Question

An AND Gate has 7 inputs. How many input words are in its truth table?

• A. 7
• B. 14
• C. 128
• D. 256

Hint:

Number of input words equals 2 raised to the number of inputs.

Answer 1

The Correct Option is C

Each input line is a single bit that can be low or high. Seven such lines together form a 7-bit input word.

The number of different 7-bit words equals the number of ways to fill 7 slots with two choices each:
\[2 \times 2 \times 2 \times 2 \times 2 \times 2 \times 2 = 2^{7}\]

That total is 128, so the truth table needs 128 input rows regardless of the gate type.

\[\boxed{128 \text{ (C)}}\]