If (11X1Y)₈ = (12C9)₁₆, then the values of X and Y are
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Correct answer: (C) 3, 1
Explanation
(12C9)₁₆ = 1 0010 1100 1001₂. Regrouped in threes from the right this is 1 001 011 001 001 = (11311)₈, so X = 3 and Y = 1.
BPSC TRE · Topic-wise previous year questions
Computer Science Previous Year Questions (page 7)
313 Computer Science questions asked in BPSC TRE previous year papers, each with the correct answer and explanation. Read them free on UTpaper, or attempt the full papers as timed online tests.
- 313 questions
- 9 topics
- Official answer key
- Free
Practise by topic
Which of the following 4-bit numbers equals its 2’s complement?
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Correct answer: (C) 1000
Explanation
For 1000, inverting gives 0111 and adding 1 gives 1000, so it equals its own 2's complement. 1000 is −8, which has no positive counterpart in 4 bits.
The number of 1’s in the binary representation of the value of the decimal expression 16³ × 9 + 16² × 7 + 16 × 5 + 3 is
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Correct answer: (B) 9
Explanation
The expression is (9753)₁₆ = 1001 0111 0101 0011₂. The 1s per group are 2 + 3 + 2 + 2 = 9.
The Boolean expression x + x′y equals
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Correct answer: (A) x + y
Explanation
x + x′y = (x + x′)(x + y) = 1·(x + y) = x + y, using the distributive law.
The Boolean expression AB + AB′ + A′C + AC is independent of Boolean variable
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Correct answer: (B) B
Explanation
AB + AB′ = A(B + B′) = A, and A + A′C + AC = A + C. The result A + C does not contain B.
The Boolean expression A + BC equals
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Correct answer: (C) (A + B)(A + C)
Explanation
By the distributive law of Boolean algebra, A + BC = (A + B)(A + C).
The Boolean expression x + xy will be equal to
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Correct answer: (A) x
Explanation
By the absorption law, x + xy = x(1 + y) = x.
The Boolean expression x(x + y) is equal to
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Correct answer: (A) x
Explanation
By absorption, x(x + y) = x + xy = x.
If x is a Boolean variable, then (((x′)′)′)′ will be
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Correct answer: (B) x
Explanation
There are four complements in a row, an even number, so they cancel out and the result is x.
In two-valued Boolean algebra, the maximum number of Boolean functions for two variables will be
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Correct answer: (C) 16
Explanation
With n variables there are 2^(2ⁿ) Boolean functions. For n = 2 that is 2⁴ = 16.
Simplified Boolean function of Boolean function F = A′C + A′B + AB′C + BC is
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Correct answer: (A) F = C + A′B
Explanation
F covers minterms 1, 2, 3, 5 and 7. Minterms 1, 3, 5 and 7 group to C, and 2 and 3 group to A′B, so F = C + A′B.
Which of the following logic gates is called universal gate?
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Correct answer: (C) NAND
Explanation
NAND (like NOR) is a universal gate, because AND, OR and NOT can all be built from NAND gates alone.
The minimum number of NAND gates required to implement Boolean function f = x′y + xy′ is
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Correct answer: (B) 4
Explanation
x′y + xy′ is XOR, and XOR needs at least 4 NAND gates. One NAND makes (xy)′, two NANDs combine it with x and with y, and a fourth NAND joins their outputs.
How to use these BPSC TRE Computer Science questions
Every question here was asked in a real BPSC TRE paper; the paper and shift are shown on the card, and the number opens the question on its own page. Try each one before tapping Show answer, then attempt the full BPSC TRE papers as timed tests to check your speed under exam conditions.