Question

what is mean by encoder and decoder?

Answer 1

ENCODER = Encoder is one who encrypts the program..

DECODER = Decoder is one who decrypts the program.

Answer 2

An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed or compression.

A decoder is simppy the opposite of it i.e. it does the opposite work of an encoder.

in simple language an encoder converts a text or a message into different language than it is actually written in so as to hide from other people or for easy transmission or for the compression of data.
a decoder is required to turn the encoded data into the actual message.