Bits, Signals & Truth Tables

In the binary logic model used here, a signal has two values: 1 (high / on / true) and 0 (low / off / false). One such value is a bit. Real circuits represent these with voltage ranges and take time to switch between them.

A logic gate takes one or more input bits and produces an output bit by a fixed rule. Because the inputs are finite, we can list every possible case in a truth table — there is no guesswork in digital logic.