Editing Programming language (section)

===Specification===
{{Main|Programming language specification}}

The specification of a programming language is an artifact that the language [[programmer|users]] and the [[programming language implementation|implementors]] can use to agree upon whether a piece of [[source code]] is a valid [[computer program|program]] in that language, and if so what its behavior shall be.

A programming language specification can take several forms, including the following:
* An explicit definition of the syntax, static semantics, and execution semantics of the language. While syntax is commonly specified using a formal grammar, semantic definitions may be written in [[natural language]] (e.g., as in the [[C (programming language)|C language]]), or a [[formal semantics of programming languages|formal semantics]] (e.g., as in [[Standard ML]]<ref>{{cite book|last=Milner|first=R.|author-link=Robin Milner |author2=[[Mads Tofte|M. Tofte]] |author3=[[Robert Harper (computer scientist)|R. Harper]] |author4=D. MacQueen |title=The Definition of Standard ML (Revised)|publisher=MIT Press|year=1997|isbn=978-0-262-63181-5}}</ref> and [[Scheme (programming language)|Scheme]]<ref>{{cite web|first=Richard|last=Kelsey|author2=William Clinger|author3=Jonathan Rees|title=Section 7.2 Formal semantics|work=Revised<sup>5</sup> Report on the Algorithmic Language Scheme|url=http://www.schemers.org/Documents/Standards/R5RS/HTML/r5rs-Z-H-10.html#%_sec_7.2|date=February 1998|url-status=live|archive-url=https://web.archive.org/web/20060706081110/http://www.schemers.org/Documents/Standards/R5RS/HTML/r5rs-Z-H-10.html#%_sec_7.2|archive-date=6 July 2006}}</ref> specifications).
* A description of the behavior of a [[compiler|translator]] for the language (e.g., the [[C++]] and [[Fortran]] specifications). The syntax and semantics of the language have to be inferred from this description, which may be written in natural or formal language.
* A [[reference implementation|''reference'' or ''model'' implementation]], sometimes [[Meta-circular evaluator|written in the language being specified]] (e.g., [[Prolog]] or [[REXX|ANSI REXX]]<ref>[[American National Standards Institute|ANSI]] – Programming Language Rexx, X3-274.1996</ref>). The syntax and semantics of the language are explicit in the behavior of the reference implementation.