Class 9 Computer Science – Chapter 1: Computer Systems

Board: Federal Board (FBISE)

Section I: Multiple Choice Questions (MCQs)

i. Which technology replaced vacuum tubes in second-generation computers?

a) Transistors
b) Integrated Circuits (ICs)
c) Microprocessors
d) Magnetic tapes

Correct Answer: a) Transistors

ii. What is the primary goal of fifth-generation computers?

a) Fast speed
b) Thinking power
c) Enhanced memory
d) Faster microprocessors

Correct Answer: b) Thinking power

iii. Which computer generation introduced the use of Integrated Circuits (ICs)?

a) First Generation
b) Second Generation
c) Third Generation
d) Fourth Generation

Correct Answer: c) Third Generation

iv. In which generation of computers was the microprocessor developed?

a) First Generation
b) Second Generation
c) Third Generation
d) Fourth Generation

Correct Answer: d) Fourth Generation

v. What is the function of the motherboard in a computer system?

a) To store and retrieve data permanently
b) To connect and integrate all hardware components
c) To perform mathematical calculations
d) To display output on a monitor

Correct Answer: b) To connect and integrate all hardware components

vi. Which component of the microprocessor controls the decision-making processes?

a) Arithmetic Logic Unit (ALU)
b) Control Unit (CU)
c) Memory Unit
d) Registers

Correct Answer: b) Control Unit (CU)

vii. Which type of memory retains data even when the computer is turned off?

a) RAM
b) ROM
c) Cache
d) Register

Correct Answer: b) ROM

viii. What is the main purpose of cache memory?

a) Store program instructions
b) Provide high-speed storage
c) Control input/output devices
d) Perform arithmetic operations

Correct Answer: b) Provide high-speed storage

ix. What is the smallest unit of memory in a digital computer?

a) Kilobyte
b) Bit
c) Byte
d) Megabyte

Correct Answer: b) Bit

x. Which memory type uses laser beams to read and write data?

a) RAM
b) Optical memory
c) Cache memory
d) ROM

Correct Answer: b) Optical memory

xi. What is the primary function of the buses in a computer’s memory system?

a) Control memory operations
b) Display graphics
c) Transmit data between components
d) Perform arithmetic operations

Correct Answer: c) Transmit data between components

xii. Which component of data communication converts the electrical signal into a suitable form for transmission?

a) Message
b) Medium
c) Protocol
d) Sender

Correct Answer: d) Sender

xiii. What is the primary function of the Presentation Layer in the OSI model?

a) Establishing connections between computers
b) Converting data into a standard format
c) Deciding the physical path of data
d) Sending data in both directions simultaneously

Correct Answer: b) Converting data into a standard format

xiv. In which network topology is data transmission unidirectional, like radio or television broadcasts?

a) Star Topology
b) Bus Topology
c) Mesh Topology
d) Ring Topology

Correct Answer: d) Ring Topology

xv. Which network architecture requires each computer to act as either a server or a client but not both simultaneously?

a) Client/Server Network
b) Peer-to-Peer Network
c) Metropolitan Area Network (MAN)
d) Wide Area Network (WAN)

Correct Answer: a) Client/Server Network

Section II: Short Response Questions (SRQs)

i. What is the primary goal of fifth-generation computers?

The primary goal of fifth-generation computers is to develop systems based on Artificial Intelligence (AI) capable of learning, reasoning, and making decisions. They aim to process natural human language and exhibit thinking power to solve complex problems autonomously.

ii. Differentiate between volatile and non-volatile memory.

Volatile memory, such as RAM, temporarily stores data and loses its contents when the power supply is turned off. In contrast, non-volatile memory, such as ROM and Flash memory, retains stored data even when the device is powered down.

iii. Show memory hierarchy with the help of a diagram.

The memory hierarchy, arranged from fastest and smallest to slowest and largest in capacity, is:

Registers → Cache Memory → Main Memory (RAM/ROM) → Magnetic/Optical Secondary Storage → Tertiary Storage (Cloud/Tape).

Registers are located directly inside the CPU. They provide the highest speed but have the smallest storage capacity.

iv. Why is the word size of a processor important, and how does it affect the computer’s performance?

Word size determines the amount of data a CPU can process at one time. It is typically measured in bits, such as 32-bit or 64-bit. A larger word size allows the processor to handle more data per operation and can improve processing capability and overall system performance.

v. Imagine you are building a custom computer for a friend. Give three considerations you would take into account for this computer.

1. Intended use: Determine whether the computer will be used for gaming, video editing, or basic office work to select a suitable CPU and GPU.

2. RAM and storage: Ensure adequate RAM capacity and suitable storage, such as an SSD or HDD, for smooth performance.

3. Hardware compatibility: Check the motherboard socket type, power supply wattage, and cooling requirements.

vi. You are a computer technician tasked with upgrading an older computer with a slow CPU. How might you improve its performance without replacing the entire CPU?

Performance can be improved by upgrading system RAM to support heavier multitasking workloads. Replacing an old mechanical hard drive with a high-speed Solid State Drive (SSD) can significantly reduce boot and application loading times. Additionally, cleaning unnecessary startup applications and applying fresh thermal paste to the CPU cooler can help restore optimal operating speeds.

vii. Your school is planning to purchase new printers for the computer lab. Give two advantages and disadvantages of impact and non-impact printers to help them make a decision.

• Impact printers: They are cost-effective for printing multi-part forms and carbon copies. However, they are noisy and produce lower print quality.

• Non-impact printers: Printers such as laser and inkjet printers operate quietly and produce high-resolution output. However, they generally have higher initial equipment and replacement consumable costs.

viii. What does OOP stand for, and which programming languages commonly use this paradigm?

OOP stands for Object-Oriented Programming. It is a programming paradigm that organizes software design around data and objects rather than only functions and logic. Common programming languages that support OOP include Java, C++, Python, and C#.

ix. Define “protocol” in the context of data communication.

A protocol is a standardized set of rules and conventions that govern how data is formatted, transmitted, and received across a network. It ensures that connected hardware devices and software programs can communicate and understand each other.

x. Define simplex, half-duplex, and full-duplex modes of communication with one example each.

• Simplex: Communication takes place in only one direction. Example: A keyboard sending data to a computer.

• Half-duplex: Communication takes place in both directions, but only one direction at a time. Example: Walkie-talkies.

• Full-duplex: Communication takes place in both directions simultaneously. Example: Telephone calls.

xi. What are start and stop bits, and where are they used in data transmission?

Start and stop bits are control bits added to data characters in asynchronous serial communication. The start bit alerts the receiver that a character is arriving, while the stop bit signals the completion of its transmission.

xii. How does a switch differ from a hub in a network?

A hub broadcasts incoming data to all connected ports without checking the destination. This can increase network traffic and create security risks.

A switch checks destination MAC addresses and forwards data to the specific port connected to the intended device. This improves bandwidth efficiency and reduces unnecessary network traffic.

xiii. How does asynchronous transmission differ from synchronous transmission?

Asynchronous transmission sends data characters individually at irregular intervals. It uses start and stop bits for synchronization.

Synchronous transmission transfers large blocks of data continuously at a synchronized clock rate without requiring individual start and stop bits for each character.

xiv. Give three limitations of a peer-to-peer network compared to a client/server network.

1. Peer-to-peer networks lack centralized administration, making security management and user access control difficult.

2. They have limited scalability, and performance may decrease as more computers join the network.

3. Data backups must be performed individually on each computer rather than being managed centrally.

xv. What is the role of the Application Layer in the OSI model?

The Application Layer provides an interface between software applications, such as web browsers and email clients, and network services. It supports services such as file transfers, electronic mail, and remote database access.

Section III: Extended Response Questions (ERQs)

Q1. Describe the evolution of computer generations from the first generation to the fifth generation, highlighting the key technological developments and their impact on computing.

1. First Generation (1940–1956) – Vacuum Tubes

Computers such as ENIAC and UNIVAC relied on thousands of fragile vacuum tubes for circuitry and magnetic drums for memory. They were massive in size, generated extreme heat, consumed enormous amounts of electricity, and broke down frequently.

2. Second Generation (1956–1963) – Transistors

Transistors replaced vacuum tubes, making computers significantly smaller, faster, cheaper, more energy-efficient, and more reliable. High-level programming languages such as FORTRAN and COBOL also emerged during this era.

3. Third Generation (1964–1971) – Integrated Circuits (ICs)

Transistors were miniaturized and placed onto silicon chips called Integrated Circuits (ICs). This development reduced computer size and cost while increasing processing speed, making computers accessible to a wider commercial market.

4. Fourth Generation (1971–Present) – Microprocessors

Large-Scale Integration (LSI) and Very-Large-Scale Integration (VLSI) placed entire CPUs onto single microchips. This era introduced personal computers (PCs), laptops, and the internet revolution, transforming modern society.

5. Fifth Generation (Present and Beyond) – Artificial Intelligence (AI)

Fifth-generation computers focus on Artificial Intelligence (AI), natural language processing, neural networks, and machine learning. They use advanced integration technologies and parallel processing to develop systems capable of human-like reasoning and decision-making.

Q2. Discuss the importance of both natural and artificial systems by providing examples of each type.

Natural Systems

Natural systems are biological, ecological, or physical entities created by nature without human intervention.

Examples include:

• The human nervous system

• Ecosystems

• Weather patterns

• The solar system

Natural systems are important because they sustain life on Earth, maintain ecological balance, regulate natural resources, and provide models for technological inventions. For example, artificial neural networks are inspired by the human brain.

Artificial Systems

Artificial systems are human-made structures designed to achieve specific goals or perform predefined tasks.

Examples include:

• Digital computers

• Transportation networks

• Software operating systems

• Automated industrial assembly lines

Artificial systems are important because they automate repetitive calculations, increase industrial productivity, expand global communication, and help solve complex computational problems.

Q3. Explain the fundamental components of network communication, and how they work together to facilitate data transfer.

Successful data communication relies on five fundamental components working together:

1. Message

The actual information being transmitted from the sender to the receiver. It may include data, text, audio, or video.

2. Sender

The device, such as a computer, phone, or sensor, that creates and transmits the data message across the network.

3. Receiver

The target device intended to accept and process the incoming message.

4. Transmission Medium

The physical or wireless path through which data travels from the sender to the receiver. Examples include twisted-pair copper cables, fibre-optic cables, and radio waves.

5. Protocol

A formal set of rules governing how data is packaged, addressed, transmitted, routed, and received across network devices.

How They Work Together

The sender encodes the message into signals, formats it according to established protocols, and transmits it through the communication medium. The medium carries the signals to the destination receiver, where the protocol rules are used to interpret the data and reconstruct the original message.

Q4. Describe the roles of common communication devices like hubs, switches, routers, and gateways in data communication. How do they contribute to the functionality of a network?

1. Hubs

Hubs are basic networking devices that connect multiple computers in a Local Area Network (LAN). When data arrives at one port, the hub broadcasts it to all other ports. This can increase network traffic and reduce security.

2. Switches

Switches are intelligent networking devices that maintain a table of connected MAC addresses. Instead of broadcasting data to every device, a switch filters and forwards data directly to the intended destination port, improving bandwidth efficiency.

3. Routers

Routers operate at the network layer and connect different networks, such as connecting a home network to the Internet. They use IP addresses to determine where data packets should be forwarded.

4. Gateways

Gateways act as protocol translators between different network architectures or systems. They allow otherwise incompatible networks to exchange data successfully.

Q5. Discuss the advantages and limitations of different network topologies, including bus, star, and ring. When should each topology be used in a network design?

1. Bus Topology

Advantages:

• Simple to set up.

• Requires minimal cable length.

• Cost-effective for small networks.

Limitations:

• If the main cable (backbone) breaks, the entire network stops working.

• Troubleshooting is difficult.

Best Used For: Small, temporary, or low-cost networks where cabling costs must be minimized.

2. Star Topology

Advantages:

• If one cable fails, only the connected device is disconnected.

• Easy to add or remove devices.

• Troubleshooting can be performed centrally.

Limitations:

• Requires more cabling.

• If the central hub or switch fails, the entire network stops working.

Best Used For: Modern Local Area Networks (LANs) in offices, schools, and homes because of their high performance and ease of management.

3. Ring Topology

Advantages:

• Provides equal access to all computers.

• In token-based ring networks, data collisions are avoided because tokens circulate in one direction.

Limitations:

• A break in the ring cable can disrupt the entire network.

• Adding or removing devices can disrupt network operation.

Best Used For: Specialized industrial or campus token-ring networks that require predictable data delivery.

Q6. What is the OSI model, and how does it help in understanding the process of data communication? Give the purpose of each OSI layer.

The Open Systems Interconnection (OSI) model is a conceptual seven-layer framework developed by the International Organization for Standardization (ISO). It standardizes how different communication systems interact and exchange data, regardless of their underlying hardware architecture.

The Seven Layers and Their Purposes

1. Physical Layer

Manages the transmission of raw bits over physical communication media.

2. Data Link Layer

Handles node-to-node data transfer, framing, and physical addressing through MAC addresses.

3. Network Layer

Responsible for logical addressing through IP addresses and routing packets across multiple networks.

4. Transport Layer

Ensures reliable end-to-end data delivery, error control, flow control, and sequencing.

5. Session Layer

Establishes, manages, and terminates communication sessions between applications.

6. Presentation Layer

Handles data translation, formatting, encryption, and compression.

7. Application Layer

Provides network services and protocols, such as HTTP, FTP, and SMTP, to end-user software applications.

Q7. Discuss any three common applications of the Internet and their impact on society, including communication, education, business, entertainment, and research.

1. Communication (Email, VoIP, Social Media)

The Internet has transformed global communication by removing geographical barriers. Email, instant messaging, and video conferencing allow families, businesses, and governments to exchange information quickly and communicate in real time.

2. Education (E-Learning and Online Research)

Digital learning platforms, online universities, virtual classrooms, and open-access research libraries have made education more accessible. Students worldwide can access lectures, textbooks, and collaborative learning tools from different locations, transforming traditional classroom learning.

3. E-Commerce and Business

The Internet has created global digital marketplaces through e-commerce platforms, cloud computing, and online banking. Businesses can operate around the clock, reach customers worldwide, reduce operational costs, and improve supply chain management.

Notes by Sir Dilawar

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