Editing Metasyntactic variable (section)

{{Short description|Placeholder term used in computer science}}
{{About|metasyntactic variables in computer science and programming|metasyntactic variables as used in formal logic|Metavariable (logic)|usage in spoken languages|Placeholder name}}
A '''metasyntactic variable''' is a specific word or set of words identified as a [[placeholder name|placeholder]] in [[computer science]] and specifically [[computer programming]]. These words are commonly found in [[source code]] and are intended to be modified or substituted before real-world usage. For example, [[Foobar|''foo'' and ''bar'']] are used in over 330 [[Internet Engineering Task Force]] [[Request for Comments|Requests for Comments]], the documents which define foundational internet technologies like [[HTTP]] (web), [[TCP/IP]], and [[email]] [[Communications protocol|protocol]]s.<ref name="RFC3092">{{cite IETF|rfc=3092|title=Etymology of "Foo"|first1=Donald E.|last1=((Eastlake 3rd))|first2=Carl-Uno|last2=Manros|first3=Eric S.|last3=Raymond}}</ref><ref>{{Cite web|url=https://www.rfc-editor.org/retrieve/|title=Document Retrieval|work=RFC Editor}}</ref>

By mathematical [[analogy]], a [[metasyntax|metasyntactic]] variable is a word that is a [[Variable (mathematics)|variable]] for other words, just as in [[algebra]] letters are used as variables for [[number]]s.<ref name="RFC3092"/>{{Failed verification|date=March 2025|reason=Source does not mention "math" or "algebra", nor "analogy" or "number" in a relevant context. If the source uses other terms to discuss this topic, please add a quote to this citation.}}

Metasyntactic variables are used to name entities such as variables, [[Function (computer programming)|function]]s, and [[Command (programming)|command]]s whose exact identity is unimportant and serve only to demonstrate a concept, which is useful for teaching programming.