NCERT Solutions for Class 12 Computer Science Chapter 11 Data Communication

Exercise Solutions: NCERT Solutions Class 12 Computer Science Chapter 11 Data Communication (2025-26)

1. What is data communication? What are the main components of data communication?

   Answer: Data communication refers to the exchange of data between two or more networked or connected devices. The main components of data communication are sender, receiver, communication medium (also known as transmission media), the message to be communicated, and certain rules or protocols to be followed during communication.

2. Which communication mode allows communication in both directions simultaneously?

   Answer: Full-duplex communication mode enables communication in both directions simultaneously.

3. Among LAN, MAN, and WAN, which has the highest speed and which one can cover the largest area?

   Answer: LAN (Local Area Network) offers the highest speed, while WAN (Wide Area Network) covers the largest area.

4. What are three categories of wired media? Explain them.

   Answer:

   • Twisted Pair Cable: Consists of two insulated copper wires twisted together to minimize interference. Used in telephone lines and LANs. Types: Unshielded (UTP) and Shielded (STP).
   • Coaxial Cable: Has a central copper core insulated and covered by an outer conductor (copper mesh) and a plastic cover. Offers better shielding and is used for higher frequency signals over longer distances.
   • Optical Fiber: Carries data as light within a glass fiber, using refraction. High bandwidth, light-weight, immune to electromagnetic interference, but expensive and usually unidirectional (two cables needed for full-duplex).

5. Compare wired and wireless media.

   Answer:

   Wired Media (Guided)	Wireless Media (Unguided)
   Physical cables (twisted pair, coaxial, fiber-optic) provide the path for data signals. More secure and stable but less flexible for mobility.	Uses electromagnetic waves through air (radio, microwave, infrared). Suitable for mobile and remote access but more prone to interference.
   Installation and expansion may be costly.	Easy to set up and expand, especially in large areas.

6. Which transmission media carries signals in the form of light?

   Answer: Optical Fiber transmission media carries signals in the form of light.

7. List out the advantages and disadvantages of optical fiber cable.

   Answer:

   • Advantages:
     • High bandwidth and faster data transfer rates.
     • Light-weight and immune to electromagnetic interference.
     • Signals can travel long distances without much loss.
   • Disadvantages:
     • Expensive compared to other cables.
     • Unidirectional—needs two cables for full-duplex communication.
     • Requires specialized installation and maintenance.

8. What is the range of frequency for radio waves?

   Answer: The range of frequency for radio waves is between 3 KHz to 1 GHz.

9. 18 Gbps is equal to how many bits per second?

   Answer: 1 Gbps = 1,000,000,000 bits per second.
   So, 18 Gbps = 18 × 1,000,000,000 = 18,000,000,000 bits per second.

10. HTTP stands for?

    Answer: HTTP stands for HyperText Transfer Protocol.

11. Write short note on the following:

    • a) HTTP
      Answer: HTTP (HyperText Transfer Protocol) is the primary protocol used for accessing the World Wide Web. It follows a client-server model, where requests are sent by clients (browsers) and responses are given by servers. HTTP defines the way information is formatted and transferred online.
    • b) Bandwidth
      Answer: Bandwidth is the range of frequencies available for transmitting data through a channel. It is measured in Hertz (Hz). Higher bandwidth allows more data to be transferred per second.
    • c) Bluetooth
      Answer: Bluetooth is a short-range wireless technology used to connect electronic devices (like phones, headphones, keyboards, printers) within about 10 meters at 1–2 Mbps. It creates a personal area network and is commonly used for wireless data exchange.
    • d) DNS
      Answer: DNS (Domain Name System) is the naming system of the internet. It maps domain names (like google.com) to their corresponding IP addresses, making web navigation easier by allowing users to use readable names instead of numbers.
    • e) Data transfer rate
      Answer: Data transfer rate, or bit rate, is the number of bits transmitted between source and destination per second. It is measured in bits per second (bps). Higher transfer rates allow faster data communication.

12. What is protocol in data communication? Explain with an example.

    Answer: In data communication, a protocol is a set of standard rules that the communicating parties (sender, receiver, and intermediates) must follow for successful and reliable data exchange.
    Example: In the TCP/IP protocol, TCP handles reliable delivery and sequencing of packets, while IP manages addressing and routing. For instance, when sending an email, TCP ensures proper packet sequence and delivery, and IP routes the packets to the correct destination.

13. A composite signal contains frequencies between 500 MHz and 1 GHz. What is the bandwidth of a signal?

    Answer: Bandwidth = Maximum frequency – Minimum frequency
    = 1 GHz − 500 MHz = 1,000,000,000 Hz − 500,000,000 Hz = 500,000,000 Hz = 500 MHz.
    Therefore, the bandwidth of the composite signal is 500 MHz.

Mastering Data Communication in Class 12 Computer Science

Understanding data communication basics is crucial for excelling in NCERT Solutions Class 12 Computer Science Chapter 11. Grasp how information flows between devices, including the roles of sender, receiver, and protocols, to build strong conceptual clarity for your board exams.

Explore transmission media and switching techniques to boost your understanding. Pay special attention to differences between wired and wireless technologies—this is often asked in practical as well as theory questions for the 2025-26 curriculum.

Consistent practice of exercise-based solutions ensures deep comprehension. Review each key term—like bandwidth and protocols—and create quick notes. This method helps you revise effectively and boosts your chances of securing top marks in the exam.