Quine (computing)

Quine (computing)

A quine is a computer program which takes no input and produces a copy of its own source code as its only output. The standard terms for these programs in the computability theory and computer science literature are self-replicating programs, self-reproducing programs, and self-copying programs.

A quine is a fixed point of an execution environment, when the execution environment is viewed as a function. Quines are possible in any programming language that has the ability to output any computable string, as a direct consequence of Kleene's recursion theorem. For amusement, programmers sometimes attempt to develop the shortest possible quine in any given programming language.

In some languages, an empty source file is a fixed point of the language, producing no output. Such an empty program, submitted as "the world's smallest self reproducing program", once won the "worst abuse of the rules" prize in the International Obfuscated C Code Contest.