In a combinational circuit, the output depends upon present input(s) only i.e, not dependant on the previous input(s). The combinational circuit has no memory element. It consists of logic gates only.
The two characteristics of combinational circuits are:
In combinational circuits, the output exists as long as the input exists.
A combinational circuit will always respond in the same fashion to the input function, when we apply signal to the input terminal of the combinational logic circuit.