## Quick Reference

**source alphabet**) into another (the **target alphabet**), usually without loss of information. The process of transformation is called encoding and its converse is called decoding. These processes are carried out by an encoder and a decoder respectively; the encoder and decoder may be implemented in hardware or software, the encoding and decoding processes being algorithmic in nature. The term “an encoding” is sometimes used synonymously with “a code”. From a more formal viewpoint, a code is a one-to-one homomorphism *h* from the set of Σ-words, Σ_{1}*, to the set Σ_{2}*, where Σ_{1} and Σ_{2} are alphabets (see word, formal language). Since *h* is one to one, *h*(*w*) may be “decoded” to obtain *w* for any *w* in Σ_{1}*.

See also fixed-length code, variable-length code, error-correcting code, error-detecting code, channel coding theorem, source coding theorem, cryptography.

**From:**
code
in
A Dictionary of Computing »

*Subjects:*
Computing.