This set of Computer Organization and Architecture Multiple Choice Questions & Answers (MCQs) focuses on “Fast Adders”.

1. The logic operations are simpler to implement using logic circuits.
a) True
b) False

Explanation: The logic operation includes AND, OR, XOR etc.

2. The logic operations are implemented using _______ circuits.
a) Bridge
b) Logical
c) Combinatorial
d) Gate

Explanation: The combinatorial circuits means, using the basic universal gates.

3. The carry generation function: ci + 1 = yici + xici + xiyi, is implemented in ____________

Explanation: In this the carry for the next step is generated in the previous steps operation.

4. Which option is true regarding the carry in the ripple adders?
a) Are generated at the beginning only
b) Must travel through the configuration
c) Is generated at the end of each operation
d) None of the mentioned

Explanation: The carry must pass through the configuration of the circuit till it reaches the particular step.

5. In full adders the sum circuit is implemented using ________
a) And & or gates
b) NAND gate
c) XOR
d) XNOR

Explanation: sum = a ^ b ^ c (‘^’ indicates XOR operation).
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6. The usual implementation of the carry circuit involves _________
a) And & or gates
b) XOR
c) NAND
d) XNOR

Explanation: In case of full and half adders this method is used.

7. A _______ gate is used to detect the occurrence of an overflow.
a) NAND
b) XOR
c) XNOR
d) AND

Explanation: The overflow is detected by cn^cn-1 (‘^’ indicates XOR operation).

8. In a normal adder circuit, the delay obtained in a generation of the output is _______
a) 2n + 2
b) 2n
c) n + 2
d) None of the mentioned

Explanation: The 2n delay cause of the carry generation and the 2 delay cause of the XOR operation.

9. The final addition sum of the numbers, 0110 & 0110 is ____________
a) 1101
b) 1111
c) 1001
d) 1010

Explanation: None.

10. The delay reduced to in the carry look ahead adder is __________
a) 5
b) 8
c) 10
d) 2n

Explanation: None.

Sanfoundry Global Education & Learning Series – Computer Organisation and Architecture.

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