In this section we deal with 'logic gates'.We use xi to represent the value of the input(s) to a gate and the variable z to represent its output.A logic gate is an electronic component, incorporated within a circuit, which operates on one or more inputs to produce one output.These are electronic devices which may be viewed as the basic functional components of a digital computer.Because of the 'two-value' nature of the input and output variables, a logic gate is an example of a binary device.