Class 11 Computer Science Chapter 1: Computer System – NCERT Solutions

NCERT Solutions for Computer Science Chapter 1: Computer System (2025-26)

1. Name the software required to make a computer functional. Write down its two primary services.

Answer: The software required to make a computer functional is the Operating System (OS). Its two primary services are:
(1) Managing hardware resources of the computer (such as CPU, memory, and devices).
(2) Providing an interface between the user and the computer hardware, allowing users to interact with the system.

2. How does the computer understand a program written in high level language?

Answer: A computer cannot directly understand programs written in high-level languages. To execute these programs, special software called language translators (compiler, interpreter, or assembler) is used to convert high-level language code into machine language (binary code) which can be understood and processed by the computer.

3. Why is the execution time of the machine code less than that of source code?

Answer: Source code (written in high-level or assembly language) must be translated into machine code before execution. Executing machine code is faster because it is directly understood by the computer's CPU, eliminating the need for translation during execution, thus reducing execution time.

4. What is the need of RAM? How does it differ from ROM?

Answer: RAM (Random Access Memory) is essential for storing data and instructions temporarily while the computer is working, enabling quick access by the CPU. The difference between RAM and ROM is:

• RAM is volatile memory: its contents are lost when power is switched off. It temporarily holds data for processing.
• ROM (Read Only Memory) is non-volatile memory: it permanently stores instructions required to start the computer.

5. What is the need for secondary memory?

Answer: Secondary memory (such as HDD, SSD, CD/DVD, and pen drives) is needed to store data, instructions, and results permanently for future use. Unlike primary memory which is volatile, secondary memory retains information even when the power is switched off.

6. How do different components of the computer communicate with each other?

Answer: Different components of the computer communicate with each other using buses. There are three types of buses: data bus (transfers data bidirectionally), address bus (carries addresses unidirectionally), and control bus (transfers control signals unidirectionally) that connect the CPU, memory, and input/output devices.

7. Draw the block diagram of a computer system. Briefly write about the functionality of each component.

Answer: The block diagram of a computer system includes:

• CPU (Central Processing Unit): Performs arithmetic and logical operations; consists of ALU and CU.
• Memory: Stores data and instructions temporarily (primary) or permanently (secondary).
• Input Devices: Used to input data and commands (e.g., keyboard, mouse).
• Output Devices: Display or produce output (e.g., monitor, printer).
• Storage Devices: Retain data and programs (e.g., hard disk, SSD).

8. What is the primary role of system bus? Why is data bus bidirectional while address bus is unidirectional?

Answer: The primary role of the system bus is to provide a communication path between different components like CPU, memory, and I/O devices. The data bus is bidirectional as data can flow both to and from the CPU, whereas the address bus is unidirectional because memory addresses are sent in one direction (from CPU to memory or I/O).

9. Differentiate between proprietary software and freeware software. Name two software for each type.

Answer:

• Proprietary software: Software whose source code is not available to users and usually requires purchase or license. Examples: Microsoft Windows, Adobe Photoshop.
• Freeware software: Software that is free to use, but source code is not made public. Examples: Adobe Acrobat Reader, Skype.

10. Write the main difference between microcontroller and microprocessor. Why do smart home appliances have a microcontroller instead of microprocessor embedded in them?

Answer: A microprocessor contains only a CPU, while a microcontroller integrates CPU, RAM, ROM, and peripherals on a single chip. Smart home appliances use microcontrollers because they are compact, economical, and designed for dedicated control tasks within embedded systems.

11. Mention the different types of data that you deal with while browsing the Internet.

Answer: While browsing the Internet, you deal with multiple types of data, including:

• Structured data (like tables, databases),
• Semi-structured data (like emails, HTML pages),
• Unstructured data (like images, videos, social media posts).

12. Categorise the following data as structured, semi-structured and unstructured:

• Newspaper – Unstructured
• Cricket Match Score – Structured
• HTML Page – Semi-structured
• Patient records in a hospital – Structured

13. Name the input or output device used to do the following:

• To output audio – Speaker
• To enter textual data – Keyboard
• To make hard copy of a text file – Printer
• To display the data or information – Monitor
• To enter audio-based command – Microphone
• To build 3D models – 3D printer
• To assist a visually-impaired individual in entering data – Braille keyboard

14. Identify the category (system, application, programming tool) of the following software:

• Compiler – Programming Tool
• Assembler – Programming Tool
• Ubuntu – System Software
• Text editor – Application Software / Programming Tool

Mastering Computer System Concepts in NCERT Computer Science

A strong foundation in Computer System fundamentals is essential for success in Class 11 Computer Science. This chapter covers essential topics like CPU, memory, software, and operating systems, enabling students to effortlessly understand complex computing processes.

Regular revision of types of memory, data transfer, and software classifications ensures better conceptual clarity. Use easy-to-understand NCERT content and diagrams to visualize how different computer components interact in real-world scenarios.

Focus on practicing exercise questions and reviewing important tables for exams. Strengthen your understanding of primary and secondary memory, microprocessors, and application software for higher scores in school and competitive exams.