]

[1]Tim Berners-Lee, in 1989

5. Which protocols does the Internet use and which does the WWW use? [2 marks]

[1]Internet uses TCP and IP
[1]WWW uses HTTP and HTTPS

6. What is an Internet Service Provider (ISP)? [2 marks]

[1]A company that provides users with access to the internet
[1]Usually charges a monthly fee for this service

2. Uniform Resource Locators (URLs)

AURL (Uniform Resource Locator)is a unique identifier used to locate a resource on the Internet. It is also referred to as a web address. URLs are text-based to make them easier to remember.

Structure of a URL

protocol://website address/path/file name

https://www.google.com/index.html

ProtocolDomain NameFile Name

Protocol

The communication method to transfer data between client and server.

Usually eitherhttporhttps.

Domain Name

The name of the server where the resource is located.

Domain host:www
Domain name:website name
Domain type:.com, .org, .net, .gov
Country code:.uk, .kz, .ie

File Name

The location of the file or resources on the server.

Example: /index.html or /comp_science_sample

Worked Example: Identifying Parts of a URL

URL: http://www.cie.org.uk/index.htm

Part 1:http— the protocol being used

Part 2:www.cie.org.uk— the domain name

Part 3:index.htm— the file name

Activity 2: URLs

A user typed in:https://www.hoddereducation.com/comp_science_sample

Identify:

The protocol being used
The domain host
The domain type
The file name

Solution:

Protocol:https
Domain host:www
Domain type:.com
File name:comp_science_sample

Check Your Understanding: URLs

1. What does URL stand for? [1 mark]

[1]Uniform Resource Locator

2. What are the three main parts of a URL? [3 marks]

[1]Protocol
[1]Domain name
[1]File name / web page name

3. In the URL https://www.rockict.net/index.htm, what does "https" represent? [1 mark]

[1]The protocol being used (Hypertext Transfer Protocol Secure)

4. What is the domain name in the URL https://www.savemyexams.com/igcse/computer-science? [1 mark]

[1]www.savemyexams.com

5. Why are URLs text-based? [1 mark]

[1]To make them easier to remember

6. What is the role of the file name in a URL? [1 mark]

[1]It specifies the location of the file or resources on the server

3. HTTP and HTTPS

HTTP(Hypertext Transfer Protocol) is a set of rules for transferring files — such as text, images, sound, video and other multimedia files — over the web.HTTPSis HTTP with encryption and verification.

HTTP

Stands for Hypertext Transfer Protocol
A set of rules for transferring files over the web
Allows communication between clients and servers for website viewing
Allows clients to receive data from the server (fetching a webpage) and send data to the server (submitting a form, uploading a file)
Data is sent in plain text — not secure
A website that uses HTTP has http:// in its URL

HTTPS

Stands for Hypertext Transfer Protocol Secure
Works in the same way as HTTP but with an added layer of security
All data sent and received isencrypted
Uses TLS (SSL) to encrypt normal HTTP requests and responses
Digitally signs requests and responses
Far more secure than HTTP
Used to protect sensitive information such as passwords, financial information and personal data
A website that uses HTTPS has https:// in its URL
Shows a green padlock in the status bar

HTTP	HTTPS
Hypertext Transfer Protocol	Hypertext Transfer Protocol Secure
Data is not encrypted	Data is encrypted using TLS/SSL
Less secure	More secure
Faster (no encryption overhead)	Slower (due to encryption)
Used for general browsing	Used for sensitive data (passwords, financial info)
URL begins with http://	URL begins with https://

Real-Life Example: Why HTTPS Matters

When you enter your password on a website usingHTTP, the data is sent in plain text. A hacker intercepting the data can read the password directly. When usingHTTPS, the data is encrypted, so the hacker only sees meaningless characters.

Activity 3: HTTP vs HTTPS

Describe one difference between HTTP and HTTPS. [2]
Explain why HTTPS is used for online banking. [2]

Solution:

HTTPS encrypts the data being transmitted to keep it secure, unlike HTTP [1]. HTTPS uses TLS/SSL to encrypt normal HTTP requests and responses [1].
Online banking involves sensitive information such as passwords and financial details [1]. HTTPS encrypts this data so it cannot be intercepted and read by hackers [1].

Check Your Understanding: HTTP/HTTPS

1. What does HTTP stand for? [1 mark]

[1]Hypertext Transfer Protocol

2. What is the main difference between HTTP and HTTPS? [1 mark]

[1]HTTPS encrypts the data being transmitted; HTTP does not

3. What does HTTPS use to encrypt data? [1 mark]

[1]TLS (SSL)

4. Why is HTTPS slower than HTTP? [1 mark]

[1]Due to the encryption/decryption overhead

5. What symbol might you see in the address bar when a website uses HTTPS? [1 mark]

[1]A green padlock

6. Give one example of when HTTPS should be used instead of HTTP. [1 mark]

[1]Online banking / entering passwords / any site handling sensitive data

4. Web Browsers

Aweb browseris software used to access and display information on the internet. Its main purpose is torender HTMLand display web pages.

Function	Description
Provide navigation tools	E.g. back/forward buttons and home button, to help users move between pages
Storing bookmarks & favourites	Allow users to save links to frequently visited websites and access them easily
Storing cookies	Cookies store user preferences, login details, etc.
Recording user history	Allow users to quickly revisit recently viewed web pages
Providing address bar	A place for user to type in the URL of a web page to visit
Multiple tabs	Allow multiple web pages to be open at once so users can quickly switch between them

Exam Tip

Rendering HTML is how a web browser displays web pages, but in CIE IGCSE exams, questions about functions usually expect user-facing features such as navigation tools, bookmarks, tabs, or cookies.

Activity 4: Web Browsers

Describe three features of web browsers. [3]
Describe three functions of web browsers. [3]

Solution:

Three features [3]:
- They have a home page
- Ability to store a user's favorite websites / bookmarks
- Keep a history of the websites visited / allow multiple tabs
Three functions [3]:
- Translates HTML documents and displays web pages
- Provides bookmarks and history
- Processes user inputs in the form of URLs and allows access to that page

Check Your Understanding: Web Browsers

1. What is the main purpose of a web browser? [1 mark]

[1]To render HTML and display web pages

2. Give three functions of a web browser. [3 marks]

[1]Storing bookmarks and favourites
[1]Recording user history
[1]Allowing use of multiple tabs / providing navigation tools / providing an address bar / storing cookies

3. What is a web browser? [2 marks]

[1]A piece of software used to access and display information on the internet
[1]It interprets HTML code and translates it into a visual display

4. Name two common web browsers. [2 marks]

[1]Google Chrome / Microsoft Edge / Mozilla Firefox
[1]Apple Safari / Internet Explorer

5. How does a web browser display a web page? [2 marks]

[1]It interprets/renders the HTML code from the website
[1]It displays the result as text, videos, images or sound

6. What is the role of a web browser in requesting and displaying web pages? [3 marks]

[1]Sends a request to the web server
[1]Receives web pages back from the web server
[1]Converts HTML to display the web page

5. How Web Pages are Located, Retrieved and Displayed

Web pages are held onweb servers(known as 'hosting'). To access a web page, aweb browseris used. The browser sends the domain name to aDNS, connects to the web server, and requests to access the page.HTMLis transferred and rendered by the browser, displaying the web page.

User enters URL in browser

Browser asks DNS for IP address

DNS returns IP address

Browser connects to web server

Web server sends HTML back

Browser renders HTML and displays page

Web Servers

A remote computer that stores the files needed to display a web page
Generally available 24/7
Security is managed by the owner of the hardware
Provide access to multiple users at the same time
Uses HTTP and other protocols to respond to client requests
Main job is to display website content through storing, processing and delivering webpages to users
Examples: Nginx and Apache

Domain Name System (DNS)

The Internet's equivalent to a phone book
A directory of domain names
Translates human-readable domain names to numeric IP addresses
When you type a URL, the DNS translates the domain name into its associated IP address
Without DNS, we would have to remember the IP address of every site we want to visit
DNS servers contain a database of URLs with matching IP addresses

The Six Steps of Loading a Web Page

User opens browser and types in the URL— the web browser asks DNS server 1 for the IP address of the website.
DNS server 1 cannot find the required websitein its database or cache and sends out a request to DNS server 2.
DNS server 2 finds the URLand maps it to an IP address. This IP address is sent back to DNS server 1, which puts this IP address and associated URL into its cache/database.
The IP address is then sent back to the user's computer.
The computer now sets up a communication with the website serverand the required pages are downloaded. HTML files are sent from the web server to the computer.
The user's browser interprets HTMLand displays the web pages on the user's computer.

HTML: Structure and Presentation

Structure

HTML is used to define the basic structure of a webpage by organising content into sections such as headers, paragraphs, and footers.

<!DOCTYPE html>
<html>
  <head>
    <title>My Web Page</title>
  </head>
  <body>
    <header>
      <h1>Welcome to My Website</h1>
    </header>
    <main>
      <section>
        <h2>About Me</h2>
        <p>This is a paragraph about me.</p>
      </section>
    </main>
    <footer>
      <p>Contact: myemail@example.com</p>
    </footer>
  </body>
</html>

Presentation

HTML is also used to present and display information in a visually meaningful way. This layer is mainly handled by CSS (Cascading Style Sheets).

<!DOCTYPE html>
<html>
<body>
  <h1 style="color:blue;">A Blue Heading</h1>
  <p style="color:red;">A red paragraph.</p>
</body>
</html>

CSS controls colour, font, size, spacing, positioning, background images, and different displays for different devices.

Activity 5: Loading a Web Page

A user wishes to locate a website so they can download some documents. The following sequence shows six steps in the location of the website and the download of the required documents. However, the sequence of steps shown is not in the correct order.

By writing the numbers 1 to 6, put each step in its correct order.

Order	Description of step
	The DNS server 1 cannot find the required website in its database or cache and sends out a request to DNS server 2
	The IP address is then sent back to the user's computer
	The computer now sets up a communication with the website server and the required pages are downloaded
	User opens their web browser and types in the URL; the web browser asks DNS server 1 for the IP address
	User's browser interprets HTML and displays the web pages on the user's computer
	DNS server 2 finds the URL and sends the IP address back to DNS server 1 which puts the IP address and URL into its database and cache

Solution:

Order	Description of step
1	User opens their web browser and types in the URL; the web browser asks DNS server 1 for the IP address
2	The DNS server 1 cannot find the required website in its database or cache and sends out a request to DNS server 2
3	DNS server 2 finds the URL and sends the IP address back to DNS server 1 which puts the IP address and URL into its database and cache
4	The IP address is then sent back to the user's computer
5	The computer now sets up a communication with the website server and the required pages are downloaded
6	User's browser interprets HTML and displays the web pages on the user's computer

Check Your Understanding: Loading Web Pages

1. What is a web server? [2 marks]

[1]A remote computer that stores the files needed to display a web page
[1]Uses HTTP to respond to client requests

2. What is DNS and what does it do? [2 marks]

[1]Domain Name System — a directory of domain names
[1]Translates human-readable domain names into IP addresses

3. What is an IP address? [2 marks]

[1]Internet Protocol address — a series of numbers that identifies any device on a network
[1]Used by computers to communicate with each other over the internet

4. What is HTML and what is its role? [2 marks]

[1]HyperText Markup Language — the language used to structure and present content on the web
[1]It is interpreted/rendered by the web browser to display the web page

5. Explain what is meant by HTML structure and presentation. [4 marks]

[1]Structure — the layout of the web page / how content is organised into sections
[1]Example: placing an image alongside some text / using tags such as <div>
[1]Presentation — the formatting/style of the web page / how it looks
[1]Example: the colour applied to some text / using CSS / using tags such as <font-color>

6. Explain how the information stored on a company's website is requested by the customer, sent to the customer's computer and displayed on the screen. [7 marks]

[1]A web browser is used / user enters the URL into the address bar
[1]The URL specifies the protocol — HTTP or HTTPS
[1]The domain name is used to look up the IP address of the company
[1]The DNS stores an index of domain names and IP addresses
[1]The web browser sends a request to the web server
[1]The web server sends the data for the website back to the web browser
[1]HTML is interpreted/rendered by the web browser to display the website

6. Proxy Servers

Aproxy serveris a system or router that provides a gateway between users and the internet. It acts as an intermediary between the user and a web server.

User's Computer

Proxy Server

Web Server

Functions of Proxy Servers

Allowing the internet 'traffic' to befiltered— they can block access to a website if necessary (similar type of reaction as a firewall)
By using the feature known as acache, they can speed up access to information from a website; when the website is first visited, the home page is stored on the proxy server; when the user next visits the website, it now goes through the proxy server cache instead, giving much faster access
Keeping the user'sIP address secret— this clearly improves security
Acting as afirewall

Role of a Proxy Server in a Security System

Prevents direct access to the web server / sits between user and web server
If an attack is launched it hits the proxy server instead / can be used to help prevent DDoS / help prevent hacking of web server
Traffic is examined by the proxy server / filters traffic
If traffic is invalid the request to obtain data is declined / can block requests from certain IP addresses

Activity 6: Proxy Servers

Describe the role of a proxy server in a security system. [4]
Explain how a proxy server can speed up access to a website. [2]

Solution:

Four from [4]:
- Prevents direct access to the web server / sits between user and web server
- If an attack is launched it hits the proxy server instead
- Traffic is examined/filtered by the proxy server
- If traffic is invalid the request to obtain data is declined / can block requests from certain IP addresses
Uses a cache [1]. When the website is first visited, the home page is stored on the proxy server; when the user next visits, it goes through the proxy server cache giving faster access [1].

Check Your Understanding: Proxy Servers

1. What is a proxy server? [2 marks]

[1]A system or router that provides a gateway between users and the internet
[1]Acts as an intermediary between end-users and the web pages they visit

2. Give three functions of a proxy server. [3 marks]

[1]Filtering internet traffic / blocking access to websites
[1]Caching web pages for faster access
[1]Keeping the user's IP address secret / acting as a firewall

3. How does a proxy server protect a web server from attacks? [2 marks]

[1]It sits between the user and the web server, preventing direct access
[1]If an attack is launched it hits the proxy server instead of the web server

4. What is meant by a cache in the context of a proxy server? [2 marks]

[1]A store of previously visited web pages
[1]Allows faster access when the user next visits the same website

5. How does a proxy server improve security for the user? [1 mark]

[1]It keeps the user's IP address secret

6. What happens if traffic is found to be invalid by a proxy server? [1 mark]

[1]The request to obtain data is declined

7. Cookies

Acookieis a tiny data file stored on a computer by browser software that holds information relating to your browsing activity. Typically, a cookie will contain browsing history, login information, and preferences.

What is a Cookie?

Small pieces of text sent to your browser by a website you visit
They help that website remember information about your visit
Each cookie is effectively a small look-up table containing pairs of (key, data) values, for example (surname, Jones) (music, rock)
Every time a user visits a website, it checks if it has set cookies on their browser before
If so, the browser reads the cookie which holds key information on the user's preferences such as language, currency and previous browsing activity

Session Cookies vs Persistent Cookies — Comparison Table

This is a very important exam topic. Learn the differences between the two types of cookie.

Feature	Session Cookie	Persistent Cookie
When is it created?	Created and replacedevery timea user visits a website Stored in the browser's memory	Created and saved thefirst timea user visits a website Stored in a file on the user's computer
When is it deleted?	Deleted when the session expires or is terminated Deleted when the browser window is closed Not available if the user visits again after closing the browser	Remains on the device until you erase them or they expire Lifetime is specified in the cookie itself (expiration time) Many countries have laws — these cookies are deactivated after six months
Security	Safer— no developer other than the browser can access them Doesn't actually collect any information from the user's computer Doesn't personally identify a user	Less secure Legitimate websites encrypt any personal information stored in the cookie
Typical uses	E-commerce websites — so the user can continue browsing without losing what they put in their cart Used when making online purchases	Remember a user's login details Store personal details / user preferences Hold items in an online shopping cart Track internet habits and browsing histories Target users with advertising
Key benefit	Allows continuous browsing during a single session	Removes the need to type in login details every time a website is visited

Uses of Cookies

Allow the website to remember users' passwords, email addresses and invoice details, so they won't have to insert all of this information every time they visit.
Serve as a memory, enabling the website to recognise users every time they visit it.
Save users' items in a virtual shopping basket/cart.
Track internet habits and users' website histories or favourites/bookmarks.
Target users with advertising that matches their buying or surfing habits.
Store users' preferences.
Are used in online financial transactions.
Allow progress in online games and quizzes to be stored.
Allow social networking sites to recognise preferences and browsing histories.
Allow different languages to be used on the web pages automatically as soon as users log on.

Privacy and Electronic Communications Regulations (2003)

A law that governs the use of cookies. Any website that wants to store a cookie must:

Tell users the cookies are there
Explain what the cookies are doing
Obtain users' consent to store the cookie

Activity 7: Cookies

Give two differences between session cookies and persistent cookies. [2]
Describe three uses of cookies. [3]
Explain what is meant by a session cookie. [3]
Explain what is meant by a persistent cookie. [3]
Why do you think persistent cookies are sometimes referred to as tracking cookies? Give at least two pieces of evidence to support your answer. [2]

Solution:

Session cookies are deleted when the browser is closed; persistent cookies remain until they expire [1]. Session cookies are stored in browser memory; persistent cookies are stored in a file on the user's computer [1].
Any three from: remembering login details / storing personal details / tracking user preferences / holding items in an online shopping cart / tracking internet habits / targeting advertising / storing progress in games.
Session cookies are created and replaced every time a user visits a website [1]. They are stored in the browser's memory [1]. They are deleted when the session expires or the browser window is closed [1].
Persistent cookies are saved the first time a user visits a website [1]. They remain on the device until they expire or are erased [1]. They remember a user's login details and preferences [1].
Persistent cookies can track internet habits and browsing histories [1]. They can target users with advertising that matches their buying or surfing habits [1].

Check Your Understanding: Cookies

1. What is a cookie? [2 marks]

[1]A tiny data file stored on a computer by browser software
[1]It holds information relating to your browsing activity

2. What is the difference between a session cookie and a persistent cookie? [2 marks]

[1]Session cookies are deleted when the browser is closed; persistent cookies remain on the device until they expire or are erased
[1]Session cookies are stored in browser memory; persistent cookies are stored in a file on the computer

3. Give three uses of cookies. [3 marks]

[1]Saving personal details / remembering login details
[1]Tracking user preferences
[1]Holding items in an online shopping cart

4. Why is a session cookie considered safer than a persistent cookie? [2 marks]

[1]No developer other than the browser can access session cookies
[1]Session cookies don't collect information from the user's computer or personally identify a user

5. What does the Privacy and Electronic Communications Regulations (2003) require websites to do? [3 marks]

[1]Tell users the cookies are there
[1]Explain what the cookies are doing
[1]Obtain users' consent to store the cookie

6. Explain why Victoria would use cookies as part of her website. [4 marks]

[1]To store a customer's password
[1]To store a customer's credit card details / so they do not need to be re-entered in future
[1]To track what the customer has viewed on the website
[1]So she can send them adverts that match their preferences

Key Takeaways

TheInternetis the infrastructure — a global network of networks. TheWorld Wide Webis a collection of websites and web pages accessed using the internet.
AURLis a text-based address for a web page. It contains the protocol, domain name and file name.
HTTPis a set of rules for transferring files over the web.HTTPSis HTTP with encryption (using TLS/SSL).
Aweb browserrenders HTML to display web pages. Its functions include storing bookmarks, recording history, multiple tabs, storing cookies, and providing navigation tools.
DNStranslates human-readable domain names into IP addresses.
Web serversstore the files needed to display a web page.
HTMLis used to structure and present content on the web.CSScontrols the presentation (colours, fonts, layout).
Aproxy serveracts as an intermediary between users and the internet. It filters traffic, caches web pages, and keeps the user's IP address secret.
Cookiesare tiny data files stored on a computer by browser software that hold information relating to browsing activity.
Session cookiesare created and replaced every time a user visits a website; deleted when the browser is closed.
Persistent cookiesare saved the first time a user visits a website; retained until they expire.
ThePrivacy and Electronic Communications Regulations (2003)require websites to inform users about cookies and obtain consent.

Question Bank

1. Explain the fundamental differences between the Internet and the World Wide Web. [4 marks]

[1]The Internet is a global network of networks / infrastructure
[1]The WWW is a collection of websites and web pages accessed via the internet
[1]The Internet uses IP addresses / TCP/IP
[1]The WWW uses HTTP/HTTPS protocols

2. A user typed in: https://www.hoddereducation.com/comp_science_sample. Identify: (i) the protocol being used (ii) the domain host (iii) the domain type (iv) the file name. [4 marks]

[1](i) Protocol: https
[1](ii) Domain host: www
[1](iii) Domain type: .com
[1](iv) File name: comp_science_sample

3. Describe three features of web browsers. [3 marks]

[1]They have a home page / ability to store bookmarks and favourites
[1]They keep a history of websites visited / allow navigation backward and forward
[1]Multiple tabs can be open at the same time / provide an address bar

4. Describe three functions of web browsers. [3 marks]

[1]Translates HTML documents and displays web pages
[1]Provides bookmarks and history
[1]Identifies protocols / processes user inputs in the form of URLs

5. A user wishes to locate a website so they can download some documents. By writing the numbers 1 to 6, put each step in its correct order. [6 marks]

1— User opens their web browser and types in the URL; the web browser asks DNS server 1 for the IP address
2— The DNS server 1 cannot find the required website in its database and sends out a request to DNS server 2
3— DNS server 2 finds the URL and sends the IP address back to DNS server 1 which puts the IP address and URL into its database and cache
4— The IP address is then sent back to the user's computer
5— The computer now sets up a communication with the website server and the required pages are downloaded
6— The user's browser interprets HTML and displays the web pages on the user's computer

6. Explain what is meant by a session cookie. [3 marks]

[1]A cookie created and replaced every time a user visits a website
[1]Stored in the browser's memory
[1]Deleted when the session expires or the browser window is closed

7. Explain what is meant by a persistent cookie. [3 marks]

[1]A cookie saved the first time a user visits a website
[1]Retained until it expires or is erased
[1]Remembers a user's login details and preferences

8. Give three uses of cookies. [3 marks]

[1]Saving personal details / remembering login details
[1]Tracking user preferences
[1]Holding items in an online shopping cart

9. Describe the role of an Internet Service Provider (ISP). [6 marks]

[1]Provide access to the internet / dial-up / broadband
[1]Usually charge a monthly fee
[1]Monitor usage / give users an IP address
[1]Determine bandwidth / support domain names
[1]Provide security services / web hosting facilities
[1]Provide access to email / online data storage

10. Describe the role of a proxy server in a security system. [4 marks]

[1]Prevents direct access to the web server / sits between user and web server
[1]If an attack is launched it hits the proxy server instead
[1]Traffic is examined/filtered by the proxy server
[1]If traffic is invalid the request to obtain data is declined / can block requests from certain IP addresses

11. Explain how the information stored on a company's website is requested by the customer, sent to the customer's computer and displayed on the screen. [7 marks]

[1]A web browser is used / user enters the URL into the address bar
[1]The URL specifies the protocol — HTTP or HTTPS
[1]The domain name is used to look up the IP address of the company
[1]The DNS stores an index of domain names and IP addresses
[1]The web browser sends a request to the web server
[1]The web server sends the data for the website back to the web browser
[1]HTML is interpreted/rendered by the web browser to display the website

12. Describe what is meant by HTTPS. [2 marks]

[1]Hypertext Transfer Protocol Secure
[1]It means the data sent to and from the web server is encrypted / uses SSL/TLS

13. Explain what is meant by cookies. [2 marks]

[1]Small packets of data / text files
[1]Stored by the web browser on the user's computer

14. The table shows four definitions. Complete the table giving the missing Term for each definition. [4 marks]

[1]A data transmission method that sends data one bit at a time, down a single wire →Serial
[1]An address given to a device on a network. The address is assigned by the network →IP (address)
[1]The software used to render HTML and display a web page →Browser
[1]An address given to a device at the manufacturing stage that can be used to identify the device on a network →MAC (address)

15. Complete the sentences using the terms: browser, Internet Service Provider (ISP), protocol, IP address, webpages, Internet. [6 marks]

[1]Abrowseris a program that allows a user to viewwebpages.
[1]AnInternet Service Provider (ISP)is a company that provides a connection to access theInternet.
[1]The mainprotocolthat governs the transmission of data using the Internet is http.
[1]TheIP addressis provided by the network, and given to each device on the network.
[1]The browser sends a request to the web server.
[1]The web server sends the data for the website back to the browser, which interprets the HTML to display the webpage.