A directory of Objective Type Questions covering all the Computer Science subjects. Here you can access and discuss Multiple choice questions and answers for various compitative exams and interviews.

1. Which one of the following expressions does NOT represent exclusive NOR of x and y?
a. xy + x' y'
b. x ^ y' where ^ is XOR
c. x' ^ y where ^ is XOR
d. x' ^ y' where ^ is XOR
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Answer: (d).x' ^ y' where ^ is XOR

2. The simplified SOP (Sum Of Product) form of the boolean expression (P + Q' + R') . (P + Q' + R) . (P + Q + R') is
a. (P'.Q + R')
b. (P + Q'.R')
c. (P'.Q + R)
d. (P.Q + R)
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Answer: (b).(P + Q'.R')

3. The minterm expansion of f(P, Q, R) = PQ + QR' + PR' is
a. m2 + m4 + m6 + m7
b. m0 + m1 + m3 + m5
c. m0 + m1 + m6 + m7
d. m2 + m3 + m4 + m5
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Answer: (a).m2 + m4 + m6 + m7

4. What is the minimum number of gates required to implement the Boolean function (AB+C)if we have to use only 2-input NOR gates?
a. 2
b. 3
c. 4
d. 5
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Answer: (b).3

5. If P, Q, R are Boolean variables, then (P + Q')(PQ' + PR)(P'R' + Q') simplifies
a. PQ'
b. PR'
c. PQ' + R
d. PR'' + Q
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Answer: (a).PQ'

6. How many 3-to-8 line decoders with an enable input are needed to construct a 6-to-64 line decoder without using any other logic gates?
a. 7
b. 8
c. 9
d. 10
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Answer: (c).9

7. Consider the following Boolean function of four variables: f(w,x,y,z) = ∑(1,3,4,6,9,11,12,14) The function is:
a. independent of one variables
b. independent of two variables
c. independent of three variables
d. dependent on all the variables
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Answer: (b).independent of two variables

8. Let f(w, x, y, z) = ∑(0, 4, 5, 7, 8, 9, 13, 15). Which of the following expressions are NOT equivalent to f?
a. x'y'z' + w'xy' + wy'z + xz
b. w'y'z' + wx'y' + xz
c. w'y'z' + wx'y' + xyz + xy'z
d. x'y'z' + wx'y' + w'y
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Answer: (d).x'y'z' + wx'y' + w'y

9. Define the connective * for the Boolean variables X and Y as: X * Y = XY + X' Y'. Let Z = X * Y.
Consider the following expressions P, Q and R.

P: X = Y⋆Z
Q: Y = X⋆Z
R: X⋆Y⋆Z=1

Which of the following is TRUE?
a. Only P and Q are valid
b. Only Q and R are valid
c. Only P and R are valid
d. All P, Q, R are valid
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Answer: (d).All P, Q, R are valid

10. Suppose only one multiplexer and one inverter are allowed to be used to implement any Boolean function of n variables. What is the minimum size of the multiplexer needed?
a. 2^n line to 1 line
b. 2^(n+1) line to 1 line
c. 2^(n-1) line to 1 line
d. 2^(n-2) line to 1 line
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Answer: (c).2^(n-1) line to 1 line

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