Prefix code: Difference between revisions

Revision as of 04:48, 28 September 2024

Latest revision as of 12:06, 12 May 2025

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{{Short description|Type of code system}}

A '''prefix code''' is a type of [[code]] system distinguished by its possession of the "'''prefix property"''', which requires that there is no whole [[Code word (communication)|code word]] in the system that is a [[prefix (computer science)|prefix]] (initial segment) of any other code word in the system. It is trivially true for fixed-length codes, so only a point of consideration for [[variable-length code|variable-length codes]].

For example, a code with code {9, 55} has the prefix property; a code consisting of {9, 5, 59, 55} does not, because "5" is a prefix of "59" and also of "55". A prefix code is a [[uniquely decodable code]]: given a complete and accurate sequence, a receiver can identify each word without requiring a special marker between words. However, there are uniquely decodable codes that are not prefix codes; for instance, the reverse of a prefix code is still uniquely decodable (it is a suffix code), but it is not necessarily a prefix code.