Definition of decoder

The term "decoder" originated during the World War II era as avalanche­like numbers of encrypted messages flooded military communications. It refers to a device or a process that dec­iphers or interprets encoded messages into plain text or intelligible signals. The prefix "de-" denotes reversal or removal of an operation, implying that a decoder performs the opposite of an encoder, which is used to transform plain text into cryptographic codes. Encryption and decryption techniques were called cipher or cryptography during the early days because of the use of complex symbols or substitution ciphers that required a cipher key. The emergence of IBM Corporation's binary arithmetic-based machines in the 1940s spawned new computational means to automate encoding and decoding, notably electronic computers and programmable logic devices such as field-programmable gate arrays (FPGAs). Nowadays, decoders exist not only in secure communications but also in everyday technologies like digital television, DVD players, and modern wireless communication systems such as cell phones and satellite networks that utilize complex decoding algorithms to recover encoded video, audio, and signals from compression, multiplexing, and error correction processes.