A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
A naming convention is a convention for naming things. The intent is to allow useful information to be deduced from the names based on regularities. For instance, in Manhattan, streets are numbered, with East-West streets being called "Streets" and North-South streets called "Avenues".-Use...
is a set of rules for choosing the character sequence to be used for identifier
Identifier
An identifier is a name that identifies either a unique object or a unique class of objects, where the "object" or class may be an idea, physical [countable] object , or physical [noncountable] substance...
s which denote variables, types and functions etc. in source code
Source code
In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...
and documentation.
Reasons for using a naming convention (as opposed to allowing programmer
Programmer
A programmer, computer programmer or coder is someone who writes computer software. The term computer programmer can refer to a specialist in one area of computer programming or to a generalist who writes code for many kinds of software. One who practices or professes a formal approach to...
s to choose any character sequence) include the following:
to reduce the effort needed to read and understand source code;
to enhance source code appearance (for example, by disallowing overly long names or unclear abbreviations).
The choice of naming conventions can be an enormously controversial issue, with partisans of each holding theirs to be the best and others to be inferior. Colloquially, this is said to be a matter of "religion". Many companies have also established their own set of conventions to best meet their interests.
Potential benefits
Some of the potential benefits that can be obtained by adopting a naming convention include the following:
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
) about the use to which an identifier is put;
to help formalize expectations and promote consistency within a development team;
Code refactoring is "disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior", undertaken in order to improve some of the nonfunctional attributes of the software....
or search and replace tools with minimal potential for error;
to enhance clarity in cases of potential ambiguity;
to enhance the aesthetic and professional appearance of work product (for example, by disallowing overly long names, comical or "cute" names, or abbreviations);
to help avoid "naming collisions" that might occur when the work product of different organizations is combined (see also: namespaces
Namespace (computer science)
A namespace is an abstract container or environment created to hold a logical grouping of unique identifiers or symbols . An identifier defined in a namespace is associated only with that namespace. The same identifier can be independently defined in multiple namespaces...
);
to provide meaningful data to be used in project handovers which require submission of program source code and all relevant documentation and
to provide better understanding in case of code reuse after a long interval of time.
Challenges
The choice of naming conventions (and the extent to which they are enforced) is often a contentious issue, with partisans holding their viewpoint to be the best and others to be inferior.
Moreover, even with known and well-defined naming conventions in place, some organizations may fail to consistently adhere to them, causing inconsistency and confusion.
These challenges may be exacerbated if the naming convention rules are internally inconsistent, arbitrary, difficult to remember, or otherwise perceived as more burdensome than beneficial.
Business value
Although largely hidden from the view of most business users, well-chosen identifiers make it significantly easier for subsequent generations of analysts and developers to understand what the system is doing and how to fix or extend the source code
Source code
In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...
for new business needs.
For example, although the following:
a = b * c;
is syntactically correct, it is entirely opaque as to intent or meaning. Contrast this with:
weekly_pay = hours_worked * pay_rate;
which implies the intent and meaning of the source code, at least to those familiar with the underlying context of the application.
Common elements
The exact rules of a naming convention depend on the context in which they are employed. Nevertheless, there are several common elements that influence most if not all naming conventions in common use today.
Length of identifiers
A fundamental element of all naming conventions are the rules related to identifier length (i.e., the finite number of individual characters allowed in an identifier). Some rules dictate a fixed numerical bound, while others specify less precise heuristics or guidelines.
Identifier length rules are routinely contested in practice, and subject to much debate academically.
Some considerations:
shorter identifiers may be preferred as more expedient, because they are easier to type
extremely short identifiers (such as 'i' or 'j') are very difficult to uniquely distinguish using automated search and replace tools
longer identifiers may be preferred because short identifiers cannot encode enough information or appear too cryptic
longer identifiers may be disfavored because of visual clutter
It is an open research issue whether some programmers prefer shorter identifiers because they are easier to type, or think up, than longer identifiers, or because in many situations a longer identifier simply clutters the visible code and provides no perceived additional benefit.
Brevity in programming could be in part attributed to:
early linkers which required variable names to be restricted to 6 characters to save memory. A later "advance" allowed longer variable names to be used for human comprehensibility, but where only the first few characters were significant. In some versions of BASIC
BASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
long names were allowed, but only the first two letters were significant; this led to terrible issues when variable names such as "VALUE" and "VAT" were used and intended to be distinct.
A source code editor is a text editor program designed specifically for editing source code of computer programs by programmers. It may be a standalone application or it may be built into an integrated development environment ....
Autocomplete is a feature provided by many web browsers, e-mail programs, search engine interfaces, source code editors, database query tools, word processors, and command line interpreters. Autocomplete involves the program predicting a word or phrase that the user wants to type in without the...
early low-resolution monitors with limited line length (e.g. only 80 characters)
much of computer science originating from mathematics, where variable names are often only a single letter
Letter case and numerals
Some naming conventions limit whether letters may appear in uppercase or lowercase. Other
conventions do not restrict letter case, but attach a well-defined interpretation based
on letter case. Some naming conventions specify whether alphabetic, numeric, or alphanumeric
characters may be used, and if so, in what sequence.
Multiple-word identifiers
A common recommendation is "Use meaningful identifiers." A single word
Word
In language, a word is the smallest free form that may be uttered in isolation with semantic or pragmatic content . This contrasts with a morpheme, which is the smallest unit of meaning but will not necessarily stand on its own...
may not be as meaningful, or specific, as multiple words. Consequently, some naming conventions specify rules for the treatment of "compound" identifiers containing more than one word.
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
In computer science, whitespace is any single character or series of characters that represents horizontal or vertical space in typography. When rendered, a whitespace character does not correspond to a visual mark, but typically does occupy an area on a page...
in identifiers, a method of delimiting each word is needed (to make it easier for subsequent readers to interpret which characters belong to which word).
Delimiter-separated words:
One approach is to delimit
Delimiter
A delimiter is a sequence of one or more characters used to specify the boundary between separate, independent regions in plain text or other data streams. An example of a delimiter is the comma character, which acts as a field delimiter in a sequence of comma-separated values.Delimiters represent...
Alphanumeric is a combination of alphabetic and numeric characters, and is used to describe the collection of Latin letters and Arabic digits or a text constructed from this collection. There are either 36 or 62 alphanumeric characters. The alphanumeric character set consists of the numbers 0 to...
character. The two characters commonly used for this purpose are the hyphen ('-') and the underscore ('_'), (e.g., the two-word name "two words" would be represented as "two-words" or "two_words"). The hyphen is used by nearly all programmers writing COBOL
COBOL
COBOL is one of the oldest programming languages. Its name is an acronym for COmmon Business-Oriented Language, defining its primary domain in business, finance, and administrative systems for companies and governments....
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
Pascal is an influential imperative and procedural programming language, designed in 1968/9 and published in 1970 by Niklaus Wirth as a small and efficient language intended to encourage good programming practices using structured programming and data structuring.A derivative known as Object Pascal...
families) reserve the hyphen for use as the subtraction
Subtraction
In arithmetic, subtraction is one of the four basic binary operations; it is the inverse of addition, meaning that if we start with any number and add any number and then subtract the same number we added, we return to the number we started with...
Infix notation is the common arithmetic and logical formula notation, in which operators are written infix-style between the operands they act on . It is not as simple to parse by computers as prefix notation or postfix notation Infix notation is the common arithmetic and logical formula notation,...
operator, so it is not available for use in identifiers and underscores are therefore used instead.
Letter-case separated words:
Another approach is to indicate word boundaries using medial capitalization
CamelCase
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
" and many other names), thus rendering "two words" as either "twoWords" or "TwoWords". This convention is commonly used in Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
Visual Basic is the third-generation event-driven programming language and integrated development environment from Microsoft for its COM programming model...
.
Metadata and hybrid conventions
Some naming conventions represent rules or requirements that go beyond the requirements
of a specific project or problem domain, and instead reflect a greater
over-arching set of principles defined by the software architecture
Software architecture
The software architecture of a system is the set of structures needed to reason about the system, which comprise software elements, relations among them, and properties of both...
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
Hungarian notation is an identifier naming convention in computer programming, in which the name of a variable or function indicates its type or intended use...
, which encodes either the purpose ("Apps Hungarian") or the type ("Systems Hungarian") of a variable in its name.
Positional Notation
A style used for very short (8 characters and less) could be: LCCIIL01, where LC would be the application (Letters of Credit), C for COBOL, IIL for the particular process subset, and the 01 a sequence number.
This sort of convention is still in active use in mainframes dependent upon JCL
Job Control Language
Job Control Language is a scripting language used on IBM mainframe operating systems to instruct the system on how to run a batch job or start a subsystem....
and is also seen in the 8.3 (maximum 8 characters with period separator followed by 3 character file type) MS-DOS style.
Composite word scheme (OF Language)
One of the earliest published convention systems was IBM's "OF Language" documented in a 1980s IMS (Information Management System
Information Management System
IBM Information Management System is a joint hierarchical database and information management system with extensive transaction processing capabilities.- History :...
) manual .
It detailed the PRIME-MODIFIER-CLASS word scheme, which consisted of names like "CUST-ACT-NO" to indicate "customer account number".
PRIME words were meant to indicate major "entities" of interest to a system.
MODIFIER words were used for additional refinement, qualification and readability.
CLASS words ideally would be a very short list of data types relevant to a particular application. Common CLASS words might be: NO (number), ID (identifier), TXT (text), AMT (amount), QTY (quantity), FL (flag), CD (code), W (work) and so forth. In practice, the available CLASS words would be a list of less than two dozen terms.
CLASS words, typically positioned on the right (suffix), served much the same purpose as Hungarian notation
Hungarian notation
Hungarian notation is an identifier naming convention in computer programming, in which the name of a variable or function indicates its type or intended use...
prefixes.
The purpose of CLASS words, in addition to consistency, was to specify to the programmer the data type
Data type
In computer programming, a data type is a classification identifying one of various types of data, such as floating-point, integer, or Boolean, that determines the possible values for that type; the operations that can be done on values of that type; the meaning of the data; and the way values of...
of a particular data field. Prior to the acceptance of BOOLEAN (two values only) fields, FL (flag) would indicate a field with only two possible values.
ActionScript
Adobe's Coding Conventions and Best Practices suggests naming standards for ActionScript
ActionScript
ActionScript is an object-oriented language originally developed by Macromedia Inc. . It is a dialect of ECMAScript , and is used primarily for the development of websites and software targeting the Adobe Flash Player platform, used on Web pages in the form of...
that are mostly consistent with those of ECMAScript
ECMAScript
ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known dialects such as JavaScript, JScript, and ActionScript.- History :JavaScript...
. The style of identifiers is similar to that of Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
Ada is a structured, statically typed, imperative, wide-spectrum, and object-oriented high-level computer programming language, extended from Pascal and other languages...
, the only recommended style of identifiers is Mixed_Case_With_Underscores.
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
In computer programming, a keyword is a word or identifier that has a particular meaning to the programming language. The meaning of keywords — and, indeed, the meaning of the notion of keyword — differs widely from language to language....
A standard library for a programming language is the library that is conventionally made available in every implementation of that language. In some cases, the library is described directly in the programming language specification; in other cases, the contents of the standard library are...
The C Standard Library is the standard library for the programming language C, as specified in the ANSI C standard.. It was developed at the same time as the C POSIX library, which is basically a superset of it...
, abbreviated names are the most common (e.g. isalnum for a function testing whether a character is alphanumeric), while the C++ standard library
C++ standard library
In C++, the C++ Standard Library is a collection of classes and functions, which are written in the core language and part of the C++ ISO Standard itself...
often uses an underscore as a word separator (e.g. out_of_range). Identifiers representing macros are, by convention, written using only upper case letters and underscores (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
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
A standard library for a programming language is the library that is conventionally made available in every implementation of that language. In some cases, the library is described directly in the programming language specification; in other cases, the contents of the standard library are...
) and should not be used (e.g. reserved__ or _Reserved).
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
, naming conventions for identifiers have been established and suggested by various Java communities such as Sun Microsystems, Netscape, AmbySoft etc. A sample of naming conventions set by Sun Microsystem are listed below,
where a name in "CamelCase
CamelCase
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
" is one composed of a number of words joined without spaces, with each word's initial letter in capitals — for example "CamelCase".
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
, with the first letter of every word capitalised. Use whole words — avoid acronyms and abbreviations (unless the abbreviation is much more widely used than the long form, such as URL or HTML).
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
; that is, with the first letter lowercase and the first letters of subsequent words in uppercase.
run;
runFast;
getBackground;
Variables
Local variables, instance variables, and class variables are also written in lowerCamelCase
CamelCase
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
. Variable names should not start with underscore (_) or dollar sign ($) characters, even though both are allowed. Certain coding conventions
Coding conventions
Coding conventions are a set of guidelines for a specific programming language that recommend programming style, practices and methods for each aspect of a piece program written in this language...
state that underscores should be used to prefix all instance variables, for improved reading and program understanding.
Variable names should be short yet meaningful. The choice of a variable name should be mnemonic
Mnemonic
A mnemonic , or mnemonic device, is any learning technique that aids memory. To improve long term memory, mnemonic systems are used to make memorization easier. Commonly encountered mnemonics are often verbal, such as a very short poem or a special word used to help a person remember something,...
— that is, designed to indicate to the casual observer the intent of its use. One-character variable names should be avoided except for temporary "throwaway" variables. Common names for temporary variables are i, j, k, m, and n for integers; c, d, and e for characters.
int i;
char c;
float myWidth;
Constants
Constants should be written in uppercase characters separated by underscores. Constant names may also contain digits if appropriate, but not as the first character.
final static int MAXIMUM_NUM_OF_PARTICIPANTS = 10;
Java compilers do not enforce these rules, but failing to follow them may result in confusion and erroneous code. For example, widget.expand and Widget.expand imply significantly different behaviours. widget.expand implies an invocation to method expand in an instance named widget. Whereas, Widget.expand implies an invocation to static method expand in class Widget.
One widely used Java coding style dictates that UpperCamelCase
CamelCase
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
In object-oriented programming, a class is a construct that is used as a blueprint to create instances of itself – referred to as class instances, class objects, instance objects or simply objects. A class defines constituent members which enable these class instances to have state and behavior...
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
In object-oriented programming an instance is an occurrence or a copy of an object, whether currently executing or not. Instances of a class share the same set of attributes, yet will typically differ in what those attributes contain....
In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...
An integrated development environment is a software application that provides comprehensive facilities to computer programmers for software development...
, such as Eclipse, implement shortcuts based on CamelCase. For instance, in Eclipse's content assist
Content assist
Content/Code assist is functionality of some IDE which helps developer to write code faster and more efficiently. In concrete context of current developer work it provides him list of accessible keywords according to programming language specification, variable, methods, data types, ...- External...
feature, typing just the upper-case letters of a CamelCase word will suggest any matching class or method name (for example, typing "NPE" and activating content assist could suggest "NullPointerException").
Initialisms of three or more letters are CamelCase instead of upper case (e.g., "parseDbmXmlFromIPAddress" instead of "parseDBMXMLFromIPAddress"). One may also set the boundary at two or more letters (e.g., "parseDbmXmlFromIpAddress").
JavaScript
The built-in JavaScript libraries use the same naming conventions as Java. Classes use upper camel case (RegExp, TypeError, XMLHttpRequest, DOMObject) and methods use lower camel case (getElementById, getElementsByTagNameNS, createCDATASection). In order to be consistent most JavaScript developers follow these conventions.
Lisp
Common practice in most Lisp dialects is to use dashes to separate words in identifiers, as in with-open-file and make-hash-table. Global variable names conventionally start and end with asterisks: *map-walls*.
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
(a.k.a. "Pascal Style") for most identifiers. (lowerCamelCase
CamelCase
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
In computer programming, a parameter is a special kind of variable, used in a subroutine to refer to one of the pieces of data provided as input to the subroutine. These pieces of data are called arguments...
In computer programming, a variable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents...
) and is a shared convention for the .NET languages. Microsoft further recommends that no type prefix hints (also known as Hungarian notation
Hungarian notation
Hungarian notation is an identifier naming convention in computer programming, in which the name of a variable or function indicates its type or intended use...
) are used. Instead of using Hungarian notation it is recommended to end the name with the base class' name; LoginButton instead of LoginBtn.
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
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., strict and mro
C3 linearization
In computing, the C3 superclass linearization is an algorithm used primarily to obtain a consistent linearization of a multiple inheritance hierarchy in object-oriented programming. This linearization is used to resolve the order in which methods should be inherited, and is often termed "MRO" for...
Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
recommends UpperCamelCase for class names, CAPITALIZED_WITH_UNDERSCORES for constants, and lowercase_separated_by_underscores for other names.
Ruby is a dynamic, reflective, general-purpose object-oriented programming language that combines syntax inspired by Perl with Smalltalk-like features. Ruby originated in Japan during the mid-1990s and was first developed and designed by Yukihiro "Matz" Matsumoto...
recommends UpperCamelCase for class names, CAPITALIZED_WITH_UNDERSCORES for constants, and lowercase_separated_by_underscores for other names.
Visual Basic is the third-generation event-driven programming language and integrated development environment from Microsoft for its COM programming model...
's naming conventions tend to rest on what is most human-readable, as opposed to providing information about the identifier itself.
Checkstyle is a static code analysis tool used in software development for checking if Java source code complies with coding rules.- Advantages and limits :...
Coding conventions are a set of guidelines for a specific programming language that recommend programming style, practices and methods for each aspect of a piece program written in this language...
In general, a namespace is a container that provides context for the identifiers it holds, and allows the disambiguation of homonym identifiers residing in different namespaces....
A namespace is an abstract container or environment created to hold a logical grouping of unique identifiers or symbols . An identifier defined in a namespace is associated only with that namespace. The same identifier can be independently defined in multiple namespaces...
Onomastics or onomatology is the study of proper names of all kinds and the origins of names. The words are from the Greek: "ὀνομαστικός" , "of or belonging to naming" and "ὀνοματολογία" , from "ὄνομα" "name". Toponymy or toponomastics, the study of place names, is one of the principal branches of...
, the study of names and naming practices, both in the United States and abroad.
Ontology engineering in computer science and information science is a new field, which studies the methods and methodologies for building ontologies: formal representations of a set of concepts within a domain and the relationships between those concepts....
will help to harmonize the appearance and increase the robustness of ontological representational units such as class and relation names within the orthogonal set of OBO Foundry ontologies.
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