1. Encoder- This is a combinational circuit that perform the reverse operation of Decoder. It has maximum of 2n inputs line and n output lines. It will produce a binary code equivalent to the input which is active high. Therefore ,the encoder encodes 2n input lines with ‘n’ bits. It is optional to represent the enable signal in encoders.

2. Decoder- This is a combinational circuit that has ‘n’ input lines and maximum of 2n output lines. One of these outputs will be active High based on the combination of inputs present, when the decoder is enabled. That means decoder detects a particular code.