IGCSE Computer Science Paper-1: Specimen Questions with Answers 123 - 124 of 164

Question 123

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Which technique is used to send more than one call over a single line.

Explanation

Image of The Multiplexer Divides

Image of the Multiplexer Divides

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Multiplexing technique is used for sending more than one call over a single line.

i) Over a shared medium the multiple analog or digital signals are combined into one signal.

ii) The Multiplexing encodes multiple carrier frequencies.

iii) In case of Multiplexing, the received receives the separate signals as compared to the sender. This process is known as demultiplexing.

iv) Synchronous time-division multiplexing, Asynchronous time-division multiplexing, interleaving time-division multiplexing, Statistical time-division multiplexing are the four time division multiplexing techniques.

Question 124

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Explain OSI Model and the different layers of it?

Explanation

OSI Model stands for Open System interconnection. It can be dined as the reference model which describes how exactly different applications will be communicating with each other over the Computer Network.

Image of The 7 Layers of Osi Model

Image of the 7 Layers of Osi Model

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i) Physical Layer: It is the first layer of OSI Model. It refers to the bit level transmission thereby supporting electrical or mechanical interfaces being connected to the physical medium w. r. t synchronized communication.

ii) Data Link Layer: In this layer the data packet are encoded and decoded into bits.

iii) Network Layer: This layer is responsible for providing data routing paths for network communication.

iv) Transport Layer: It is responsible for end to end communication over a network.

v) Session Layer: This layer is responsible provides the mechanism for opening, closing and managing a session between end-user application processes.

vi) Presentation Layer: This layer transforms data into Application layer format.

vii) Application Layer: This layer is responsible for process-to-process communication across an IP network.

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