Which description correctly identifies an AND gate?

• A. Outputs a sum of inputs
• B. Inverts the input
• C. Outputs true when any input is true
• D. Outputs true only when both inputs are true

Answer: (D)

An AND gate performs the logical AND operation: its output is true only if every input is true. In digital terms, true is typically represented as 1 (high voltage) and false as 0 (low voltage). If both inputs are 1, the gate outputs 1; if either input is 0, the output is 0. With more than two inputs, the output is 1 only if all inputs are 1. The idea that a gate outputs a sum of inputs isn’t correct for a single logic gate, since that would imply arithmetic addition. The notion of inverting the input describes a NOT gate. The idea of outputting true when any input is true describes an OR gate. The description that matches an AND gate is the one that outputs true only when both inputs are true.