Question Bank — Data Communication

NCERT Class 12 Computer Science · Chapter 11 · CBSE Board Pattern

Class 12 Computer Science Chapter 11 Question Bank CBSE Board Pattern

Section A — MCQs (10 questions, 1 mark each)

1. The term Data Communication comprises which two words?
(a) Data and Network
(b) Data and Communication
(c) Sender and Receiver
(d) Message and Protocol

2. Which of the following is NOT a component of data communication?
(a) Sender
(b) Receiver
(c) Bandwidth
(d) Protocol

3. Bandwidth of a channel is measured in:
(a) bits per second
(b) Hertz (Hz)
(c) metres
(d) seconds

4. In which type of communication can both devices send and receive data simultaneously?
(a) Simplex
(b) Half-duplex
(c) Full-duplex
(d) Unidirectional

5. Which switching technique breaks the message into smaller pieces called packets?
(a) Circuit switching
(b) Packet switching
(c) Dedicated switching
(d) Mesh switching

6. Twisted pair cable, coaxial cable and optical fibre cable belong to which category of transmission media?
(a) Unguided media
(b) Wireless media
(c) Guided/wired media
(d) Infrared media

7. Which wireless technology is used for short-range communication (approx. 10 m) between devices such as headphones and keyboards?
(a) Wi-Fi
(b) Bluetooth
(c) WiMax
(d) 4G

8. HTTP stands for:
(a) HyperText Transfer Protocol
(b) High Transfer Text Protocol
(c) HyperText Transmission Protocol
(d) Hyper Transfer Text Protocol

9. Assertion-Reason

Assertion (A): In packet switching, different packets of the same message may take different routes.
Reason (R): A dedicated path is established between sender and receiver before communication begins.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

10. Assertion-Reason

Assertion (A): Optical fibre cable carries data in the form of light signals.
Reason (R): It uses a thin transparent strand of glass at the centre covered with cladding.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Section B — Very Short Answer (6 questions, 2 marks each)

1. Define the terms ‘sender’ and ‘receiver’ in the context of data communication.

2. Differentiate between simplex and half-duplex communication (any two points).

3. What is bandwidth? State its unit as given in the chapter.

4. State any two differences between guided and unguided transmission media.

5. What is a protocol? Give one example from the chapter.

6. Convert 18 Gbps into bits per second (show the steps using the conversion factors given in the chapter).

Section C — Short Answer (5 questions, 3 marks each)

1. Explain the three types of data communication (simplex, half-duplex and full-duplex) with one example of each.

2. Differentiate between circuit switching and packet switching (any three points).

3. The following calculation is given for finding data transfer rate. Identify the error and write the correct solution.
A user wants to upload 10 pages in 20 seconds. Assume 1 page = 1600 characters and each character = 8 bits. Calculate the required data rate.

4. List the three categories of wired transmission media. Write one feature of twisted-pair cable.

5. A composite signal contains frequencies between 500 MHz and 1 GHz. Calculate the bandwidth of the signal. Also state the unit of bandwidth.

Section D — Long Answer (3 questions, 5 marks each)

1. Explain the five components of data communication with the help of a labelled diagram (as described in the chapter).

2. Explain packet switching technique. Draw a trace table showing how a message divided into three packets travels from sender to receiver when packets may take different routes and are reassembled at the destination.

3. What is TCP/IP? Explain the role of IP and TCP in ensuring reliable delivery of data over the Internet.

Section E — Case/Source-Based (2 questions, 4 marks each)

Case 1

Riya wants to connect her laptop, smartphone and Bluetooth printer at home to access the Internet and share files. She uses a wireless router (access point) connected to a wired broadband connection.

(a) Identify the transmission media used between the router and Riya’s devices.
(b) Which protocol is primarily used to access web pages from her browser?
(c) Name the short-range wireless technology that allows her laptop to connect directly to the Bluetooth printer.
(d) State one advantage of using packet switching in this home network scenario.

Case 2

A student makes a voice call from a 4G mobile phone. The call is converted into digital packets that travel through the mobile network.

(a) Which generation of mobile technology is being used? State one feature of this generation.
(b) Name the switching technique most likely used for the voice call.
(c) Which component of data communication is represented by the mobile tower?
(d) Why is a protocol required when the call data moves between different networks?

▶ Answer Key Attempt all questions first,
then tap to reveal

Section A

  1. (b)
  2. (c)
  3. (b)
  4. (c)
  5. (b)
  6. (c)
  7. (b)
  8. (a)
  9. (c) — A is true; R describes circuit switching, hence false.
  10. (a) — Both true; R correctly explains how optical fibre carries light.

Section B

  1. Sender: device capable of sending data over network (e.g., computer, mobile). Receiver: device capable of receiving data (e.g., printer, laptop). (1+1)
  2. Simplex: unidirectional (one device only sends). Half-duplex: bidirectional but not simultaneous. (1+1)
  3. Bandwidth: range of frequencies available for transmission; measured in Hertz (Hz). (1+1)
  4. Guided: physical wired link; Unguided: electromagnetic waves through air (no physical link). (1+1)
  5. Protocol: set of rules followed by communicating parties for successful data exchange. Example: HTTP / TCP/IP. (1+1)
  6. 18 Gbps = 18 × 2³⁰ bps = 18 × 1 073 741 824 = 19 327 352 832 bps. (1+1+1)

Section C

  1. Simplex: one-way (keyboard to computer). Half-duplex: two-way but alternate (walkie-talkie). Full-duplex: simultaneous two-way (mobile phone). (1×3)
  2. Circuit: dedicated path established before transmission, all packets follow same path. Packet: message broken into packets, each may take different route, reassembled at destination. Channel occupied only during packet transmission in packet switching. (1×3)
  3. Error: calculation of total bits or division by time is missing/incorrect. Correct: Total bits = 10 × 1600 × 8 = 1 28 000 bits. Data rate = 1 28 000 / 20 = 6400 bps. (3)
  4. Twisted-pair, coaxial, optical fibre. Feature of twisted-pair: two copper wires twisted to minimise electrical interference; low cost. (2+1)
  5. Bandwidth = 1 GHz – 500 MHz = 500 MHz. Unit: Hertz (Hz). (2+1)

Section D

  1. Components: Sender, Receiver, Message, Communication media (transmission media), Protocols. Diagram shows flow from sender → media → receiver with protocol rules. (5 marking points)
  2. Packet switching explanation + trace table:
    Packet 1 (via Node A), Packet 2 (via Node B), Packet 3 (via Node A) → reassembly at receiver. (5)
    text Packet | Route | Status 1 | Node A | Arrived 2 | Node B | Arrived 3 | Node A | Arrived All packets reassembled into original message.
  3. TCP/IP: client-server model. IP assigns unique address to each node. TCP breaks data into packets, ensures ordered delivery and retransmission of lost packets. (5)

Section E

Case 1

(a) Wireless / unguided media (radio waves / Wi-Fi).
(b) HTTP.
(c) Bluetooth.
(d) Packets can take multiple available routes; efficient use of shared channel. (1×4)

Case 2

(a) 4G – supports interactive multimedia, faster data transfer than 3G.
(b) Packet switching.
(c) Receiver / intermediate node (or sender/receiver depending on direction).
(d) Different networks have varying speeds and formats; protocols ensure flow control, addressing and reliable delivery. (1×4)

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All questions are answerable from the NCERT chapter text. Reviewed by GFIS faculty.