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"- wikipedia 
A quine's output is exactly the same as its source code. (Note that the syntax highlighting demonstrated by the text editor in the upper half of the image does not affect the output of the.. - wikimedia
A quine is a Fixed point (mathematics) of an execution environment, when the execution environment is viewed as a Function (mathematics) transforming programs into their outputs. Quines are possible in any Turing completeness programming language, 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.
The name "quine" was coined by Douglas Hofstadter, in his popular science book ''Gödel, Escher, Bach'', in honor of philosopher Willard Van Orman Quine (1908–2000), who made an extensive study of indirect self-reference, and in particular for the following paradox-producing expression, known as Quine's paradox:
"Yields falsehood when preceded by its quotation" yields falsehood when preceded by its quotation.
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