Important Questions and Answers for Class 12 Computer Science Chapter 11 Data Communication | 2026-27

The Class 12 Computer Science Chapter 11 Data Communication Important Question PDF helps students revise communication components, data transmission modes, wired and wireless media, switching techniques, and protocols. 

By practising these questions and reviewing the answers, students can identify topics that need more attention and improve their answer-writing skills.

Class 12 Computer Science Chapter 11 Multiple Choice Questions

Q1. Which is NOT one of the five main components of data communication?

(a) Sender

(b) Receiver

(c) Protocol

(d) Compiler

Answer: (d) Compiler. 

2. What is the unit used to measure bandwidth?

(a) Hertz

(b) Bits

(c) Seconds

(d) Bytes

Answer: (a) Hertz. Bandwidth is a range of frequencies.

Q3. In which communication mode can both devices transmit at the same time?

(a) Simplex

(b) Half-duplex

(c) Full-duplex

(d) One-way

Answer: (c) Full-duplex. Both devices can send and receive simultaneously

Q4. Which example represents half-duplex communication?

(a) Keyboard to computer

(b) Walkie-talkie

(c) Mobile phone conversation

(d) Television broadcast

Answer: (b) Walkie-talkie. Either party can speak, but not both simultaneously.

Q5. In packet switching, a message is divided into smaller units called:

(a) Channels

(b) Frequencies

(c) Packets

(d) Antennas

Answer: (c) Packets. These are sent independently and reassembled at the destination

Q6. Which wired medium transmits data in the form of light?

(a) Twisted-pair cable

(b) Coaxial cable

(c) Optical fibre

(d) Ethernet copper cable

Answer: (c) Optical fibre. It uses light travelling through a thin glass fibre.

Q7. Which of these electromagnetic waves generally needs line-of-sight transmission?

(a) Microwaves

(b) Low-frequency radio waves

(c) Infrared only through walls

(d) None of these

Answer: (a) Microwaves. Antennas must be directed towards one another.

Q8. Which IEEE standard is associated with Wi-Fi?

(a) 802.11

(b) 802.3

(c) 802.15 only

(d) 801.11

Answer: (a) 802.11.

Q9. Which mobile network generation introduced SMS and MMS services?

(a) 1G

(b) 2G

(c) 3G

(d) 4G

Answer: (b) 2G. It used digital voice communication and supported messaging.

Q10. Which protocol is mainly used to send email messages?

(a) FTP

(b) SMTP

(c) HTTP

(d) PPP

Answer: (b) SMTP. Simple Mail Transfer Protocol is used in email services

Class 12 Computer Science Chapter 11 Very Short Answer Questions

Q11. Define data communication.

Answer:

Data communication is the exchange of data, such as text, images, audio or video, between two or more connected devices through a communication medium.

Q12. Name the five components of data communication.

Answer: 

Sender, receiver, message, communication or transmission medium, and protocol.

Q13. What is the data transfer rate? State its unit.

Answer: 

Data transfer rate (bit rate) is the number of bits transmitted from source to destination in one second. It is measured in bits per second (bps).

Q14. What is a piconet?

Answer: 

A piconet is a short-range personal area network formed by Bluetooth-enabled devices.

Q15. Expand HTTP and FTP.

Answer: 

HTTP: HyperText Transfer Protocol. 

FTP: File Transfer Protocol.

Q16. What is an access point (AP) in a wireless LAN?

Answer: 

An access point connects wireless devices to a wired network and helps create a wireless local area network.

Q17. State one purpose of flow control in data communication. 

Answer: 

Flow control adjusts transmission when sender and receiver operate at different speeds, helping prevent data loss. 

Class 12 Computer Science Chapter 11 Short Answer Questions

Q18. Differentiate between bandwidth and data transfer rate. 

Answer: 

Bandwidth: The range of frequencies a channel can carry; measured in hertz (Hz). 

Data transfer rate: The number of bits sent per second; measured in bps. A channel with greater bandwidth generally supports a higher data transfer rate. 

Q19. Distinguish among simplex, half-duplex and full-duplex communication with one example each. 

Answer: 

• Simplex: Data moves in only one direction; example: keyboard input. 

• Half-duplex: Data can move both ways, but only one direction at a time; example: walkie-talkie. 

• Full-duplex: Data moves both ways simultaneously; example: a telephone conversation. 

Q20. How does packet switching differ from circuit switching? 

Answer:

• Circuit switching: A dedicated path is established before transmission; all packets follow it. 

• Packet switching: The message is split into packets that may travel via different routes. A channel is occupied only during packet transmission, and packets are assembled at the destination. 

Q21. Explain how twisted-pair cables reduce interference. Also name their two types. 

Answer: 

Two insulated copper wires are twisted together, which reduces electrical interference from nearby pairs. 

The types are, 

• UTP (Unshielded Twisted Pair)

• STP (Shielded Twisted Pair). 

Q22. State two advantages and one disadvantage of optical fibre. 

Answer:

• Advantages: High bandwidth and longer transmission distance; it is also unaffected by electromagnetic noise. 

• Disadvantage: It is expensive. Also the separate fibres are required for full-duplex communication. 

Q23. Differentiate between Bluetooth and Wi-Fi as discussed in the chapter.

Answer: 

• Bluetooth: Short-range wireless connectivity, commonly between personal devices such as headphones, keyboards and phones; a typical range is about 10 metres. 

• Wi-Fi: Wireless LAN technology (IEEE 802.11) used to connect devices through an access point to a local network and the Internet.

Q24. Why are communication protocols needed? Explain access control. 

Answer: 

Protocols provide common rules for reliable exchange, including flow control, addressing, data format, delivery and packet ordering. 

Access control decides which node can use a shared communication link at a given time, helping prevent collisions. 

Q25. A signal has frequency components from 500 MHz to 1 GHz. Calculate its bandwidth. 

Answer: 

Formula: Bandwidth = highest frequency - lowest frequency. Since 1 GHz = 1000 MHz, bandwidth = 1000 - 500 = 500 MHz. 

Class 12 Computer Science Chapter 11 Long Answer Questions

Q26. Describe the components of data communication with an example. 

Answer: 

Five components work together: 

(1) Sender - the device sending information; 

(2) Receiver - the device receiving it; 

(3) Message - the actual data, such as text, audio or an image; 

(4) Transmission medium - the wired or wireless path carrying the message; 

(5) Protocol - the shared rules for successful transmission. 

Example: When a student sends a document from a laptop to a network printer, the laptop is the sender, the printer is the receiver, the document is the message, the cable or Wi-Fi is the medium, and protocols govern communication. 

Q27. Compare the three guided transmission media covered in the chapter. 

Answer: 

• Twisted-pair cable: Consists of insulated copper wires twisted in pairs; inexpensive and common in telephone lines and LANs; twisting minimises interference. 

• Coaxial cable: Has a copper core, insulation, braided outer conductor and plastic cover; better shielded and supports higher bandwidth than twisted pair. 

• Optical fibre: Carries light through a thin glass fibre surrounded by cladding; lightweight, high bandwidth, longer reach and resistant to electromagnetic interference, but costly. The first two carry electrical signals, while optical fibre carries light.

Q28. Explain the classification of wireless transmission waves with their properties and uses. 

Answer: 

• Radio waves (3 kHz-1 GHz): Omnidirectional and susceptible to interference; used in AM/FM radio, television and cordless phones.

• Microwaves (1-300 GHz): Directional, require line-of-sight and cannot pass through hills or walls; used for radar and satellite links. 

• Infrared waves (300 GHz-400 THz): Short-distance communication; cannot pass through walls; used in remote controls and nearby devices. 

Q29. Explain the development of mobile communication from 1G to 5G. 

Answer: 

1G: Used analog signals for voice calls. 

2G: Introduced digital voice, improved quality and security, and SMS/MMS. 

3G: Provided both digital voice and mobile data/Internet services at faster speeds. 

4G: Supported much faster wireless broadband, voice, video and interactive multimedia. 

5G: It is a faster generation intended to support high-speed data, IoT, connected vehicles and machine-to-machine communication. These stages show the shift from basic analog voice to advanced mobile data. 

Q30. Explain the roles of HTTP, FTP, PPP, SMTP and TCP/IP in data communication. 

Answer: 

• HTTP: Request-response protocol used between a browser and web server to access web pages. 

• FTP: Transfers files between computers using a client-server model. 

• PPP: Establishes a direct, dedicated point-to-point link and can authenticate communicating devices. 

• SMTP: Sends email using message-header information and outgoing-mail queues. 

• TCP/IP: Provides Internet communication rules; IP identifies nodes using addresses, while TCP manages packet delivery and ordering. Each protocol serves a specific communication purpose. 

Key Data Communication Concepts to Revise Before Your Class 12 Computer Science Exam

Before attempting Chapter 11 important questions, students should practice the basic concepts of Data Communication. Pay special attention to definitions, differences between communication methods, and the functions of protocols, as these concepts help in answering different types of questions.

Important Exam Preparation Tips:

• Learn the five components of data communication with their functions.

• Practise differences between simplex, half-duplex, and full-duplex modes.

• Understand how circuit switching differs from packet switching.

• Revise the characteristics of wired and wireless transmission media.

• Remember the full forms and uses of important communication protocols.

• Practise numerical questions on data transfer rate and draw labelled diagrams wherever required.

How Vedantu's Class 12 Computer Science Chapter 11 Important Questions Help Students

Vedantu's Class 12 Computer Science Chapter 11 Important Questions are designed to help students practise Data Communication concepts in a structured way. Instead of only memorising definitions, students can use these questions to check their understanding and learn how to explain technical concepts in simple words.

The chapter-wise question-and-answer format helps students:

• Strengthen Conceptual Understanding: Understand how devices exchange information using communication channels and protocols.

• Improve Answer Writing: Practise clear definitions, comparisons, and detailed explanations for different question types.

• Identify Weak Areas: Recognise concepts that need more revision, such as transmission modes, switching techniques, or protocols.

• Prepare for Different Questions: Build confidence in answering MCQs, very short, short, and long answer questions.

• Revise More Effectively: Use the important questions and answers to review Chapter 11 concepts before school assessments and exams.

Students should first attempt each question independently and then compare their responses with the provided answers. This practice can help them improve accuracy, remember important concepts, and prepare more confidently for Computer Science exams.

Important Study Material Links for Class 12 Computer Science Chapter 11 Data Communication

Class 12 Computer Science Chapter-Wise Important Questions

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