Computer Science for IGCSE & O level - Data Transmission (Section 13)
1
Which of the following is a critical step in the automatic repeat request (ARQ) process?
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(B)
The receiver sends an acknowledgement to the sender if the data is successfully received.
2
What is the objective of an echo check in data communication?
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(B)
To verify that the data has been received correctly.
3
In the context of packet switching, what does the term 'node' refer to?
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(C)
A router in the network.
4
What is the role of the private key in asymmetric encryption?
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(C)
To decrypt data that has been encrypted with the corresponding public key
5
What does 'ciphertext' refer to in the context of data security?
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(C)
The encrypted form of the message.
6
What is the biggest disadvantage of parity checks?
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(B)
They can only detect some types of errors.
7
In odd parity, if a data byte is 11001100, what is the value of the parity bit?
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(A)
0
8
Which of the following is a purpose of a public key in asymmetric encryption?
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(C)
Shared with anyone who wants to send encrypted messages.
9
Which of the following is an example of symmetric-key cryptography?
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(B)
AES
10
What type of data transmission mode is used in a standard telephone call?
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(C)
Full-duplex
11
What is the main advantage of symmetric encryption?
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(A)
High speed.
12
What is the key benefit of using a digital signature?
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(C)
Non-repudiation and message authenticity
13
Which of the following uses the calculated value which is a sum of values of data, the receiving computer also calculates the value from the block of data and compares the values?
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(C)
Checksum
14
What is 'plaintext' in the context of cryptography?
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(C)
The original, unencrypted data.
15
Which of the following is a characteristic of packet switching?
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A
C
16
Which of the following is an example of a block-level error detection method?
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(D)
All of the above
17
Which of the following is a function of a check digit?
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(B)
To detect errors during transmission.
18
What are the functionalities of ARQ?
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A
B
C
19
Which key is primarily used to verify the sender's identity in the digital signature process using asymmetric encryption?
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(A)
The public key
20
Which mode of transmission is used in a CB radio?
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(B)
Half-duplex
21
In a data transmission system, what is the function of parity checking?
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(B)
To identify errors that may occur during transmission.
22
What is the purpose of a check sum in data transmission?
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(B)
To detect errors in the data during transmission
23
In the ISBN-13 example, what is the function of the check digit?
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(B)
To ensure the ISBN number is valid.
24
What is the role of the sender in automatic repeat request (ARQ)?
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(B)
To retransmit data if an error is detected.
25
What is the primary function of a 'hash' function?
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(B)
To create a unique 'fingerprint' of the data.
26
In encryption, which of the following is the term used to describe the message before it is encrypted?
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(B)
Plaintext
27
Which of the following is the correct name for a form of encryption in which both the sender and the recipient use the same key to encrypt and decrypt?
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(A)
Symmetric key encryption
28
How is the original data sequence restored when using packet switching?
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(B)
Using sequence numbers in the header.
29
Which type of encryption is known for its speed and simplicity?
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(B)
Symmetric encryption
30
What does the term 'node' refer to within the context of packet switching?
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(C)
A router or other intermediary device.
31
What is the main method used by ARQ to ensure reliable data transmission?
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(C)
Retransmission of data.
32
Which error detection method does not rely on the addition of extra bits to the original data?
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(B)
Checksum
33
In a network, what is the role of a 'router'?
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(A)
To connect multiple networks together.
34
What is the primary objective of encrypting data?
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(B)
To make data unreadable to unauthorized users.
35
What are the essential components of a data packet?
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A
B
C
36
What security goal is achieved through encryption?
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(A)
Confidentiality
37
Which is the purpose of the sequence number in the header of a packet?
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(C)
To ensure packets are reassembled in the correct order.
38
What does ARQ stand for in the context of data transmission?
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(C)
Automatic Repeat Request
39
What is the primary purpose of symmetric key encryption?
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(C)
To encrypt data using a single key
40
In data transmission, what is the primary function of a 'checksum'?
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(C)
To check for errors that might occur during transmission.
41
Which method is used to verify the integrity of data during transmission?
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(C)
Checksums
42
For what purpose are check digits used?
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(B)
Error detection during data entry or scanning.
43
In even parity, if a data byte has three 1s, what will the parity bit be?
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(B)
1
44
What is a characteristic of asymmetric encryption?
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(B)
It uses a key pair (public and private).
45
Who should have access to the private key in asymmetric encryption?
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(C)
The receiver of the encrypted message.
46
What is a key characteristic of the term 'ciphertext'?
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(C)
It is unreadable without the correct key.
47
How does a checksum help in data integrity?
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(C)
By verifying that the data hasn't been altered during transmission.
48
What is the core concept behind an echo check?
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(B)
To verify data accuracy.
49
What happens if the sender receives a negative acknowledgement (NAK) in ARQ?
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(B)
The data is retransmitted.
50
In symmetric encryption, what does the term 'key' refer to?
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(A)
A secret code used to encrypt and decrypt the data.
