Digital Circuits Questions and Answers – Parity Generators/Checkers – 2

This set of Digital Electronic/Circuits online test focuses on “Parity Generators/Checkers – 2”.

1. Which error detection method uses one’s complement arithmetic?
a) Simple parity check
b) Two-dimensional parity check
c) CRC
d) Checksum

Explanation: A checksum is an error detection method used for the purpose of detecting errors that may have been incorporated during transmission. The checksum can be generated simply by adding bits. Hence, one’s complement arithmetic uses checksum.

2. Which error detection method consists of just one redundant bit per data unit?
a) Simple parity check
b) Two-dimensional parity check
c) CRC
d) Checksum

Explanation: A parity checker is an error detection method used for the purpose of detecting errors that may have been incorporated during transmission. Simple parity check method consists of just one redundant bit per data unit. It is again classified as even parity and odd parity.

3. How many types of parity bits are found?
a) 2
b) 3
c) 4
d) 1

Explanation: There are two types of parity bits, namely even parity and odd parity. In even parity, a 1 bit is added in order to make a group of data bits have even number of 1s. While, in odd parity, a 1 bit is added in order to make a group of data bits have odd number of 1s.

4. What is a parity bit?
a) An error detection is achieved by adding an extra bit
b) After addition, the carry is found
c) Bit generated during data transmission
d) After addition, the total number of bits

Explanation: A simple form of error detection is achieved by adding an extra bit to the transmitted word. The additional bit is known as parity bits.

5. The BCD number 101011 has _______ priority.
a) Even
b) Odd
c) Both even and odd
d) Undefined

Explanation: The given BCD number 101011 has even priority because it has an even number of 1’s (i.e. 4).
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6. Which error detection method involves polynomials?
a) Simple parity check
b) CRC
c) Two-dimensional parity check
d) Checksum

Explanation: Cyclic Redundancy Check(CRC) involves parity check polynomials. In the even parity case of CRC, the 1-bit is generated by checking the polynomial x+1.

7. The odd parity output of decimal number 9 is ___________
a) 0
b) 1
c) 1001
d) 0011

Explanation: The odd parity output of decimal number 9 is 1 because the BCD number for 9 is 1001 and it has even number of 1’s.

8. If odd parity is used for ASCII error detection, the number of 0s per 8-bit symbol is _______
a) Indeterminate
b) 42
c) Even
d) Odd

Explanation: Odd parity bit is 1 when the group of data bits consists of even number of 1s. So to make the group of data bits have odd number of 1s, 1 extra bit is added. If odd parity is used for ASCII error detection, the number of 0s per 8-bit symbol is indeterminate because it is applicable only for 6-bit symbol.

9. Which error detection method can detect a single-bit error?
a) Simple parity check
b) Two-dimensional parity check
c) CRC
d) Checksum

Explanation: A single-bit error can be detected by using two-dimensional parity check method. Since it converts the 4-bit number into 8-bit and count the number of one’s.

10. Which gates are ideal for checking the parity bits?
a) AND
b) NAND
c) EX-OR
d) EX-NOR

Explanation: Exclusive-OR gates are ideal for checking the parity of a binary number because they produce an output when the input has an odd number of 1’s. Therefore, an even-parity input to an EX-OR gate produces a low output, while an odd parity input produces a high output. While, in case of AND, it produces high output when all inputs are 1 else low. Whereas, NAND, does the opposite, by producing low output when all inputs are 1 else high.

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