**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 = 10

^{4}= 2

^{n}(where n is the number of bits required) = 2

^{13.29}. 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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