A logic gate is an elementary building block of a digital circuit .
Most logic gates have two inputs and one output.
The logic state of a terminal can, and generally does, change often, as the circuit processes data. The following illustration and table show the circuit symbol and logic combinations for an AND gate. Another way of looking at this circuit is to observe that the output is 1 if the inputs are different, but 0 if the inputs are the same. A logical inverter , sometimes called a NOT gate to differentiate it from other types of electronic inverter devices, has only one input. It reverses the logic state.