Chapter 8: Web Development with HTML, CSS, and JavaScript – Solved Exercise

Solved Multiple Choice Questions with Explanations & Tips

1. Which of the following tag is not a correct HTML tag?

  • (a) <div>
  • (b) <span>
  • (c) <head>
  • (d) <footer>
    Answer: None of these (All are correct HTML tags)

🔹 Explanation:
All four options (<div>, <span>, <head>, <footer>) are valid HTML tags. <div> and <span> are used for structuring and styling, <head> contains metadata, and <footer> represents the footer section of a webpage.

💡 Tip: Always check the latest HTML specifications for valid tags. You can refer to MDN Web Docs for updated information.


2. What does CSS stand for?

  • (a) Cascading Style Sheets
  • (b) Computer Style Sheets
  • (c) Creative Style Sheets
  • (d) Colorful Style Sheets
    Answer: (a) Cascading Style Sheets

🔹 Explanation:
CSS stands for Cascading Style Sheets, which is used to define the presentation of HTML documents, including layout, colors, and fonts.

💡 Tip: The word “Cascading” refers to how styles are applied in a hierarchy, from external stylesheets to inline styles.


3. Which of the following tag is used to create a hyperlink in HTML?

  • (a) <link>
  • (b) <a>
  • (c) <href>
  • (d) <nav>
    Answer: (b) <a>

🔹 Explanation:
The <a> (anchor) tag is used to create hyperlinks in HTML. The href attribute inside the <a> tag specifies the link’s destination.

💡 Tip: Use the target="_blank" attribute to open links in a new tab, like this: <a href="https://example.com" target="_blank">Click Here</a>.


4. Which property is used to change the background color in CSS?

  • (a) color
  • (b) background-color
  • (c) bgcolor
  • (d) background
    Answer: (b) background-color

🔹 Explanation:
The background-color property is used to set the background color of an element in CSS.

💡 Tip: Use color for text color and background-color for background color. Example:

body {
  background-color: lightblue;
}

5. Which HTML attribute is used to define inline styles?

  • (a) class
  • (b) style
  • (c) font
  • (d) styles
    Answer: (b) style

🔹 Explanation:
The style attribute allows inline CSS styling directly in an HTML tag.

💡 Tip: Avoid excessive use of inline styles; instead, use external CSS for better maintainability.
Example:

<p style="color: red;">This is a red text.</p>

6. Which of the following is the correct syntax for a CSS rule?

  • (a) selector {property: value;}
  • (b) selector: {property=value;}
  • (c) selector {property=value}
  • (d) selector: {property: value;}
    Answer: (a) selector {property: value;}

🔹 Explanation:
CSS rules follow the syntax:

selector {
  property: value;
}

💡 Tip: Always end CSS statements with a semicolon (;) to avoid errors.


7. In JavaScript, which markup is used for comments?

  • (a) /* */
  • (b) //
  • (c) <–
  • (d) /* */
    Answer: Both (a) and (b)

🔹 Explanation:

  • Single-line comments: // This is a comment
  • Multi-line comments: /* This is a multi-line comment */

💡 Tip: Use comments to explain code but avoid excessive commenting in obvious cases.


8. How do you include JavaScript in an HTML document?

  • (a) <script src="script.js"></script>
  • (b) <java src="script.js"></java>
  • (c) <js src="script.js"></js>
  • (d) <code src="script.js"></code>
    Answer: (a) <script src="script.js"></script>

🔹 Explanation:
JavaScript is included in HTML using the <script> tag, either inline or by linking an external file.

💡 Tip: Place <script> before the closing </body> tag to improve page load speed.


9. Which HTML tag is used to create an unordered list?

  • (a) <ol>
  • (b) <ul>
  • (c) <li>
  • (d) <list>
    Answer: (b) <ul>

🔹 Explanation:
The <ul> tag is used for unordered (bulleted) lists, whereas <ol> is for ordered (numbered) lists.

💡 Tip: Use <li> inside <ul> or <ol> to define list items.
Example:

<ul>
  <li>Item 1</li>
  <li>Item 2</li>
</ul>

10. Which tag is used to display a horizontal line in HTML?

  • (a) <br>
  • (b) <hr>
  • (c) <line>
  • (d) <hline>
    Answer: (b) <hr>

🔹 Explanation:
The <hr> (horizontal rule) tag creates a horizontal line in HTML, typically used to separate content.

💡 Tip: Customize the appearance using CSS, e.g.:

hr {
  border: 2px solid black;
}

Solved Short Questions (Simple & Easy Language)

1. What is the purpose of the <head> tag in HTML?

The <head> tag contains important information about the web page that is not visible to users. It includes:

  • The title of the page (<title>)
  • Links to CSS files (<link>)
  • Meta information (<meta>)
  • JavaScript files (<script>)

2. Explain the difference between an ordered list and an unordered list in HTML.

  • Ordered List (<ol>): It shows items in a numbered format (1, 2, 3…).
  • Unordered List (<ul>): It shows items with bullet points (●, ■, ○).

Example:

<ol>
  <li>First Item</li>
  <li>Second Item</li>
</ol>

<ul>
  <li>First Item</li>
  <li>Second Item</li>
</ul>

3. How do you add a comment in CSS?

In CSS, we use /* */ for comments.
Example:

/* This is a comment */
p {
  color: blue; /* This line changes text color to blue */
}

Comments are ignored by the browser and are used to explain code.


4. What are the different ways to apply CSS to an HTML document?

There are three ways to apply CSS:

  1. Inline CSS – Written inside the HTML tag using the style attribute. <p style="color: red;">Hello</p>
  2. Internal CSS – Written inside the <style> tag in the <head> section. <style> p { color: blue; } </style>
  3. External CSS – Written in a separate .css file and linked using <link>. <link rel="stylesheet" href="style.css">

5. How can you include JavaScript in an HTML file?

We can include JavaScript in two ways:

  1. Inline JavaScript: Inside the <script> tag in the HTML file. <script> alert("Hello World!"); </script>
  2. External JavaScript: Linking a separate JavaScript file (.js). <script src="script.js"></script>

6. Describe the syntax for creating a hyperlink in HTML.

A hyperlink is created using the <a> tag with the href attribute.
Example:

<a href="https://www.google.com">Visit Google</a>

This will create a clickable link that opens Google.


7. What is the function of the <div> tag in HTML?

The <div> tag is used to group other HTML elements together. It helps in styling and layout design.

Example:

<div style="background-color: lightgray; padding: 10px;">
  <p>This is inside a div.</p>
</div>

It is like a container for other elements.


8. How do you link an external CSS file to an HTML document?

We use the <link> tag inside the <head> section.

Example:

<link rel="stylesheet" href="style.css">

This connects an external style.css file to the HTML page.


9. What is the use of the <table> tag in HTML?

The <table> tag is used to create tables to display data in rows and columns.

Example:

<table border="1">
  <tr>
    <th>Name</th>
    <th>Age</th>
  </tr>
  <tr>
    <td>Ali</td>
    <td>15</td>
  </tr>
</table>

This will create a simple table with a border.


10. Explain the box model in CSS.

The CSS box model explains how elements are displayed on a webpage. It includes:

  1. Content – The main text or image inside the box.
  2. Padding – Space inside the box, around the content.
  3. Border – The outer edge of the box.
  4. Margin – Space outside the box, separating it from other elements.

Example:

div {
  width: 200px;
  padding: 10px;
  border: 5px solid black;
  margin: 20px;
}

This defines a box with content, padding, border, and margin.


💡 Tip for Students: Keep practicing with small HTML and CSS examples to understand better. 🚀

Solved Long Questions (Simple & Easy for Class 9)


1. Discuss the fundamental differences between HTML, CSS, and JavaScript in the context of web development.

In web development, HTML, CSS, and JavaScript work together to create a complete website. Here’s how they differ:

FeatureHTMLCSSJavaScript
PurposeStructure of a webpageStyling and designMakes the webpage interactive
What it doesDefines headings, paragraphs, images, tables, etc.Changes colors, fonts, layout, and animationsAdds buttons, forms, and real-time interactions
Example<h1>Heading</h1>h1 { color: red; }document.write("Hello!");

🔹 Simple Example:

<!DOCTYPE html>
<html>
<head>
    <style>
        h1 { color: blue; }
    </style>
    <script>
        function showMessage() {
            alert("Hello, this is JavaScript!");
        }
    </script>
</head>
<body>
    <h1>Welcome to Web Development</h1>
    <button onclick="showMessage()">Click Me</button>
</body>
</html>

HTML creates the heading and button.
CSS makes the heading blue.
JavaScript makes the button show an alert when clicked.


2. Explain the process of setting up a development environment for web development.

To start web development, you need some basic software and tools:

1. Text Editor (for writing code)

  • Notepad++ (Simple and easy)
  • VS Code (Popular among developers)

2. Web Browser (for testing webpages)

  • Google Chrome (Best for development)
  • Mozilla Firefox

3. Local Web Server (for testing advanced web pages)

  • XAMPP (For PHP and databases)

4. Steps to Set Up

  1. Install VS Code and a web browser.
  2. Open VS Code and create an index.html file.
  3. Write a basic HTML page and save it.
  4. Open the file in a web browser to see your webpage.

💡 Tip: Always save your file with .html extension before testing.


3. Create a basic HTML page that includes a header, a paragraph, an image, and a hyperlink.

Code for a simple webpage:

<!DOCTYPE html>
<html>
<head>
    <title>My First Webpage</title>
</head>
<body>
    <h1>Welcome to My Website</h1>
    <p>This is my first webpage. I am learning HTML!</p>
    <img src="image.jpg" alt="A beautiful scenery" width="300">
    <br>
    <a href="https://www.google.com">Click here to visit Google</a>
</body>
</html>

💡 Save this as index.html and open it in a browser.


4. How do you style a table using CSS? Create a sample table and apply styles to it.

HTML Table with CSS Styling

<!DOCTYPE html>
<html>
<head>
    <style>
        table {
            width: 50%;
            border-collapse: collapse;
        }
        th, td {
            border: 1px solid black;
            padding: 10px;
            text-align: center;
        }
        th {
            background-color: lightblue;
        }
        tr:nth-child(even) {
            background-color: lightgray;
        }
    </style>
</head>
<body>
    <h2>Student Marks</h2>
    <table>
        <tr>
            <th>Name</th>
            <th>Marks</th>
        </tr>
        <tr>
            <td>Ali</td>
            <td>85</td>
        </tr>
        <tr>
            <td>Sara</td>
            <td>90</td>
        </tr>
    </table>
</body>
</html>

💡 Tip: Use border-collapse: collapse; to remove space between table borders.


5. Describe the different CSS selectors and provide examples of each.

Selector TypeExampleDescription
Element Selectorp { color: red; }Styles all <p> tags.
Class Selector.highlight { color: blue; }Styles elements with class="highlight".
ID Selector#title { font-size: 20px; }Styles an element with id="title".
Group Selectorh1, h2 { text-align: center; }Styles multiple elements together.

Example:

#main {
    color: green;
}
.highlight {
    background-color: yellow;
}

💡 Tip: Use classes when styling multiple elements and IDs for unique elements.


6. Explain the process of creating a responsive web page using CSS.

A responsive webpage adjusts its layout for different screen sizes.

Example using Media Queries:

body {
    font-size: 16px;
}
@media (max-width: 600px) {
    body {
        font-size: 12px;
    }
}

🔹 Explanation:

  • The font size is 16px by default.
  • When the screen width is 600px or smaller, the font size reduces to 12px.

💡 Tip: Use flexbox and grid for better responsive design.


7. Write a JavaScript function that changes the background color of a web page when a button is clicked.

HTML + JavaScript Code:

<!DOCTYPE html>
<html>
<head>
    <script>
        function changeColor() {
            document.body.style.backgroundColor = "lightblue";
        }
    </script>
</head>
<body>
    <button onclick="changeColor()">Click to Change Color</button>
</body>
</html>

🔹 Explanation:

  • The onclick event runs the changeColor() function when the button is clicked.
  • document.body.style.backgroundColor = "lightblue"; changes the background color.

💡 Tip: You can use "random" colors using Math.random().


8. How do you add animations and transitions using CSS?

Example of a simple animation:

@keyframes move {
    from { left: 0px; }
    to { left: 200px; }
}

.box {
    position: relative;
    width: 100px;
    height: 100px;
    background-color: red;
    animation: move 2s linear infinite;
}

Example of a button with transition:

button {
    background-color: blue;
    color: white;
    padding: 10px;
    transition: background-color 0.5s;
}
button:hover {
    background-color: green;
}

🔹 Explanation:

  • Animation moves a box from left to right.
  • Transition smoothly changes button color when hovered.

💡 Tip: Use ease-in-out for smoother effects.


🔥 Conclusion: Learning HTML, CSS, and JavaScript step by step helps in building amazing websites. Keep practicing and experimenting with code! 🚀

Computational Thinking – Chapter 7 Class 9th (New Syllabus) | All Punjab Boards

Learn Computational Thinking from Chapter 7 of 9th class computer science (new syllabus) for all Punjab boards. Understand problem-solving, algorithms, decomposition, and logical reasoning with easy explanations.

Slug:

Multiple Choice Questions with Answers, Explanations, and Tips

1. Which of the following best defines computational thinking?

Options:
(a) A method of solving problems using mathematical calculations only.
(b) A problem-solving approach that employs systematic, algorithmic, and logical thinking. ✅
(c) A technique used exclusively in computer programming.
(d) An approach that ignores real-world applications.

Answer: (b) A problem-solving approach that employs systematic, algorithmic, and logical thinking.

Explanation: Computational thinking is a structured way of thinking that helps in solving problems efficiently by using logical steps, pattern recognition, decomposition, and abstraction. It is not limited to mathematics or programming.

Tip: Think of computational thinking as a way to approach complex problems in a systematic manner, not just in coding but in real life too.


2. Why is problem decomposition important in computational thinking?

Options:
(a) It simplifies problems by breaking them down into smaller, more manageable parts. ✅
(b) It complicates problems by adding more details.
(c) It eliminates the need for solving the problem.
(d) It is only useful for simple problems.

Answer: (a) It simplifies problems by breaking them down into smaller, more manageable parts.

Explanation: Problem decomposition helps in handling complex problems by dividing them into smaller sections, making them easier to solve.

Tip: Think of decomposition like assembling a puzzle—solving smaller pieces first makes the entire picture clearer.


3. Pattern recognition involves:

Options:
(a) Finding and using similarities within problems ✅
(b) Ignoring repetitive elements
(c) Breaking problems into smaller pieces
(d) Writing detailed algorithms

Answer: (a) Finding and using similarities within problems

Explanation: Pattern recognition is the ability to identify common trends or repeated structures in problems, making them easier to solve.

Tip: Look for repeating patterns in different problems to speed up finding solutions.


4. Which term refers to the process of ignoring the details to focus on the main idea?

Options:
(a) Decomposition
(b) Pattern recognition
(c) Abstraction ✅
(d) Algorithm design

Answer: (c) Abstraction

Explanation: Abstraction is the process of removing unnecessary details to focus on the essential aspects of a problem.

Tip: When dealing with a problem, try to remove unnecessary information and focus only on what matters.


5. Which of the following is a principle of computational thinking?

Options:
(a) Ignoring problem understanding
(b) Problem simplification ✅
(c) Avoiding solution design
(d) Implementing random solutions

Answer: (b) Problem simplification

Explanation: Simplifying a problem helps make it more manageable and easier to solve, which is a key aspect of computational thinking.

Tip: Always break problems into smaller, simpler parts before attempting a solution.


6. Algorithms are:

Options:
(a) Lists of data
(b) Graphical representations
(c) Step-by-step instructions for solving a problem ✅
(d) Repetitive patterns

Answer: (c) Step-by-step instructions for solving a problem

Explanation: An algorithm is a set of defined steps that provide a systematic way to solve a problem.

Tip: Algorithms should always be clear, efficient, and executable.


7. Which of the following is the first step in problem-solving according to computational thinking?

Options:
(a) Writing the solution
(b) Understanding the problem ✅
(c) Designing a flowchart
(d) Selecting a solution

Answer: (b) Understanding the problem

Explanation: Before solving a problem, it is essential to fully understand its nature, requirements, and constraints.

Tip: Read and analyze the problem carefully before jumping into solutions.


8. Flowcharts are used to:

Options:
(a) Code a program
(b) Represent algorithms graphically ✅
(c) Solve mathematical equations
(d) Identify patterns

Answer: (b) Represent algorithms graphically

Explanation: Flowcharts provide a visual representation of an algorithm, making it easier to understand and follow.

Tip: Use flowcharts to map out problem solutions before writing actual code.


9. Pseudocode is:

Options:
(a) A type of flowchart
(b) A high-level description of an algorithm using plain language ✅
(c) A programming language
(d) A debugging tool

Answer: (b) A high-level description of an algorithm using plain language

Explanation: Pseudocode is a way to describe an algorithm in simple, structured language before converting it into a programming language.

Tip: Write pseudocode before coding to ensure a logical flow in your program.

Short Questions with Simple Answers

  1. Define computational thinking.
    Answer: Computational thinking is a problem-solving approach that involves breaking down problems, recognizing patterns, using abstraction, and designing algorithms to solve them systematically.
  2. What is decomposition in computational thinking?
    Answer: Decomposition is the process of breaking a complex problem into smaller, more manageable parts to make it easier to solve.
  3. Explain pattern recognition with an example.
    Answer: Pattern recognition involves identifying similarities or repeating patterns in problems. Example: In math, recognizing that multiplication is repeated addition helps solve large problems faster.
  4. Describe abstraction and its importance in problem-solving.
    Answer: Abstraction means focusing on the main idea while ignoring unnecessary details. It helps simplify complex problems and makes solutions more general and reusable.
  5. What is an algorithm?
    Answer: An algorithm is a step-by-step set of instructions for solving a problem or completing a task.
  6. How does problem understanding help in computational thinking?
    Answer: Understanding the problem fully ensures that the correct approach is used to find an efficient solution.
  7. What are flowcharts and how are they used?
    Answer: Flowcharts are diagrams that visually represent the steps of an algorithm. They help in planning and understanding processes easily.
  8. Explain the purpose of pseudocode.
    Answer: Pseudocode is a simple way of writing an algorithm using plain language before converting it into actual code. It helps in planning and understanding logic.
  9. How do you differentiate between flowcharts and pseudocode?
    Answer: Flowcharts use diagrams to show the steps of an algorithm, while pseudocode uses simple text-based instructions.
  10. What is a dry run and why is it important?
    Answer: A dry run is manually going through an algorithm step by step with sample inputs to check for errors before running it on a computer. It helps in debugging.
  11. Describe LARP and its significance in learning algorithms.
    Answer: LARP (Live Action Role Play) is a method where people act out algorithmic steps to understand concepts better. It makes learning interactive and fun.
  12. List and explain two debugging techniques.
    Answer:
  • Print Statements: Adding print statements in code to check values at different stages.
  • Step-by-Step Execution: Running the program one step at a time to identify errors.

Long Questions with Simple Answers


1. Algorithm for Assigning a Grade Based on Marks

Algorithm:

  1. Start
  2. Input the student’s marks
  3. If marks are 90 or above, assign A+
  4. Else if marks are 80 to 89, assign A
  5. Else if marks are 70 to 79, assign B
  6. Else if marks are 60 to 69, assign C
  7. Else assign F
  8. Display the grade
  9. End

2. Using Flowcharts and Pseudocode for Solving Complex Problems

Flowcharts and pseudocode help in organizing the steps of solving a problem.

Example: Online Payment Process

  • Flowchart: Shows steps like “Enter card details,” “Verify payment,” and “Approve or Reject.”
  • Pseudocode: Uses text to describe the process step by step before coding it.

Why Use Them?

  • Flowcharts give a visual representation.
  • Pseudocode helps in writing logic clearly before coding.

3. Computational Thinking and Its Significance

Definition: Computational thinking is a way of solving problems using logical steps, breaking down problems, finding patterns, and designing solutions.

Examples:

  • In Healthcare: AI uses computational thinking to predict diseases.
  • In Business: Companies analyze customer data for better marketing.

Why Important?

  • Helps solve complex problems
  • Improves efficiency
  • Used in different fields like education, science, and finance

4. Decomposition in Computational Thinking

Definition: Breaking a big problem into smaller, easier parts.

Example:

To create a calculator app, break it into:

  1. User interface
  2. Buttons for numbers
  3. Mathematical operations
  4. Displaying results

Why Important?

  • Makes complex tasks manageable
  • Helps in debugging and reusing code

5. Pattern Recognition in Problem-Solving

Definition: Finding similarities and trends in problems.

Example:

  • In math, noticing that multiplication is repeated addition.
  • In coding, recognizing a loop is needed for repeating tasks.

Why Important?

  • Speeds up problem-solving
  • Helps create efficient algorithms

6. Abstraction in Computational Thinking

Definition: Focusing on important details while ignoring unnecessary ones.

Example:

  • Google Maps hides extra details and only shows routes.
  • Video games don’t show how physics calculations work, just the final action.

Why Important?

  • Simplifies problems
  • Reduces complexity

7. What is an Algorithm?

Definition: A step-by-step set of instructions to solve a problem.

Example: Algorithm for Making Tea

  1. Boil water
  2. Add tea leaves
  3. Wait for 2 minutes
  4. Add milk and sugar
  5. Serve

Role in Computational Thinking:

  • Provides a clear solution
  • Helps in automation

8. Flowcharts vs. Pseudocode

FeatureFlowchartsPseudocode
FormatVisual diagramText-based
Ease of UseEasy to understandCloser to real coding
When to Use?For planning visuallyBefore writing real code

Example:

  • Flowcharts are better for explaining to non-coders.
  • Pseudocode is better when writing real code later.

9. What is a Dry Run?

Definition: Testing an algorithm manually before running it on a computer.

Example:

If an algorithm adds two numbers, test it with 5 + 3 = 8 before coding.

Why Important?

  • Helps find mistakes early
  • Ensures correct logic

10. What is LARP?

Definition: Live Action Role Play (LARP) is acting out an algorithm in real life to understand it better.

Example:

Students act as different parts of a computer (CPU, RAM, etc.) to learn how they work.

Why Important?

  • Makes learning fun and interactive
  • Improves understanding of algorithms

11. How LARP Helps in Computational Thinking?

Definition: LARP makes abstract concepts real by physically acting them out.

Example:

  • In a sorting algorithm, students can hold number cards and arrange themselves in order.

Why Important?

  • Helps students visualize algorithms
  • Encourages active learning

Introduction to Computer Networks – 9th Class Computer Science (New Syllabus)

Discover the basics of computer networks in 9th class computer science (new syllabus). Understand networking types, protocols, security, and real-world applications with simple explanations.

MCQs


1. What is the primary objective of computer networks?

Options:
(a) Increase computational power
(b) Enable resource sharing and data communication ✅
(c) Enhance graphic capabilities
(d) Improve software development

Explanation:
The primary goal of computer networks is to allow multiple devices to communicate and share resources such as files, printers, and the internet.

Tip:
Always focus on the main purpose—data sharing and communication in networks.


2. Which device is used to connect multiple networks and direct data packets between them?

Options:
(a) Switch
(b) Hub
(c) Router ✅
(d) Modem

Explanation:
A router connects different networks and determines the best path for forwarding data packets between them.

Tip:

  • A switch is used within a network to connect devices.
  • A hub is a basic networking device that broadcasts data to all connected devices.
  • A modem connects a network to the internet.

3. Which layer of the OSI model is responsible for node-to-node data transfer and error detection?

Options:
(a) Physical Layer
(b) Data Link Layer ✅
(c) Network Layer
(d) Transport Layer

Explanation:
The Data Link Layer ensures error detection and node-to-node data transfer, using protocols like Ethernet and MAC addressing.

Tip:

  • Physical Layer deals with hardware transmission (cables, signals).
  • Network Layer handles IP addressing and routing.
  • Transport Layer ensures end-to-end delivery (e.g., TCP/UDP).

4. What is the function of the Domain Name System (DNS)?

Options:
(a) Assign IP addresses dynamically
(b) Translate domain names to IP addresses ✅
(c) Secure data communication
(d) Monitor network traffic

Explanation:
DNS translates human-readable domain names (e.g., google.com) into IP addresses (e.g., 8.8.8.8), allowing browsers to access websites.

Tip:

  • DHCP assigns IP addresses dynamically.
  • DNS only translates domain names.

5. Which method of data transmission uses a dedicated communication path?

Options:
(a) Packet Switching
(b) Circuit Switching ✅
(c) Full-Duplex
(d) Half-Duplex

Explanation:
Circuit Switching establishes a dedicated communication path between sender and receiver (e.g., traditional telephone calls).

Tip:

  • Packet Switching (used in the internet) divides data into packets sent over different routes.
  • Full-Duplex & Half-Duplex relate to communication direction.

6. What is encapsulation in the context of network communication?

Options:
(a) Converting data into a secure format
(b) Wrapping data with protocol information ✅
(c) Monitoring network traffic
(d) Translating domain names to IP addresses

Explanation:
Encapsulation is the process of adding protocol-specific headers and trailers to data as it moves through network layers.

Tip:
Encapsulation follows the OSI model:

  1. Application Layer (data)
  2. Transport Layer (segments)
  3. Network Layer (packets)
  4. Data Link Layer (frames)
  5. Physical Layer (bits)

7. Which protocol is used for reliable data transfer in the TCP/IP model?

Options:
(a) HTTP
(b) FTP
(c) TCP ✅
(d) UDP

Explanation:
TCP (Transmission Control Protocol) ensures reliable data transmission using error checking and acknowledgment.

Tip:

  • UDP (User Datagram Protocol) is faster but unreliable (used in streaming).
  • HTTP & FTP are application-layer protocols.

8. What is the main purpose of a firewall in network security?

Options:
(a) Convert data into a secure format
(b) Monitor and control network traffic ✅
(c) Assign IP addresses
(d) Translate domain names

Explanation:
A firewall acts as a security barrier, filtering incoming and outgoing traffic based on predefined rules.

Tip:
Firewalls prevent unauthorized access and cyber attacks.


9. Which network topology connects all devices to a central hub?

Options:
(a) Ring
(b) Mesh
(c) Bus
(d) Star ✅

Explanation:
In a Star Topology, all devices are connected to a central hub or switch, which manages communication.

Tip:

  • Ring Topology: Devices are connected in a loop.
  • Mesh Topology: Every device is interconnected.
  • Bus Topology: A single central cable connects all devices.

10. What is a key benefit of using computer networks in businesses?

Options:
(a) Increase computational power
(b) Enable resource sharing and efficient communication ✅
(c) Enhance graphic capabilities
(d) Improve software development

Explanation:
Computer networks enhance communication and allow resource sharing, reducing costs and improving efficiency.

Tip:

  • Always focus on connectivity and resource-sharing when answering network-related benefits.

Short Questions with Answers

1. Define data communication and list its key components.
Answer: Data communication is the exchange of data between devices through a transmission medium. The key components are:

  • Sender (originates data)
  • Receiver (accepts data)
  • Transmission Medium (carries data)
  • Message (actual data being transmitted)
  • Protocol (rules governing communication)

Key Words: Data exchange, sender, receiver, transmission, protocol


2. Explain the role of routers in a computer network.
Answer: Routers direct data packets between networks, ensuring efficient data transmission by selecting the best path. They connect different networks, manage traffic, and provide security features like firewalls.

Key Words: Data packets, network connection, routing, path selection, traffic management


3. What are the main functions of the Network Layer in the OSI model?
Answer: The Network Layer is responsible for:

  • Logical addressing (assigning IP addresses)
  • Routing (determining the best path)
  • Packet forwarding (moving data across networks)
  • Fragmentation (breaking data into smaller packets)

Key Words: IP addressing, routing, forwarding, fragmentation


4. Describe the difference between packet switching and circuit switching.
Answer:

  • Packet Switching: Data is broken into packets, which travel independently and reassemble at the destination (e.g., Internet).
  • Circuit Switching: A dedicated communication path is established for the entire session (e.g., telephone calls).

Key Words: Packet-based, independent transmission, dedicated path, real-time communication


5. What is the purpose of the Dynamic Host Configuration Protocol (DHCP)?
Answer: DHCP automatically assigns IP addresses to devices in a network, reducing manual configuration and ensuring efficient IP management.

Key Words: IP assignment, automation, network configuration, address management


6. How does encapsulation ensure secure communication in a network?
Answer: Encapsulation wraps data with headers and encryption, protecting it during transmission. It helps maintain integrity, confidentiality, and proper data routing.

Key Words: Data protection, headers, encryption, security, integrity


7. Differentiate between TCP and UDP in terms of data transfer reliability.
Answer:

  • TCP (Transmission Control Protocol): Reliable, connection-oriented, ensures data delivery with error checking.
  • UDP (User Datagram Protocol): Faster, connectionless, no guarantee of delivery but efficient for real-time applications.

Key Words: Reliable, connection-oriented, error checking, fast, connectionless


8. Explain the importance of encryption in network security.
Answer: Encryption converts data into an unreadable format, preventing unauthorized access and ensuring confidentiality, integrity, and secure communication.

Key Words: Data security, confidentiality, encryption, unauthorized access


9. What are the advantages of using a star topology in a network?
Answer:

  • Easy Troubleshooting: Faults are isolated to a single device.
  • Scalability: Easy to add new devices.
  • Better Performance: Dedicated links prevent data collisions.

Key Words: Central hub, easy maintenance, scalability, reliability


10. How do firewalls contribute to network security?
Answer: Firewalls monitor and filter incoming/outgoing traffic, blocking unauthorized access and preventing cyber threats like malware and hacking attempts.

Key Words: Traffic filtering, security, unauthorized access, malware prevention

Here are the detailed answers for your long questions, suitable for a 9th-grade level:


1. Objectives of Computer Networks and Resource Sharing

Objectives:

  • Communication: Networks allow users to send emails, messages, and video calls.
  • Resource Sharing: Users can share printers, files, and internet access.
  • Data Storage and Retrieval: Cloud storage helps store and retrieve data from anywhere.
  • Centralized Management: Large organizations manage data through servers efficiently.
  • Security and Access Control: Networks enable secure data access through authentication.

Examples of Resource Sharing:

  • A school shares one printer for all classrooms.
  • Offices store employee data on a shared database.
  • Students access online study materials through networked computers.

2. Simplex Communication – Time Calculation

Given:

  • Data Rate = 500 bps
  • Message Sizes: (a) 10 kilobits, (b) 10 kilobytes

(a) Transmission time for 10 kilobits Time=Total bits/Transmission Rate=10,000/500=20 seconds

(b) Transmission time for 10 kilobytes
1 Byte = 8 Bits → 10 KB = 10,000×8= 80,000 bits

Time=80,000/500=160 seconds=2 minutes 40 seconds


3. Packet Switching vs. Circuit Switching

Packet Switching

  • Data is divided into packets and sent through different routes.
  • Efficient use of bandwidth.
  • Used in the Internet (e.g., emails, web browsing).

Circuit Switching

  • A dedicated path is established for the whole communication.
  • More reliable but less efficient.
  • Used in traditional telephone systems.

4. Importance of Protocols and Key Protocols

Role of Protocols:

  • Standardize communication between devices.
  • Ensure data is transmitted accurately.
  • Manage error detection and correction.

Key Protocols:

  • TCP/IP: Manages internet communication.
  • HTTP: Transfers web pages.
  • DNS: Converts website names to IP addresses.
  • DHCP: Assigns IP addresses to devices.

5. Network Security Methods

  • Firewalls: Block unauthorized access to networks.
  • Encryption: Converts data into unreadable code to protect privacy.
  • Antivirus Software: Detects and removes malicious software.

6. Real-World Applications of Networks

  • Business: Online banking, e-commerce.
  • Education: E-learning platforms like Google Classroom.
  • Healthcare: Online patient records and telemedicine.

7. Comparison of Network Topologies

TopologyStructureAdvantagesDisadvantages
StarCentral hub connects devicesEasy troubleshootingFailure of hub affects all
RingEach device connected to two othersLess data collisionFailure of one node affects all
BusSingle central cableCost-effectiveSlow with high traffic
MeshEvery node connects to multiple othersHigh reliabilityExpensive to set up

8. Shift Cipher with Shift Amount = 4

Encryption:

SECURITY → WMXYVMI
(S → W, E → I, C → G, etc.)

Decryption:

WMXYVMI → SECURITY
(W → S, M → I, etc.)


9. IPv4 Address Calculation

(a) Total Unique IPv4 Addresses

IPv4 uses 32 bits, so the total addresses: 232=4,294,967,296

(b) Addresses Left After Reserving 10%

10%×4,294,967,296=429,496,729.6≈429,496,72910

Remaining=4,294,967,296−429,496,729=3,865,470,567