GATE EE 2007 Digital Electronics Q 1 - Grad Plus
GATE EE 2007 Digital Electronics Q 1

GATE EE 2007 Digital Electronics Q 1

A, B, C, and D are input, and Y is the output bit in the XOR gate circuit of the figure below. Which of the following statements about the sum S of A, B, C, D and Y is correct?

a) S is always either zero or odd.

b) S is always either zero or even.

c) S=1 only if the sum of A, B, C and D is even.

d) S=1 only if the sum of A, B, C and D is odd.

Ans: (b)

Explanation

From the given diagram, we have

Y=A\oplus B\oplus C\oplus D

Now, sum of any no. of bits is given as,

S=A\oplus B\oplus C\oplus D\oplus Y S=Y\oplus Y=0
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