Computer Architecture Q&A (PDF), Exams of
Architecture
Section 1: Digital Logic & Number Systems (Questions 1–25)
1. Convert the binary number 11011010₂ to decimal.
A) 210
B) 218
C) 202
D) 194
Answer: B) 218
Rationale: 11011010₂ = 1×2⁷ + 1×2⁶ + 0×2⁵ + 1×2⁴ + 1×2³ + 0×2² + 1×2¹ + 0×2⁰ =
128 + 64 + 0 + 16 + 8 + 0 + 2 + 0 = 218.
2. Convert the decimal number 157 to hexadecimal.
A) 9D₁₆
B) 9E₁₆
C) 8D₁₆
D) A9₁₆
,Answer: A) 9D₁₆
Rationale: 157 ÷ 16 = 9 remainder 13 (D). So 157₁₀ = 9D₁₆.
3. Which of the following is the two's complement representation of -35 in 8
bits?
A) 11011101₂
B) 00100011₂
C) 11011100₂
D) 00100100₂
Answer: A) 11011101₂
Rationale: 35 in binary = 00100011₂. Invert: 11011100₂. Add 1: 11011101₂.
4. The Boolean expression for a NAND gate is:
A) F = A · B
B) F = A + B
C) F = (A · B)'
D) F = (A + B)'
Answer: C) F = (A · B)'
,Rationale: NAND (NOT AND) outputs the inverse of the AND
operation.
5. Which logic gate is equivalent to a NOT gate followed by an AND gate?
A) NAND
B) NOR
C) XOR
D) XNOR
Answer: A) NAND
Rationale: NAND = NOT (AND). A NAND gate is equivalent to an AND
gate with an inverted output.
6. Simplify the Boolean expression: F = A·B + A·B' + A'·B
A) A + B
B) A·B
C) A ⊕ B
D) A + B'
Answer: A) A + B
, Rationale: A·B + A·B' = A(B + B') = A. Then A + A'·B = A + B.
7. A 4-to-1 multiplexer has how many select lines?
A) 1
B) 2
C) 3
D) 4
Answer: B) 2
Rationale: A multiplexer with 2ⁿ inputs requires n select lines. For 4
inputs, n = 2.
8. Which of the following is a characteristic of a D flip-flop?
A) Output toggles on each clock edge
B) Output follows the input when clock is high
C) Output is set to the input value on the clock edge
D) Output is the complement of the input
Answer: C) Output is set to the input value on the clock edge