Class 11 Computer Science – Chapter 1: Computer Systems

Class 11 Computer Science

Chapter 1: Computer Systems – NCERT Exercise Solutoin


  • A computing device, also referred as computer, processes the input data as per given instructions to generate desired output.
  • Computer system has four physical components viz. (i) CPU, (ii) Primary Memory, (iii) Input Device and (iv) Output Devices. They are referred to as hardware of computer.
  • Computer system has two types of primary memories viz. (i) RAM, the volatile memory and
  • (ii) ROM, the non-volatile memory.
  • System bus is used to transfer data, addresses and control signals between components of the computer system.
  • A microprocessor is a small-sized electronic component inside a computer that performs basic arithmetic and logical operations on data.
  • Microcontroller is a small computing device which has a CPU, a fixed amount of RAM, ROM and other peripherals embedded on a single chip.
  • Software is a set of instructions written to achieve the desired tasks and are mainly categorised as system software, programming tools and application software.
  • Hardware of a computer cannot function on its own. It needs software to be operational or functional.
  • Operating system is an interface between the user and the computer and supervises the working of computer system, i.e., it monitors and controls the hardware and software of the computer system.

Chapter 1: Computer Systems – NCERT Exercise Solution

Exercise with Solutions

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

Answer: Operating System – An operating system is a system software, which provide interface between user and hardware.

Two Primary functions of Operating systems are –

  • Process Management
  • File Management
  • Storage Management
  • Print Management
  • Service Management
  • Security

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

Answer: A Language Translator program (Compiler / Interpreter) convert the High level language program into the machine language program, which understand by computer system. Without translation it is not possible to understand by computer system because computer understand only machine language i.e. 0 and 1.

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

Answer: Machine code is a binary language code, which is directly understand by computer system while source code is written any other language which a machine can not understand.

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

Answer: RAM stands for Random Access Memory. RAM is a primary memory, which is an essential component of computer system. Programs and data are loaded into the primary memory before processing. CPU directly interacts with the primary memory (RAM) to perform read / write operation.

Difference between RAM and ROM

  1. RAM is a volatile memory while ROM is a non-volatile memory.
  2. RAM is used to store data temporarily while computer is working. OS loads all necessary programs and data into RAM, while ROM is a permanent storage, it keep the BIOS information which helps in starting of computer.
  3. RAM allows both READ and WRITE operations, while ROM allows only READ operation (READ Only).

Question 5: What is the need for secondary memory?

Answer : Primary memory has limited storage capacity and is either volatile (RAM) or read-only (ROM).

Thus, a computer system needs auxiliary or secondary memory (storage) to permanently store data and instructions for future use.

The secondary memory is non-volatile and has larger storage capacity than primary memory. It is slower and cheaper than the main memory. But, it cannot be accessed directly by the CPU. Contents of secondary storage need to be first brought into the main memory for the CPU to access. Examples of secondary memory devices include Hard Disk Drive (HDD), CD/ DVD, Memory Card, SSD, etc.

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

Answer: With the help of Control bus different components of computers can communicate to each.

Control bus is used to communicate control signals between different components of a computer.

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

Answer: Block Diagram of Computer System is –

Input Unit(Device) :-  Input Unit (device) is use to send the data and instruction to the Computer System i.e. CPU. Generally Inputted data and instructions are stored in primary memory. Input unit convert the input data into a digital form that is understand by computer system.

Output Unit (Device) :- The device that receives data from a computer system for display, physical production i.e. print out, called output unit. Output unit receive the data in digital form which it convert into the human understandable form.

Central Processing Unit: CPU is the brain of computer system, which perform all processing task. Microprocessor is the main component of CPU, which perform all types of processing. CPU is divided into three sub units – Control Unit, Arithmetic and Logic Unit and Primary Memory.

Control Unit – It controls all the other units. Control unit send the control signals to all unit whenever it is required.

Arithmetic and Logic Unit – ALU perform arithmetical and logical calculations. Arithmetic means Addition, subtraction, multiplication and division. Logical means comparison like greater than, less than etc.

Primary Memory – Primary memory mainly use to store the working data and instructions.

Secondary Storage – Secondary storage is a permanent storage, which is used to store the data and software permanently for future use.

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

Answer : Primary role of System Bus to transferred the data between different components of

a computer system using physical wires. It is also called bus. For example, bus is used for data transfer between a USB port and hard disk or between a hard disk and main memory.

As the CPU may require to read data from main memory or write data to main memory, a data bus is bidirectional. Address bus is use to specify the address of memory location where read or write operation can be performed by CPU, so that it is unidirectional.

Question 9: Differentiate between proprietary software and freeware software. Name two software of each type.

Answer: Proprietary software is a software, which license we need to purchase from vendor while freeware software is freely available, we can download it from internet.


Proprietary Software – Windows 10, Microsoft Office, Tally, Adobe Photoshop

Freeware – Ubuntu, Libreoffice Writer, Mozilla Firefox

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

Answer : Microprocessor is a small-sized electronic component inside a computer that carries out various tasks involved in data processing as well as arithmetic and logical operations.

The microcontroller is a small computing device which has a CPU, a fixed amount of RAM, ROM and other peripherals all embedded on a single chip.

Difference :

Microprocessor is having only CPU on the chip, while Microcontroller having CPR, RAM, ROM and other peripherals on a single chip.

Because of the very small size of the microcontroller, it is embedded in another device or system to perform a specific functionality. Home appliances are designed for specific tasks only, hence by using Microcontrollers their size as well as cost is reduced.

Question 11 : Mention the different types of data that you deal with while browsing the internet.

Ans : Structured, Unstructured and Semi Structured.

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

• Newspaper

• Cricket Match Score

• HTML Page

• Patient records in a hospital


• Newspaper                                –       Unstructured

• Cricket Match Score                   –       Structured

• HTML Page                                –       Semi structured

• Patient records in a hospital       –       Structured

Name the input/output device used to do the following:

To output audio

To enter textual data

To make hard copy of a text file

To display the data or information

To enter audio-based command

To build 3D models

Question 13 :To assist a visually impaired individual in entering data


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 or Projector

To enter audio-based command      –       Mic

To build 3D models                        –       3 D Printer

To assist a visually impaired individual in entering data – Brail Keyboard

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




Text editor

Answer : a.     Compiler           –       Programming Tools

        b.     Assembler         –       Programming Tools

        c.      Ubuntu              –       System Software

        d.     Text Editor        –       Programming Tools /Application Software

Class 11 Computer Science – Chapter 1 : Computer System NCERT Book Solution

Explore Yourself

Question 1. Ask your teacher to help you locate any two device drivers installed on your computer.

Answer: Printer Device Driver, Scanner Device Driver, Audio Device Driver

Question 2. Write any two system software and two application software installed on your computer.

Answer: Windows 10, Utility Programs – Anti-virus Software, Disk Defragmenter, Programming Tools- Java Compiler & Python Interpreter

Question 3. Which microprocessor does your personal computer have? Which generation does it belong to?

Answer: Intel I3, 7th Generation

Question 4. What is the clock speed of your microprocessor?

Answer: 3.4GHz – 4.2GHz

Question 5. Name any two devices in your school or home that have a microcontroller.

Answer: Keyboard, mouse, washing machine, digital camera,

pendrive, remote controller, microwave

Question 6. Check the size of RAM and HDD of a computer in your school. Make a table and write their size in Bytes, Kilobytes, Megabytes and Gigabytes.

Answer: RAM Size   –      4GB         

                Gigabytes          –       4 GB

                Megabytes         –       4096 MB

                Kilobytes           –       4,194,304 KB

                Bytes                –       4,294,967,296 Bytes

        HDD  Size  –       1 TB

                Terabytes  –       1

                Gigabytes  –       1024 GB                                  or     210 GB

                Megabytes –       1024 x 1024 MB                        or     220 MB

                Kilobytes   –       1024 x 1024 x 1024 KB              or     230 MB

                Bytes        –       1024 x 1024 x 1024 x 1024 Byt or     240 Bytes

Question 7. List all secondary storage devices available at your school or home.

Answer: List of Secondary storage devices are –

                HDD, Pen Drive, CD,  DVD,

Question 8. Which operating system is installed on your computer at home or school?

Answer: Windows – 10

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