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420+ Digital Electronics Solved MCQs

These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering , Bachelor of Science in Computer Science FY (BSc CS) , Bachelor of Computer Applications (BCA) , Bachelor of Science in Computer Science (BSc CS) .

101.

DeMorgan’s theorem states that                    

A. (ab)’ = a’ + b’
B. (a + b)’ = a’ * b
C. a’ + b’ = a’b’
D. (ab)’ = a’ + b
Answer» A. (ab)’ = a’ + b’
102.

(A + B)(A’ * B’) = ?

A. 1
B. 0
C. ab
D. ab’
Answer» B. 0
103.

Complement of the expression A’B + CD’ is                    

A. (a’ + b)(c’ + d)
B. (a + b’)(c’ + d)
C. (a’ + b)(c’ + d)
D. (a + b’)(c + d’)
Answer» B. (a + b’)(c’ + d)
104.

Simplify Y = AB’ + (A’ + B)C.

A. ab’ + c
B. ab + ac
C. a’b + ac’
D. ab + a
Answer» A. ab’ + c
105.

The boolean function A + BC is a reduced form of                          

A. ab + bc
B. (a + b)(a + c)
C. a’b + ab’c
D. (a + c)b
Answer» B. (a + b)(a + c)
106.

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
Answer» A. logic gate
107.

There are 5 universal gates.

A. true
B. false
Answer» B. false
108.

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
Answer» B. nand
109.

The complement of the input given is obtained in case of:

A. nor
B. and+nor
C. not
D. ex-or
Answer» C. not
110.

How many AND gates are required to realize the following expression Y=AB+BC?

A. 4
B. 8
C. 1
D. 2
Answer» D. 2
111.

Number of outputs in a half adder

A. 1
B. 2
C. 3
D. 0
Answer» B. 2
112.

The                  gate is an OR gate followed by a NOT gate.

A. nand
B. exor
C. nor
D. exnor
Answer» C. nor
113.

The expression of a NAND gate is               

A. a.b
B. a’b+ab’
C. (a.b)’
D. (a+b)’
Answer» C. (a.b)’
114.

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
Answer» B. (a+b).c=ac+bc
115.

The logical sum of two or more logical product terms is called                      

A. sop
B. pos
C. or operation
D. nand operation
Answer» A. sop
116.

The expression Y=(A+B)(B+C)(C+A) shows the                    operation.

A. and
B. pos
C. sop
D. nand
Answer» B. pos
117.

The canonical sum of product form of the function y(A,B) = A + B is                      

A. ab + bb + a’a
B. ab + ab’ + a’b
C. ba + ba’ + a’b’
D. ab’ + a’b + a’b’
Answer» B. ab + ab’ + a’b
118.

A variable on its own or in its complemented form is known as a

A. product term
B. literal
C. sum term
D. word
Answer» B. literal
119.

Maxterm is the sum of                      of the corresponding Minterm with its literal complemented.

A. terms
B. words
C. numbers
D. nibble
Answer» A. terms
120.

Canonical form is a unique way of representing                          

A. sop
B. minterm
C. boolean expressions
D. pos
Answer» C. boolean expressions
121.

There are                            Minterms for 3 variables (a, b, c).

A. 0
B. 2
C. 8
D. 1
Answer» C. 8
122.

                           expressions can be implemented using either (1) 2-level AND- OR logic circuits or (2) 2-level NAND logic circuits.

A. pos
B. literals
C. sop
D. pos
Answer» C. sop
123.

There are              cells in a 4-variable K- map.

A. 12
B. 16
C. 18
D. 8
Answer» B. 16
124.

The prime implicant which has at least one element that is not present in any other implicant is known as                        

A. essential prime implicant
B. implicant
C. complement
D. prime complement
Answer» A. essential prime implicant
125.

Product-of-Sums expressions can be implemented using                        

A. 2-level or-and logic circuits
B. 2-level nor logic circuits
C. 2-level xor logic circuits
D. both 2-level or-and and nor logic circuits
Answer» D. both 2-level or-and and nor logic circuits
126.

Each product term of a group, w’.x.y’ and w.y, represents the                         in that group.

A. input
B. pos
C. sum-of-minterms
D. sum of maxterms
Answer» C. sum-of-minterms
127.

It should be kept in mind that don’t care terms should be used along with the terms that are present in                        

A. minterms
B. expressions
C. k-map
D. latches
Answer» A. minterms
128.

Using the transformation method you can realize any POS realization of OR-AND with only.

A. xor
B. nand
C. and
D. nor
Answer» D. nor
129.

In case of XOR/XNOR simplification we have to look for the following

A. diagonal adjacencies
B. offset adjacencies
C. straight adjacencies
D. both diagonal and offset adjencies
Answer» D. both diagonal and offset adjencies
130.

In which of the following gates the output is 1 if and only if at least one input is 1?

A. and
B. nor
C. nand
D. or
Answer» D. or
131.

The time required for a gate or inverter to change its state is called                      

A. rise time
B. decay time
C. propagation time
D. charging time
Answer» C. propagation time
132.

Odd parity of word can be conveniently tested by                        

A. or gate
B. and gate
C. nand gate
D. xor gate
Answer» D. xor gate
133.

The number of full and half adders are required to add 16-bit number is                      

A. 8 half adders, 8 full adders
B. 1 half adders, 15 full adders
C. 16 half adders, 0 full adders
D. 4 half adders, 12 full adders
Answer» B. 1 half adders, 15 full adders
134.

An OR gate can be imagined as

A. switches connected in series
B. switches connected in parallel
C. mos transistor connected in series
D. bjt transistor connected in series
Answer» B. switches connected in parallel
135.

In parts of the processor, adders are used to calculate                          

A. addresses
B. table indices
C. increment and decrement operators
D. all of the mentioned
Answer» D. all of the mentioned
136.

How many full adders are required to construct an m-bit parallel adder?

A. m/2
B. m
C. m-1
D. m+1
Answer» C. m-1
137.

In which operation carry is obtained?

A. subtraction
B. addition
C. multiplication
D. both addition and subtraction
Answer» B. addition
138.

If A and B are the inputs of a half adder, the sum is given by                      

A. a and b
B. a or b
C. a xor b
D. a ex-nor b
Answer» C. a xor b
139.

If A and B are the inputs of a half adder, the carry is given by                      

A. a and b
B. a or b
C. a xor b
D. a ex-nor b
Answer» A. a and b
140.

Half-adders have a major limitation in that they cannot                      

A. accept a carry bit from a present stage
B. accept a carry bit from a next stage
C. accept a carry bit from a previous stage
D. accept a carry bit from the following stages
Answer» C. accept a carry bit from a previous stage
141.

The difference between half adder and full adder is                      

A. half adder has two inputs while full adder has four inputs
B. half adder has one output while full adder has two outputs
C. half adder has two inputs while full adder has three inputs
D. all of the mentioned
Answer» C. half adder has two inputs while full adder has three inputs
142.

If A, B and C are the inputs of a full adder then the sum is given by                      

A. a and b and c
B. a or b and c
C. a xor b xor c
D. a or b or c
Answer» C. a xor b xor c
143.

If A, B and C are the inputs of a full adder then the carry is given by                      

A. a and b or (a or b) and c
B. a or b or (a and b) c
C. (a and b) or (a and b)c
D. a xor b xor (a xor b) and c
Answer» A. a and b or (a or b) and c
144.

How many AND, OR and EXOR gates are required for the configuration of full

A. 1, 2, 2
B. 2, 1, 2
C. 3, 1, 2
D. 4, 0, 1
Answer» B. 2, 1, 2
145.

Half subtractor is used to perform subtraction of                        

A. 2 bits
B. 3 bits
C. 4 bits
D. 5 bits
Answer» A. 2 bits
146.

How many outputs are required for the implementation of a subtractor?

A. 1
B. 2
C. 3
D. 4
Answer» B. 2
147.

Let the input of a subtractor is A and B then what the output will be if A = B?

A. 0
B. 1
C. a
D. b
Answer» A. 0
148.

Let A and B is the input of a subtractor then the output will be                        

A. a xor b
B. a and b
C. a or b
D. a exnor b
Answer» A. a xor b
149.

Let A and B is the input of a subtractor then the borrow will be                        

A. a and b’
B. a’ and b
C. a or b
D. a and b
Answer» B. a’ and b
150.

What does minuend and subtrahend denotes in a subtractor?

A. their corresponding bits of input
B. its outputs
C. its inputs
D. borrow bits
Answer» C. its inputs

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