Logic circuit for Digital system may be combinational or sequential. A combinational circuit consists of Logic Gates whose output at any time are determined from the present combination of input. A Boolean circuit perform an operation that can be specified logically by a set of Boolean function.
Each input and out variable exists physically as a binary signal that represent logic “1” and Logic “0”. In many application the source and destination are store registers.
It the register are include with the combinational Gates, then the total circuit considered as sequential circuit. There are several combinational circuit that are employed extensively in the design of digital system.
There are some important standard combinational circuit for Example Multiplexer, De-multiplexer, Decoder, Encoder, Parity Checker, party Generator, Magnitude Comparator etc.
These component are available in interpreted as MSI (medium scale integration) circuit. They are also used as standard cells in complex VLSI circuit.