5.1 The Internet and the World Wide Web

(a) Internet:

★ The word Internet comes from INTERconnected NETwork.

★ Internet is the world's largest interconnected network of computers and devices.

★ Internet Service Provider (ISP) provides Internet to the public to become part of the Internet.

★ Internet allows users to share or exchange information among users through services.

★ Allows users to chat online (via text, audio and video), send and receive emails.

(b) World Wide Web (WWW):

★ World Wide Web is a collection of websites, web-pages and other resources.

★ All web resources of WWW are accessed using the Internet.

★ It allows web-documents to be connected to other documents by hypertext links — moving from one document to another.

★ HTTP(S) protocols are written using Hypertext Mark-up Language (HTML).

★ Web-pages and other web resources are identified by Uniform Resource Locator (URL).

★ A web-browser is used to view web pages that contain text, images, video and multimedia.

(c) Difference between Internet and World Wide Web:

Other Internet services: Email (SMTP/POP/IMAP), VoIP, FTP, ATM, Telnet.

(a) ISP (Internet Service Provider):

★ Internet Service Provider (ISP) are companies that provide access to the Internet.

★ A monthly fee is usually charged for this service.

★ The ISP will set up a user account which will contain a username and a password.

(b) Services provided by ISP:

1. Internet access.
2. Domain name registration.
3. Web hosting.
4. Online storage service.
5. Email.

(a) URL — Uniform Resource Locator:

★ URL stands for "Uniform Resource Locator".

★ It is the user-friendly unique web address of the web-document or file that you wish to view.

★ URL consists of three parts:

• Protocol.
• Domain name or Website name.
• Webpage or file name.

(b) Three components of a URL:

1) Protocol:

⇒ The first part of the URL indicates which protocol the browser must use.

⇒ A protocol is a set of rules that must be obeyed when transferring data.

⇒ Usually for websites it is the HTTP protocol or its secured version HTTPS.

⇒ HTTP stands for HyperText Transfer Protocol.

⇒ HTTP defines how messages are formatted and transmitted, and what action web servers and browsers should take in response to various commands.

2) Domain name / Website name:

⇒ Domain name is the user-friendly name of a website used in place of its IP address.

⇒ Its role is to make it easier to access a given website.

3) Webpage / File name:

⇒ File name is the last part of the URL that refers to the file or web page being requested.

⇒ Web browser either downloads or reads and displays the contents of the file.

(c) Components of a Website name:

1) Domain host:

⇒ Domain host is the name of the sub-domain, a part of the main domain that can be accessed by your website visitors.

⇒ WWW indicates that the site is part of the web that provides services.

⇒ It allows websites to separate and organize content for a specific function.

2) Domain name:

⇒ Domain name is the name of the website, or the root-directory of the website.

⇒ It indicates where we want to go first on the web over the Internet.

3) Domain type:

⇒ Domain type is a domain extension name with 2 or 3 characters separated with a dot.

⇒ For example, .co, .edu, .com, .org, .net, .gov.

⇒ Domain type could include a 2-character country code extension, e.g. .uk, .in, .mv, .us.

(a) Protocol:

⇒ A protocol is an agreed-upon set of rules for exchanging data between two devices.

(b) HTTP — HyperText Transfer Protocol:

⇒ It is a request-response protocol used for transferring data between a client and a server.

⇒ It is used to load web pages using hypertext links.

⇒ It sends data in plain text format.

⇒ It does not store any information about previous requests or responses.

⇒ It sends and receives data over port 80.

(c) Difference between HTTP and HTTPS:

⇒ Both HTTP and HTTPS are request-response protocols used for transferring data between a client and a server.

⇒ HTTPS is a secure version of HTTP that ensures the safety of data when transmitted over the Internet.

⇒ HTTP sends data in plain text format making it vulnerable to interception.

⇒ HTTPS establishes an encrypted link between web-server and web-browser.

⇒ HTTP sends data over port 80 while HTTPS uses port 443.

(d) How to know whether a website is secure:

⇒ A secure website uses the https protocol in the URL.

⇒ It shows a small padlock icon in the status bar at the top-left of the address bar.

(a) Web browser:

★ Web browser is a software used to access information on the World Wide Web.

★ It is used to locate, retrieve and display the contents of the web-page or web resource.

★ It interprets, translates and displays the contents of the HTML document.

★ It interprets, translates and executes the embedded scripts (like JavaScript) inside the web page.

Examples:

(b) Three functions of a browser:

• Sends a request to the web server to provide the webpage or web resource.
• Receives data from the web server.
• Translates HTML files.
• Processes client-side script, e.g. JavaScript.
• Store / access cookies.
• Stores data in its cache.
• Identifies the protocols such as http, https, ftp etc.
• Downloading files from the web.

(c) Three features of a browser:

• Allows to Bookmark the web page which you may need later (store favourites).
• Stores History of the websites or webpages visited.
• Allows navigation forward and backward.
• Allows to reload or refresh the webpage.
• Allows multiple tabs / web pages to be opened.
• Provides Security features.
• Find specific text within a web page.
• Allows to set a homepage.

(a) Cookie:

⇒ A cookie is a text file sent by the web-server to the web-browser.

⇒ It is stored on the user's computer by the web-browser at the request of the web-server.

⇒ They are designed to hold data related to a particular client and website.

⇒ It can be accessed either by the web server or the client computer each time the user revisits the website.

(b) Three purposes of Cookies:

• It stores the website's Login information.
• It allows the detection of new and repeated visitors of the website.
• It stores the customization of the web-page (e.g. remembering where the user left off).
• It allows to track user's browsing activities and preferences (like language).
• It helps advertisers to show relevant advertisements.

(c) Are Cookies harmful?

★ No, cookies are not harmful as they are not executable program files. They are just plain text files.

(a) Session cookies:

★ Session cookies exist only in temporary memory and do not store any data on the hard drive.

★ It does not collect any information from the user's computer and does not record browsing history.

★ It stores only the user's input and tracks the movements of the user within a website.

★ For example, when making online purchases, it keeps the user's items in a virtual shopping basket.

★ Session cookies are lost when the web-browser is closed or the website session ends.

(b) Persistent (or permanent) cookies:

★ Persistent cookies are stored on the hard drive by the web-browser on the user's computer.

★ It remains on the user's hard drive until the user deletes them or they expire.

★ It stores the user's login details, settings and preferences that a user has set.

★ It removes the need to type in login details every time a certain website is visited.

★ Personal information is encrypted and stored to prevent unauthorised access.

★ It helps to create a convenient and faster website experience.

★ Persistent cookies are a very efficient way of carrying data from one session to another.

(a) How cookies store and automatically enter payment details:

⇒ A cookie is a text file sent by the web-server to the user's web-browser.

⇒ It is stored on the user's computer by the web-browser at the request of the web-server.

⇒ The user's payment details are encrypted and stored in this text file.

⇒ When the user revisits the website, the webserver requests its cookie file to access the stored payment details and automatically fills in the payment form.

(b) Why a user may be concerned about personal data and online security:

⇒ The user does not know what information is collected and stored in the cookie.

⇒ The computer could be hacked to obtain confidential data stored in cookies.

⇒ Other websites could gain unauthorised access to the cookies stored on a user's computer.

⇒ The user's profile could be built and stored in a cookie, leading to identity theft.

(a) HTML — HyperText Markup Language:

★ HTML stands for "Hyper Text Markup Language".

★ HTML is the standard markup language for creating web pages.

★ "Hypertext" refers to the text that contains hyperlinks (or links) to other documents.

★ "Markup language" refers to the way HTML tags are used to define the elements within a document.

★ It is used in processing, defining, and presenting the contents of the web page.

(b) Difference between Structure and Presentation:

Structure:

⇒ Structure is an essential part of an HTML document which includes semantic elements.

⇒ It instructs how the layout of the content is displayed.

⇒ It stores the overall contents of a web-page like Title, Headings, Paragraphs, Images, Tables.

Presentation:

⇒ Presentation is the style of the document.

⇒ It instructs how the document will give a pleasing look using different fonts, colours and sizes.

⇒ The presentation of the web-page is usually kept in a separate CSS file.

(c) (i) Three examples of HTML structure:

1. Giving the Title of the web-page, to be shown in the title bar of the web page.
2. Placement of headings and sub-headings on a web-page.
3. Placement of a paragraph of text on the web-page.
4. Placement of an image on the web-page.
5. Drawing a Table to put the contents in rows and columns on the web-page.

(ii) Three examples of HTML presentation:

1. The colour applied to a text heading, on a web-page.
2. The font style applied to a paragraph of text on a web-page.
3. The font size given to a paragraph of text on a web-page.
4. The size that an image is set to be displayed on the web-page.
5. The height and width of a table is set to be displayed on the web-page.

(d) Why HTML Structure and Presentation files are stored separately:

⇒ Separating the presentation file from the structure of the HTML allows a designer to work on either file independently.

⇒ The style of the document could be reused by its name, wherever the style is needed.

⇒ The same presentation file could be shared or used by multiple web-pages for a consistent look.

Example of HTML Structure and Presentation files:

<html>
<head>
  <title> Computer Science </title>
  <link rel="stylesheet" type="text/css"
        href="Presentation.css" />
</head>
<body>
  <h1> My First Heading </h1>
  <p class="style-1">
     My First Paragraph
  </p>
  <img src="rose.jpg" alt="flower">
</body>
</html>

h1 {
  font-family: arial;
  color: #FF0000;
  text-align: center;
  font-size: 42px;
}

.style-1 {
  font-family: times;
  color: #0000FF;
  text-align: justify;
  font-size: 24px;
}