The GATE Grind

GATE 2014 CS (CS3) – Question 18

Digital Logic · Combinational Circuits · 1 mark · Multiple choice

A combinational block has Boolean inputs x,a,b and output y:

f(x,y,a,b) {
if (x is 1) y = a;
else y = b;
}

Which digital block is most suitable?

  1. Full adder
  2. Priority encoder
  3. Multiplexor
  4. Flip-flop

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Show answer and explanation

Correct answer: (C) Multiplexor

Explanation

The function selects a when x=1and b when x=0, so y=xa+x̄b. This is precisely a2-to-1 **multiplexer,C**, with xasselect. A flip-flop would introduce state, which the combinational specification does not require.