# Computer Fundamentals Questions and Answers – Universal Gates

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This set of Computer Fundamentals Multiple Choice Questions & Answers (MCQs) focuses on “Universal Gates”.

1. A ____________ is a circuit with only one output but can have multiple inputs.
a) Logic gate
b) Truth table
c) Binary circuit
d) Boolean circuit

Explanation: A logic gate is used to evaluate a Boolean expression.
It can have multiple inputs but can have only one output.
The different types of logic gates are AND, OR, NOT etc.

2. There are 5 universal gates.
a) True
b) False

Explanation: There are only 2 main universal gates: NAND and NOR.
A NAND gate as well as the NOR gate can be used to implement any other Boolean expression thus it is called as a universal gate.

3. The Output is LOW if any one of the inputs is HIGH in case of a _________ gate.
a) NOR
b) NAND
c) OR
d) AND

Explanation: In case of NOR Gate the Output is Low (i.e. 0) when any of the Input is High (i.e. 1).
TRUTH TABLE of NOR Gate:-

A B Output
0 0 1 (High)
0 1 0 (Low)
1 0 0 (Low)
1 1 0 (Low)
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This proves it.

4. The following figure shows a ___________ gate.

a) NOR
b) NAND
c) EXOR
d) OR

Explanation: The figure is that of a NOR gate.
The bubble signifies that it is a NOR gate.
It is a type of universal gate and can be used to implement all the boolean expressions.

5. The complement of the input given is obtained in case of:
a) NOR
b) AND+NOR
c) NOT
d) EX-OR

Explanation: The NOT gate, also called as the inverter gate is used to reverse the input which is given.
It gives an inverted output, thus gives the complement.
Expression for NOT gate: Y=A’, where A is the input.

6. How many AND gates are required to realize the following expression Y=AB+BC?
a) 4
b) 8
c) 1
d) 2

Explanation: 2 AND gates are required to realize the expression.
1 AND gate will be used to connect the inputs A and B whereas the other will be used to connect the inputs B and C.

7. Number of outputs in a half adder _____________
a) 1
b) 2
c) 3
d) 0

Explanation: A half adder gives two outputs.
One is called the sum and the other is carry.
Half adder can be implemented using an EXOR gate and an AND gate.

8. The ________ gate is an OR gate followed by a NOT gate.
a) NAND
b) EXOR
c) NOR
d) EXNOR

Explanation: A NOR gate is a universal gate which is an OR gate followed by a NOT gate.
It therefore reverses the output obtained by an OR gate.
It can be used to implement any Boolean expression.

9. The expression of a NAND gate is_______
a) A.B
b) A’B+AB’
c) (A.B)’
d) (A+B)’

Explanation: A NAND gate is an AND gate followed by a NOT gate.
It therefore inverts the output of an AND gate.
NAND gate is also a universal gate.

10. Which of the following correctly describes the distributive law.
a)( A+B)(C+D)=AB+CD
b) (A+B).C=AC+BC
c) (AB)(A+B)=AB
d) (A.B)C=AC.AB

Explanation: The second option correctly describes the distributive law.
(A+B).C =AC+BC.
Boolean Laws are used to implementing and simplifying Boolean expression.

Sanfoundry Global Education & Learning Series – Computer Fundamentals.

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