Digital Logic and Design MCQs with Answers
Practice important Digital Logic and Design MCQs with answers and explanations.
Multiple Choice Questions
Q381: In a BCD Adder, what happens if the result of the first Adder is a valid BCD number with no carry?
- A: The second Adder adds a 6
- B: The second Adder adds a 0
- C: The result is discarded
- D: The result is displayed without change
View Answer
B
Q382: What is the Boolean expression for detecting an invalid BCD number?
- A: S3S2 + S3S1
- B: S3S2 + S1S0
- C: S3S1 + S2S0
- D: S3S0 + S2S1
View Answer
A
Q383: How many 4-bit Parallel Adder Circuits are required for adding two BCD digits?
- A: One
- B: Two
- C: Three
- D: Four
View Answer
B
Q384: How is a 2-digit BCD Adder implemented?
- A: Using two 4-bit Parallel Adders and invalid BCD detector circuits
- B: Using a single 4-bit Parallel Adder
- C: Using an 8-bit Adder
- D: Using two 8-bit Adders
View Answer
A
Q385: What is the output of the 4-bit Adder when adding two BCD numbers if a Carry is generated?
- A: The result is valid and no further action is needed
- B: The result is adjusted by adding 6
- C: The result is invalid
- D: The result is adjusted by adding 0
View Answer
B
Q386: Which ICs are used in a 2-digit BCD Adder to handle invalid BCD digits?
- A: 74LS283
- B: 74LS00 and 74LS04
- C: 74LS08 and 74LS32
- D: 74LS02 and 74LS20
View Answer
A
Q387: How does subtraction work in digital systems using 2's complement?
- A: By taking the 1's complement and adding 1
- B: By directly subtracting the numbers
- C: By converting the number to its positive form
- D: By taking the 2's complement of the minuend
View Answer
A
Q388: In a 4-bit Adder/Subtracter unit, how is subtraction performed?
- A: By setting the Add/Subtract control to 0
- B: By setting the Add/Subtract control to 1
- C: By setting the Carry In to 0
- D: By using the AND gates only
View Answer
B
Q389: What is the function of the Carry In in a 4-bit Subtractor circuit?
- A: To provide the carry bit for addition
- B: To convert subtraction to addition
- C: To handle the 2's complement operation
- D: To adjust the result of subtraction
View Answer
C
Q390: How many 4-bit ALUs are needed to implement a 16-bit ALU?
- A: Two
- B: Four
- C: Eight
- D: Six
View Answer
B