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Question 2Asked in UGC NET Computer Science, June 2015 (Paper II & III, Selected Questions)

Consider a full-adder with the following input values : (a) x = 1, y = 0 and C₁ (carry input) = 0

Consider a full-adder with the following input values : (a) x = 1, y = 0 and C₁ (carry input) = 0 (b) x = 0, y = 1 and C₁ = 1 Compute the values of S (sum) and C₀ (carry output) for the above input values.
  1. AS = 1, C₀ = 0 and S = 0, C₀ = 1
  2. BS = 0, C₀ = 0 and S = 1, C₀ = 1
  3. CS = 1, C₀ = 1 and S = 0, C₀ = 1
  4. DS = 0, C₀ = 1 and S = 1, C₀ = 0
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Correct answer: (A) S = 1, C₀ = 0 and S = 0, C₀ = 1

Explanation

For a full adder, S = A ⊕ B ⊕ Cᵢₙ and Cₒᵤₜ = A·B + Cᵢₙ·(A ⊕ B). (a) A = 1, B = 0, Cᵢₙ = 0: S = 1 ⊕ 0 ⊕ 0 = 1, Cₒᵤₜ = 1·0 + 0·(1 ⊕ 0) = 0. (b) A = 0, B = 1, Cᵢₙ = 1: S = 0 ⊕ 1 ⊕ 1 = 0, Cₒᵤₜ = 0·1 + 1·(0 ⊕ 1) = 1. So S = 1, C₀ = 0 and S = 0, C₀ = 1.

From UGC NET Computer Science PYQ, June 2015 (Paper II & III, Selected Questions)

This is question 2 of UGC NET Computer Science PYQ, June 2015 (Paper II & III, Selected Questions). See all questions of this paper with answers, or attempt the paper as a timed online test to get your score and all-India rank.