Q 12-14-167JEE MainJEE Main 2020 (7 Jan, Shift 1)Medium
Which of the following gives a reversible operation?
Answer: (D) see figure
An operation is reversible if the input can be recovered uniquely from the output.
A two-input gate (OR, NOR, NAND) gives the same output for several different input combinations (for example, OR gives 1 for 01, 10 and 11), so the inputs cannot be recovered.
A NOR gate with both inputs joined acts as a NOT gate: $Y = \overline{A + A} = \bar A$. Each output corresponds to exactly one input, so this operation is reversible.
Solution by Sreeraj P, M.Sc Physics