A technician is testing an unlabelled two-input logic gate taken from a circuit board. She sets every possible combination of inputs A and B and records the output each time. A B Output 0 0 1 0 1 0 1 0 0 1 1 0 Which single logic gate produces this truth table?

Answer: C. Step 1: Recall the rule for each candidate gate - AND outputs 1 only when both inputs are 1. - OR outputs 1 whenever at least one input is 1. - XOR outputs 1 only when the two inputs are different. - NOR outputs 1 only when both inputs are…

IGCSE Computer Science 0478: Identifying a Logic Gate from Its Truth Table

A	B	Output
0	0	1
0	1	0
1	0	0
1	1	0

Output

Step 1: Recall the rule for each candidate gate

AND outputs 1 only when both inputs are 1.
OR outputs 1 whenever at least one input is 1.
XOR outputs 1 only when the two inputs are different.
NOR outputs 1 only when both inputs are 0, and 0 in every other case.

Step 2: Test each rule against the recorded table

Row by row, the technician recorded: (0,0) → 1, (0,1) → 0, (1,0) → 0, (1,1) → 0.

Testing AND: it would require (1,1) → 1, but the table shows 0. AND is ruled out.
Testing OR: it would require (0,1), (1,0) and (1,1) all → 1, but the table shows 0 in each of those rows. OR is ruled out.
Testing XOR: it would require (0,1) and (1,0) → 1, but the table shows 0 in both. XOR is ruled out.
Testing NOR: it requires 1 only for (0,0) and 0 everywhere else, this matches the table exactly.

Step 3: Confirm the match

Only the NOR rule reproduces every row of the recorded truth table, so the unlabelled gate must be a NOR gate.

Final answer

The gate is NOR, option C.