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{{Short description|Set of rules for naming entities in source code and documentation
{{Use dmy dates|date=October 2020}}
In [[computer programming]], a '''naming convention''' is a set of rules for choosing the character sequence to be used for [[identifier (computer languages)|identifier]]s which denote [[Variable (computer science)|variables]], [[Data type|types]], [[Subroutine|functions]], and other entities in [[source code]] and [[Software documentation|documentation]].
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One approach is to [[delimiter|delimit]] separate words with a [[alphanumeric|non-alphanumeric]] character. The two characters commonly used for this purpose are the [[hyphen]] ("-") and the [[underscore]] ("_"); e.g., the two-word name "<code>two words</code>" would be represented as "<code>two-words</code>" or "<code>two_words</code>".
The hyphen is used by nearly all programmers writing [[COBOL]] (1959), [[Forth (programming language)|Forth]] (1970), and [[Lisp (programming language)|Lisp]] (1958); it is also common in [[Unix]] for commands and packages, and is used in [[Cascading Style Sheets|CSS]].<ref>{{cite web |title = CSS reference |website = [[Mozilla Developer Network]] |url = https://developer.mozilla.org/en-US/docs/Web/CSS/Reference |access-date=2016-06-18}}</ref> This convention has no standard name, though it may be referred to as ''lisp-case'' or ''COBOL-CASE'' (compare ''Pascal case''), ''kebab-case'', ''brochette-case'', or other variants.<ref>{{Cite web | title = StackOverflow – What's the name for snake_case with dashes? | url = https://stackoverflow.com/questions/11273282/whats-the-name-for-snake-case-with-dashes }}</ref><ref>{{Cite web | title = Programmers – If this is camelCase what-is-this? | url = http://programmers.stackexchange.com/questions/104468/if-this-is-camelcase-what-is-this | access-date = 13 August 2015 | archive-date = 7 August 2016 | archive-url = https://web.archive.org/web/20160807114459/http://programmers.stackexchange.com/questions/104468/if-this-is-camelcase-what-is-this | url-status = dead }}</ref><ref>{{Cite web | title = Camel_SNAKE-kebab | website = [[GitHub]] | url = https://github.com/qerub/camel-snake-kebab | date = September 2019 }}</ref><ref>[http://c2.com/cgi/wiki?UnderscoreVersusCapitalAndLowerCaseVariableNaming UnderscoreVersusCapitalAndLowerCaseVariableNaming]</ref> Of these, ''kebab-case'', dating at least to 2012,<ref>{{cite web |url=https://stackoverflow.com/posts/12273101/revisions |title=Revisions to jwfearn's answer to What's the name for dash-separated case? |date=5 September 2012 |author=jwfearn}}</ref> has achieved some currency since.<ref>''Living Clojure'' (2015), by Carin Meier, [https://books.google.com/books?id=b4odCAAAQBAJ&pg=PA91 p. 91]</ref><ref>[https://lodash.com/docs#kebabCase lodash: kebabCase]</ref>
By contrast, languages in the FORTRAN/ALGOL tradition, notably languages in the [[C (programming language)|C]] and [[Pascal (programming language)|Pascal]] families, used the hyphen for the [[subtraction]] [[infix notation|infix]] operator, and did not wish to require spaces around it (as [[free-form language]]s), preventing its use in identifiers.
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==Language-specific conventions==
===ActionScript===
Adobe's Coding Conventions and Best Practices suggests naming standards for [[ActionScript]] that are mostly consistent with those of [[ECMAScript]].<ref>{{
===Ada===
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===C and C++===
In [[C (programming language)|C]] and [[C++]], [[keyword (computer programming)|keyword]]s and [[standard library]] identifiers are mostly lowercase. In the [[C standard library]], abbreviated names are the most common (e.g. <code>isalnum</code> for a function testing whether a character is alphanumeric), while the [[C++ standard library]] often uses an underscore as a word separator (e.g. <code>out_of_range</code>). Identifiers representing [[C preprocessor#Macro definition and expansion|macros]] are, by convention, written using only uppercase letters and underscores, for example <code>NULL</code> and <code>EINVAL</code> (this is related to the convention in many programming languages of using all-upper-case identifiers for constants). Names containing double underscore or beginning with an underscore and a capital letter are reserved for implementation ([[compiler]], [[standard library]]) and should not be used (e.g. <code>__reserved</code> or <code>_Reserved</code>).<ref>{{Cite web | title = ISO/IEC 9899:1999 Programming languages – C | publisher = ISO | url = http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=29237}}</ref><ref>{{Cite web | title = ISO/IEC 14882:2011 Information technology – Programming languages – C++ | publisher = ISO | url = http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50372}}</ref> This is superficially similar to [[Stropping (syntax)|stropping]], but the semantics differ: the underscores are part of the value of the identifier, rather than being quoting characters (as is stropping): the value of <code>__foo</code> is <code>__foo</code> (which is reserved), not <code>foo</code> (but in a different namespace).
===C#===
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===Pascal, Modula-2 and Oberon===
Wirthian languages Pascal, Modula-2 and Oberon generally use <code>Capitalized</code> or <code>UpperCamelCase</code> identifiers for programs, modules, constants, types and procedures, and <code>lowercase</code> or <code>lowerCamelCase</code> identifiers for math constants, variables, formal parameters and functions.<ref>[https://web.archive.org/web/20161008155209/http://modula-2.info/m2r10/pmwiki.php/Recommendations/NameConvention#Identifiers Modula-2 Name Convention]</ref> While some dialects support underscore and dollar signs in identifiers, snake case and macro case is more likely confined to use within foreign API interfaces.<ref>
===Perl===
[[Perl]] takes some cues from its C heritage for conventions. Locally scoped variables and subroutine names are lowercase with infix underscores. Subroutines and variables meant to be treated as private are prefixed with an underscore. Package variables are title cased. Declared constants are all caps. Package names are camel case excepting pragmata—e.g., <code>strict</code> and <code>
<ref>{{Cite web | title = Perl style guide | url = http://perldoc.perl.org/perlstyle.html }}</ref>
<ref>{{Cite web | title = perlmodlib – constructing new Perl modules and finding existing ones | url = http://perldoc.perl.org/perlmodlib.html }}</ref>
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=== R ===
While there is no official style guide for [[R (programming language)|R]], the [[tidyverse]] style guide from R-guru Hadley Wickham sets the standard for most users.<ref name=tidyverse>[https://style.tidyverse.org/ Style Guide for RCode ]</ref> This guide recommends
Its predecessors S and S-PLUS did not allow underscores in variable and function names, but instead used the period as a delimiter. As a result, many base functions in R still have a period as delimiter e.g. as.data.frame().
Hidden objects can be created with the dot prefix e.g. .hidden_object. These objects do not appear in the global environment. The dot prefix is often used by package developers for functions that are purely internal and are not supposed to be used by end users. It is similar to the underscore prefix in Python.
===Raku===
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