Digital Circuits Questions and Answers – Binary Coded Decimal(BCD)

Digital Circuits Questions and Answers – Binary Coded Decimal(BCD)

This set of Digital Electronics/Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Binary Coded Decimal(BCD)”.

1. Binary coded decimal is a combination of __________
a) Two binary digits
b) Three binary digits
c) Four binary digits
d) Five binary digits

Answer: c
Explanation: Binary coded decimal is a combination of 4 binary digits. For example-8421.

2. The decimal number 10 is represented in its BCD form as __________
a) 10100000
b) 01010111
c) 00010000
d) 00101011

Answer: c
Explanation: The decimal number 10 is represented in its BCD form as 0001 0000, in accordance to 8421 for each of the two digits.

3. Add the two BCD numbers: 1001 + 0100 = ?
a) 10101111
b) 01010000
c) 00010011
d) 00101011

Answer: c
Explanation: Firstly, Add the 1001 and 0100. We get 1101 as output but it’s not in BCD form. So, we add 0110 (i.e. 6) with 1101. As a result we get 10011 and it’s BCD form is 0001 0011.

4. Carry out BCD subtraction for (68) – (61) using 10’s complement method.
a) 00000111
b) 01110000
c) 100000111
d) 011111000

Answer: a
Explanation: First the two numbers are converted into their respective BCD form using 8421 sequence. Then binary subtraction is carried out.

5. Code is a symbolic representation of __________ information.
a) Continuous
b) Discrete
c) Analog
d) Both continuous and discrete

Answer: b
Explanation: Code is a symbolic representation of discrete information, which may be present in the form of numbers, letters or physical quantities. Mostly, it is represented using a particular number system like decimal or binary and such like.

6. When numbers, letters or words are represented by a special group of symbols, this process is called __________
a) Decoding
b) Encoding
c) Digitizing
d) Inverting

Answer: b
Explanation: When numbers, letters or words are represented by a special group of symbols, this process is called encoding. Encoding in the sense of fetching the codes or words in a computer. It is done to secure the transmission of information.

7. A three digit decimal number requires ________ for representation in the conventional BCD format.
a) 3 bits
b) 6 bits
c) 12 bits
d) 24 bits

Answer: c
Explanation: The number of bits needed to represent a given decimal number is always greater than the number of bits required for a straight binary encoding of the same. Hence, a three digit decimal number requires 12 bits for representation in BCD format.

8. How many bits would be required to encode decimal numbers 0 to 9999 in straight binary codes?
a) 12
b) 14
c) 16
d) 18

Answer: c
Explanation: Total number of decimals to be represented = 10000 = 104 = 2n (where n is the number of bits required) = 213.29. Therefore, the number of bits required for straight binary encoding = 14.

9. The excess-3 code for 597 is given by __________
a) 100011001010
b) 100010100111
c) 010110010111
d) 010110101101

Answer: a
Explanation: The addition of ‘3’ to each digit yields the three new digits ‘8’, ’12’ and ’10’. Hence, the corresponding four-bit binary equivalents are 100011001010, in accordance to 8421 format.

10. The decimal equivalent of the excess-3 number 110010100011.01110101 is _____________
a) 970.42
b) 1253.75
c) 861.75
d) 1132.87

Answer: a
Explanation: The conversion of binary numbers into digits ‘1100’, ‘1010’, ‘0011’, ‘0111’ and ‘0101’ gives ’12’, ‘5’, ‘3’, ‘7’ and ‘5’ respectively. Hence, the decimal number is 970.42.

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