Programming language

Thesource codefor a computer program inC.The gray lines arecommentsthat explain the program to humans. Whencompiledandrun,it will give the output "Hello, world!".

Aprogramming languageis a system of notation for writingcomputer programs.

Programming languages are described in terms of theirsyntax(form) andsemantics(meaning), usually defined by aformal language.Languages usually provide features such as atype system,variables,and mechanisms forerror handling.Animplementationof a programming language is required in order toexecuteprograms, namely aninterpreteror acompiler.An interpreter directly executes the source code, while acompilerproduces anexecutableprogram.

Computer architecturehas strongly influenced the design of programming languages, with the most common type (imperative languages—which implement operations in a specified order) developed to perform well on the popularvon Neumann architecture.While early programming languages were closely tied to thehardware,over time they have developed moreabstractionto hide implementation details for greater simplicity.

Thousands of programming languages—often classified as imperative,functional,logic,orobject-oriented—have been developed for a wide variety of uses. Many aspects of programming language design involve tradeoffs—for example,exception handlingsimplifies error handling, but at a performance cost.Programming language theoryis the subfield ofcomputer sciencethat studies the design, implementation, analysis, characterization, and classification of programming languages.

Definitions

There are a variety of criteria that may be considered when defining what constitutes a programming language.

Computer languages vs programming languages

The termcomputer languageis sometimes used interchangeably with programming language.However, the usage of both terms varies among authors, including the exact scope of each. One usage describes programming languages as a subset of computer languages.Similarly, languages used in computing that have a different goal than expressing computer programs are generically designated computer languages. For instance, markup languages are sometimes referred to as computer languages to emphasize that they are not meant to be used for programming. One way of classifying computer languages is by the computations they are capable of expressing, as described by thetheory of computation.The majority of practical programming languages areTuring complete,and all Turing complete languages can implement the same set ofalgorithms.ANSI/ISO SQL-92and Charity are examples of languages that are not Turing complete, yet are often called programming languages.However, some authors restrict the term "programming language" to Turing complete languages.

Another usage regards programming languages as theoretical constructs for programmingabstract machinesand computer languages as the subset thereof that runs on physical computers, which have finite hardware resources.John C. Reynoldsemphasizes thatformal specificationlanguages are just as much programming languages as are the languages intended for execution. He also argues that textual and even graphical input formats that affect the behavior of a computer are programming languages, despite the fact they are commonly not Turing-complete, and remarks that ignorance of programming language concepts is the reason for many flaws in input formats.

Domain and target

In most practical contexts, a programming language involves a computer; consequently, programming languages are usually defined and studied this way.Programming languages differ fromnatural languagesin that natural languages are only used for interaction between people, while programming languages also allow humans to communicate instructions to machines.

The domain of the language is also worth consideration.Markup languageslikeXML,HTML,ortroff,which definestructured data,are not usually considered programming languages.Programming languages may, however, share the syntax with markup languages if a computational semantics is defined.XSLT,for example, is a Turing complete language entirely using XML syntax.Moreover,LaTeX,which is mostly used for structuring documents, also contains a Turing complete subset.

Abstractions

Programming languages usually containabstractionsfor defining and manipulatingdata structuresor controlling theflow of execution.The practical necessity that a programming language supports adequate abstractions is expressed by theabstraction principle.This principle is sometimes formulated as a recommendation to the programmer to make proper use of such abstractions.

History

Early developments

The first programmable computers were invented at the end of the 1940s, and with them, the first programming languages.The earliest computers were programmed infirst-generation programming languages(1GLs),machine language(simple instructions that could be directly executed by the processor). This code was very difficult to debug and was notportablebetween different computer systems.In order to improve the ease of programming,assembly languages(orsecond-generation programming languages—2GLs) were invented, diverging from the machine language to make programs easier to understand for humans, although they did not increase portability.

Initially, hardware resources were scarce and expensive, whilehuman resourceswere cheaper. Therefore, cumbersome languages that were time-consuming to use, but were closer to the hardware for higher efficiency were favored.The introduction ofhigh-level programming languages(third-generation programming languages—3GLs)—revolutionized programming. These languagesabstractedaway the details of the hardware, instead being designed to express algorithms that could be understood more easily by humans. For example, arithmetic expressions could now be written in symbolic notation and later translated into machine code that the hardware could execute.In 1957,Fortran(FORmula TRANslation) was invented. Often considered the firstcompiledhigh-level programming language,Fortran has remained in use into the twenty-first century.

1960s and 1970s

Two people using anIBM 704mainframe—the first hardware to supportfloating-point arithmetic—in 1957.Fortranwas designed for this machine.

Around 1960, the firstmainframes—general purpose computers—were developed, although they could only be operated by professionals and the cost was extreme. The data and instructions were input bypunch cards,meaning that no input could be added while the program was running. The languages developed at this time therefore are designed for minimal interaction.After the invention of themicroprocessor,computers in the 1970s became dramatically cheaper.New computers also allowed more user interaction, which was supported by newer programming languages.

Lisp,implemented in 1958, was the firstfunctional programminglanguage.Unlike Fortran, it supportsrecursionandconditional expressions,and it also introduceddynamic memory managementon aheapand automaticgarbage collection.For the next decades, Lisp dominatedartificial intelligenceapplications.In 1978, another functional language,ML,introducedinferred typesand polymorphicparameters.

AfterALGOL(ALGOrithmic Language) was released in 1958 and 1960,it became the standard in computing literature for describingalgorithms.Although its commercial success was limited, most popular imperative languages—includingC,Pascal,Ada,C++,Java,andC#—are directly or indirectly descended from ALGOL 60.Among its innovations adopted by later programming languages included greater portability and the first use ofcontext-free,BNFgrammar.Simula,the first language to supportobject-oriented programming(includingsubtypes,dynamic dispatch,andinheritance), also descends from ALGOL and achieved commercial success.C, another ALGOL descendant, has sustained popularity into the twenty-first century. C allows access to lower-level machine operations more than other contemporary languages. Its power and efficiency, generated in part with flexiblepointeroperations, comes at the cost of making it more difficult to write correct code.

Prolog,designed in 1972, was the firstlogic programminglanguage, communicating with a computer using formal logic notation.With logic programming, the programmer specifies a desired result and allows theinterpreterto decide how to achieve it.

1980s to 2000s

A small selection of programming language textbooks

During the 1980s, the invention of thepersonal computertransformed the roles for which programming languages were used.New languages introduced in the 1980s included C++, asupersetof C that can compile C programs but also supportsclassesandinheritance.Adaand other new languages introduced support forconcurrency.The Japanese government invested heavily into the so-calledfifth-generation languagesthat added support for concurrency to logic programming constructs, but these languages were outperformed by other concurrency-supporting languages.

Due to the rapid growth of theInternetand theWorld Wide Webin the 1990s, new programming languages were introduced to supportWeb pagesandnetworking.Java,based on C++ and designed for increased portability across systems and security, enjoyed large-scale success because these features are essential for many Internet applications.Another development was that ofdynamically typedscripting languages—Python,JavaScript,PHP,andRuby—designed to quickly produce small programs that coordinate existingapplications.Due to their integration withHTML,they have also been used for building web pages hosted onservers.

2000s to present

During the 2000s, there was a slowdown in the development of new programming languages that achieved widespread popularity.One innovation wasservice-oriented programming,designed to exploitdistributed systemswhose components are connected by a network. Services are similar to objects in object-oriented programming, but run on a separate process.C#andF#cross-pollinated ideas between imperative and functional programming.After 2010, several new languages—Rust,Go,Swift,ZigandCarbon—competed for the performance-critical software for which C had historically been used.Most of the new programming languages usesstatic typingwhile a few numbers of new languages usedynamic typinglikeRingandJulia.

Some of the new programming languages are classified asvisual programming languageslikeScratch,LabVIEWandPWCT.Also, some of these languages mix between textual and visual programming usage likeBallerina.Also, this trend lead to developing projects that help in developing new VPLs likeBlocklybyGoogle.Many game engines likeUnrealandUnityadded support for visual scripting too.

Elements

Every programming language includes fundamental elements for describing data and the operations or transformations applied to them, such as adding two numbers or selecting an item from a collection. These elements are governed by syntactic and semantic rules that define their structure and meaning, respectively.

Syntax

Main article:Syntax (programming languages)

Parse treeofPython codewith inset tokenization

Syntax highlightingis often used to aid programmers in recognizing elements of source code. The language above isPython.

A programming language's surface form is known as itssyntax.Most programming languages are purely textual; they use sequences of text including words, numbers, and punctuation, much like written natural languages. On the other hand, some programming languages aregraphical,using visual relationships between symbols to specify a program.

The syntax of a language describes the possible combinations of symbols that form a syntactically correct program. The meaning given to a combination of symbols is handled by semantics (eitherformalor hard-coded in areference implementation). Since most languages are textual, this article discusses textual syntax.

The programming language syntax is usually defined using a combination ofregular expressions(forlexicalstructure) andBackus–Naur form(forgrammaticalstructure). Below is a simple grammar, based onLisp:

expression::=atom | list
atom::=number | symbol
number::=[+-]?['0'-'9']+
symbol::=['A'-'Z''a'-'z'].*
list::='(' expression* ')'

This grammar specifies the following:

• anexpressionis either anatomor alist;
• anatomis either anumberor asymbol;
• anumberis an unbroken sequence of one or more decimal digits, optionally preceded by a plus or minus sign;
• asymbolis a letter followed by zero or more of any characters (excluding whitespace); and
• alistis a matched pair of parentheses, with zero or moreexpressionsinside it.

The following are examples of well-formed token sequences in this grammar:12345,()and(a b c232 (1)).

Not all syntactically correct programs are semantically correct. Many syntactically correct programs are nonetheless ill-formed, per the language's rules; and may (depending on the language specification and the soundness of the implementation) result in an error on translation or execution. In some cases, such programs may exhibitundefined behavior.Even when a program is well-defined within a language, it may still have a meaning that is not intended by the person who wrote it.

Usingnatural languageas an example, it may not be possible to assign a meaning to a grammatically correct sentence or the sentence may be false:

• "Colorless green ideas sleep furiously."is grammatically well-formed but has no generally accepted meaning.
• "John is a married bachelor." is grammaticallywell-formedbut expresses a meaning that cannot be true.

The followingC languagefragment is syntactically correct, but performs operations that are not semantically defined (the operation*p >> 4has no meaning for a value having a complex type andp->imis not defined because the value ofpis thenull pointer):

complex*p=NULL;
complexabs_p=sqrt(*p>>4+p->im);

If thetype declarationon the first line were omitted, the program would trigger an error on the undefined variablepduring compilation. However, the program would still be syntactically correct since type declarations provide only semantic information.

The grammar needed to specify a programming language can be classified by its position in theChomsky hierarchy.The syntax of most programming languages can be specified using a Type-2 grammar, i.e., they arecontext-free grammars.Some languages, including Perl and Lisp, contain constructs that allow execution during the parsing phase. Languages that have constructs that allow the programmer to alter the behavior of the parser make syntax analysis anundecidable problem,and generally blur the distinction between parsing and execution.In contrast toLisp's macro systemand Perl'sBEGINblocks, which may contain general computations, C macros are merely string replacements and do not require code execution.

Semantics

The termsemanticsrefers to the meaning of languages, as opposed to their form (syntax).

Static semantics

Static semantics defines restrictions on the structure of valid texts that are hard or impossible to express in standard syntactic formalisms.For compiled languages, static semantics essentially include those semantic rules that can be checked at compile time. Examples include checking that everyidentifieris declared before it is used (in languages that require such declarations) or that the labels on the arms of acase statementare distinct.Many important restrictions of this type, like checking that identifiers are used in the appropriate context (e.g. not adding an integer to a function name), or thatsubroutinecalls have the appropriate number and type of arguments, can be enforced by defining them as rules in alogiccalled atype system.Other forms ofstatic analyseslikedata flow analysismay also be part of static semantics. Programming languages such asJavaandC#havedefinite assignment analysis,a form of data flow analysis, as part of their respective static semantics.

Dynamic semantics

Main article:Semantics of programming languages

Once data has been specified, the machine must be instructed to perform operations on the data. For example, the semantics may define thestrategyby which expressions are evaluated to values, or the manner in whichcontrol structuresconditionally executestatements.Thedynamic semantics(also known asexecution semantics) of a language defines how and when the various constructs of a language should produce a program behavior. There are many ways of defining execution semantics. Natural language is often used to specify the execution semantics of languages commonly used in practice. A significant amount of academic research goes intoformal semantics of programming languages,which allows execution semantics to be specified in a formal manner. Results from this field of research have seen limited application to programming language design and implementation outside academia.

Type system

Main articles:Data type,Type system,andType safety

Adata typeis a set of allowable values and operations that can be performed on these values.Each programming language'stype systemdefines which data types exist, the type of anexpression,and howtype equivalenceandtype compatibilityfunction in the language.

According totype theory,a language is fully typed if the specification of every operation defines types of data to which the operation is applicable.In contrast, an untyped language, such as mostassembly languages,allows any operation to be performed on any data, generally sequences of bits of various lengths.In practice, while few languages are fully typed, most offer a degree of typing.

Because different types (such asintegersandfloats) represent values differently, unexpected results will occur if one type is used when another is expected.Type checkingwill flag this error, usually atcompile time(runtime type checking is more costly).Withstrong typing,type errorscan always be detected unless variables are explicitlycastto a different type.Weak typingoccurs when languages allow implicit casting—for example, to enable operations between variables of different types without the programmer making an explicit type conversion. The more cases in which thistype coercionis allowed, the fewer type errors can be detected.

Commonly supported types

See also:Primitive data type

Early programming languages often supported only built-in, numeric types such as theinteger(signed and unsigned) andfloating point(to support operations onreal numbersthat are not integers). Most programming languages support multiple sizes of floats (often calledfloatanddouble) and integers depending on the size and precision required by the programmer. Storing an integer in a type that is too small to represent it leads tointeger overflow.The most common way of representing negative numbers with signed types istwos complement,althoughones complementis also used.Other common types includeBoolean—which is either true or false—andcharacter—traditionally onebyte,sufficient to represent allASCIIcharacters.

Arraysare a data type whose elements, in many languages, must consist of a single type of fixed length. Other languages define arrays as references to data stored elsewhere and support elements of varying types.Depending on the programming language, sequences of multiple characters, calledstrings,may be supported as arrays of characters or their ownprimitive type.Strings may be of fixed or variable length, which enables greater flexibility at the cost of increased storage space and more complexity.Other data types that may be supported includelists,associative (unordered) arraysaccessed via keys,recordsin which data is mapped to names in an ordered structure,andtuples—similar to records but without names for data fields.Pointersstore memory addresses, typically referencing locations on theheapwhere other data is stored.

The simplestuser-defined typeis anordinal typewhose values can be mapped onto the set of positive integers.Since the mid-1980s, most programming languages also supportabstract data types,in which the representation of the data and operations arehidden from the user,who can only access aninterface.The benefits ofdata abstractioncan include increased reliability, reduced complexity, less potential forname collision,and allowing the underlyingdata structureto be changed without the client needing to alter its code.

Static and dynamic typing

Instatic typing,all expressions have their types determined before a program executes, typically at compile-time.Most widely used, statically typed programming languages require the types of variables to be specified explicitly. In some languages, types are implicit; one form of this is when the compiler caninfertypes based on context. The downside ofimplicit typingis the potential for errors to go undetected.Complete type inference has traditionally been associated with functional languages such asHaskellandML.

With dynamic typing, the type is not attached to the variable but only the value encoded in it. A single variable can be reused for a value of a different type. Although this provides more flexibility to the programmer, it is at the cost of lower reliability and less ability for the programming language to check for errors.Some languages allow variables of aunion typeto which any type of value can be assigned, in an exception to their usual static typing rules.

Concurrency

See also:Concurrent computing

In computing, multiple instructions can be executed simultaneously. Many programming languages support instruction-level and subprogram-level concurrency.By the twenty-first century, additional processing power on computers was increasingly coming from the use of additional processors, which requires programmers to design software that makes use of multiple processors simultaneously to achieve improved performance.Interpreted languagessuch asPythonandRubydo not support the concurrent use of multiple processors.Other programming languages do support managing data shared between different threads by controlling the order of execution of key instructions via the use ofsemaphores,controlling access to shared data viamonitor,or enablingmessage passingbetween threads.

Exception handling

Main article:Exception handling

Many programming languages include exception handlers, a section of code triggered byruntime errorsthat can deal with them in two main ways:

• Termination: shutting down and handing over control to theoperating system.This option is considered the simplest.
• Resumption: resuming the program near where the exception occurred. This can trigger a repeat of the exception, unless the exception handler is able to modify values to prevent the exception from reoccurring.

Some programming languages support dedicating a block of code to run regardless of whether an exception occurs before the code is reached; this is called finalization.

There is a tradeoff between increased ability to handle exceptions and reduced performance.For example, even though array index errors are commonC does not check them for performance reasons.Although programmers can write code to catch user-defined exceptions, this can clutter a program. Standard libraries in some languages, such as C, use their return values to indicate an exception.Some languages and their compilers have the option of turning on and off error handling capability, either temporarily or permanently.

Design and implementation

Main article:Programming language design and implementation

One of the most important influences on programming language design has beencomputer architecture.Imperative languages,the most commonly used type, were designed to perform well onvon Neumann architecture,the most common computer architecture.In von Neumann architecture, thememorystores both data and instructions, while theCPUthat performs instructions on data is separate, and data must be piped back and forth to the CPU. The central elements in these languages are variables,assignment,anditeration,which is more efficient thanrecursionon these machines.

Many programming languages have been designed from scratch, altered to meet new needs, and combined with other languages. Many have eventually fallen into disuse.The birth of programming languages in the 1950s was stimulated by the desire to make a universal programming language suitable for all machines and uses, avoiding the need to write code for different computers.By the early 1960s, the idea of a universal language was rejected due to the differing requirements of the variety of purposes for which code was written.

Tradeoffs

Desirable qualities of programming languages include readability, writability, and reliability.These features can reduce the cost of training programmers in a language, the amount of time needed to write and maintain programs in the language, the cost of compiling the code, and increase runtime performance.

• Although early programming languages often prioritized efficiency over readability, the latter has grown in importance since the 1970s. Having multiple operations to achieve the same result can be detrimental to readability, as isoverloading operators,so that the same operator can have multiple meanings.Another feature important to readability isorthogonality,limiting the number of constructs that a programmer has to learn.A syntax structure that is easily understood andspecial wordsthat are immediately obvious also supports readability.
• Writability is the ease of use for writing code to solve the desired problem. Along with the same features essential for readability,abstraction—interfaces that enable hiding details from the client—andexpressivity—enabling more concise programs—additionally help the programmer write code.The earliest programming languages were tied very closely to the underlying hardware of the computer, but over time support for abstraction has increased, allowing programmers express ideas that are more remote from simple translation into underlying hardware instructions. Because programmers are less tied to the complexity of the computer, their programs can do more computing with less effort from the programmer.Most programming languages come with astandard libraryof commonly used functions.
• Reliability means that a program performs as specified in a wide range of circumstances.Type checking,exception handling,and restrictedaliasing(multiple variable names accessing the same region of memory) all can improve a program's reliability.

Programming language design often involves tradeoffs.For example, features to improve reliability typically come at the cost of performance.Increased expressivity due to a large number of operators makes writing code easier but comes at the cost of readability.

Natural-language programminghas been proposed as a way to eliminate the need for a specialized language for programming. However, this goal remains distant and its benefits are open to debate.Edsger W. Dijkstratook the position that the use of a formal language is essential to prevent the introduction of meaningless constructs.Alan Perliswas similarly dismissive of the idea.

Specification

Main article:Programming language specification

The specification of a programming language is an artifact that the languageusersand theimplementorscan use to agree upon whether a piece ofsource codeis a validprogramin 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 innatural language(e.g., as in theC language), or aformal semantics(e.g., as inStandard MLandSchemespecifications).
• A description of the behavior of atranslatorfor the language (e.g., theC++andFortranspecifications). The syntax and semantics of the language have to be inferred from this description, which may be written in natural or formal language.
• Areferenceormodelimplementation,sometimeswritten in the language being specified(e.g.,PrologorANSI REXX). The syntax and semantics of the language are explicit in the behavior of the reference implementation.

Implementation

Main article:Programming language implementation

An implementation of a programming language is the conversion of a program intomachine codethat can be executed by the hardware. The machine code then can be executed with the help of theoperating system.The most common form of interpretation inproduction codeis by acompiler,which translates the source code via an intermediate-level language into machine code, known as anexecutable.Once the program is compiled, it will run more quickly than with other implementation methods.Some compilers are able to provide furtheroptimizationto reduce memory or computation usage when the executable runs, but increasing compilation time.

Another implementation method is to run the program with aninterpreter,which translates each line of software into machine code just before it executes. Although it can make debugging easier, the downside of interpretation is that it runs 10 to 100 times slower than a compiled executable.Hybrid interpretation methods provide some of the benefits of compilation and some of the benefits of interpretation via partial compilation. One form this takes isjust-in-time compilation,in which the software is compiled ahead of time into an intermediate language, and then into machine code immediately before execution.

Proprietary languages

Although most of the most commonly used programming languages have fully open specifications and implementations, many programming languages exist only as proprietary programming languages with the implementation available only from a single vendor, which may claim that such a proprietary language is their intellectual property. Proprietary programming languages are commonlydomain-specific languagesor internalscripting languagesfor a single product; some proprietary languages are used only internally within a vendor, while others are available to external users.

Some programming languages exist on the border between proprietary and open; for example,Oracle Corporationasserts proprietary rights to some aspects of theJava programming language,andMicrosoft'sC#programming language, which has open implementations of most parts of the system, also hasCommon Language Runtime(CLR) as a closed environment.

Many proprietary languages are widely used, in spite of their proprietary nature; examples includeMATLAB,VBScript,andWolfram Language.Some languages may make the transition from closed to open; for example,Erlangwas originally Ericsson's internal programming language.

Open source programming languages are particularly helpful foropen scienceapplications, enhancing the capacity forreplicationand code sharing.

Use

Thousands of different programming languages have been created, mainly in the computing field. Individual software projects commonly use five programming languages or more.

Programming languages differ from most other forms of human expression in that they require a greater degree of precision and completeness. When using a natural language to communicate with other people, human authors and speakers can be ambiguous and make small errors, and still expect their intent to be understood. However, figuratively speaking, computers "do exactly what they are told to do", and cannot "understand" what code the programmer intended to write. The combination of the language definition, a program, and the program's inputs must fully specify the external behavior that occurs when the program is executed, within the domain of control of that program. On the other hand, ideas about an algorithm can be communicated to humans without the precision required for execution by usingpseudocode,which interleaves natural language with code written in a programming language.

A programming language provides a structured mechanism for defining pieces of data, and the operations or transformations that may be carried out automatically on that data. Aprogrammeruses theabstractionspresent in the language to represent the concepts involved in a computation. These concepts are represented as a collection of the simplest elements available (calledprimitives).Programmingis the process by which programmers combine these primitives to compose new programs, or adapt existing ones to new uses or a changing environment.

Programs for a computer might beexecutedin abatch processwithout human interaction, or a user might typecommandsin aninteractive sessionof aninterpreter.In this case the "commands" are simply programs, whose execution is chained together. When a language can run its commands through an interpreter (such as aUnix shellor othercommand-line interface), without compiling, it is called ascripting language.

Measuring language usage

Determining which is the most widely used programming language is difficult since the definition of usage varies by context. One language may occupy the greater number of programmer hours, a different one has more lines of code, and a third may consume the most CPU time. Some languages are very popular for particular kinds of applications. For example,COBOLis still strong in the corporate data center, often on largemainframes;Fortranin scientific and engineering applications;Adain aerospace, transportation, military, real-time, and embedded applications; andCin embedded applications and operating systems. Other languages are regularly used to write many different kinds of applications.

Various methods of measuring language popularity, each subject to a different bias over what is measured, have been proposed:

• counting the number of job advertisements that mention the language
• the number of books sold that teach or describe the language
• estimates of the number of existing lines of code written in the language – which may underestimate languages not often found in public searches
• counts of language references (i.e., to the name of the language) found using a web search engine.

Combining and averaging information from various internet sites, stackify reported the ten most popular programming languages (in descending order by overall popularity):Java,C,C++,Python,C#,JavaScript,VB.NET,R,PHP,andMATLAB.

As of June 2024, the top five programming languages as measured byTIOBE indexarePython,C++,C,JavaandC#.TIOBE provide a list of top 100 programming languages according to popularity and update this list every month.

Dialects, flavors and implementations

Adialectof a programming language or adata exchange languageis a (relatively small) variation or extension of the language that does not change its intrinsic nature. With languages such asSchemeandForth,standards may be considered insufficient, inadequate, or illegitimate by implementors, so often they will deviate from the standard, making a newdialect.In other cases, a dialect is created for use in adomain-specific language,often a subset. In theLispworld, most languages that use basicS-expressionsyntax and Lisp-like semantics are considered Lisp dialects, although they vary wildly as do, say,RacketandClojure.As it is common for one language to have several dialects, it can become quite difficult for an inexperienced programmer to find the right documentation. TheBASIClanguage hasmany dialects.

Classifications

Further information:Categorical list of programming languages

Programming languages are often placed into four main categories:imperative,functional,logic,andobject oriented.

• Imperative languages are designed to implement an algorithm in a specified order; they includevisual programming languagessuch as.NETfor generatinggraphical user interfaces.Scripting languages,which are partly or fullyinterpretedrather thancompiled,are sometimes considered a separate category but meet the definition of imperative languages.
• Functional programming languages work by successively applying functions to the given parameters. Although appreciated by many researchers for their simplicity and elegance, problems with efficiency have prevented them from being widely adopted.
• Logic languages are designed so that the software, rather than the programmer, decides what order in which the instructions are executed.
• Object-oriented programming—whose characteristic features aredata abstraction,inheritance,anddynamic dispatch—is supported by most popular imperative languages and some functional languages.

Althoughmarkup languagesare not programming languages, some have extensions that support limited programming. Additionally, there are special-purpose languages that are not easily compared to other programming languages.

See also

• Comparison of programming languages (basic instructions)
• Comparison of programming languages
• Computer programming
• Computer scienceandOutline of computer science
• Domain-specific language
• Domain-specific modeling
• Educational programming language
• Esoteric programming language
• Extensible programming
• Category:Extensible syntax programming languages
• Invariant-based programming
• List of BASIC dialects
• Lists of programming languages
• List of programming language researchers
• Programming languages used in most popular websites
• Language-oriented programming
• Logic programming
• Literate programming
• Metaprogramming
  • Ruby (programming language) § Metaprogramming
• Modeling language
• Programming language theory
• Pseudocode
• Rebol § Dialects
• Reflective programming
• Scientific programming language
• Scripting language
• Software engineeringandList of software engineering topics

Further reading

See also:History of programming languages § Further reading

• Abelson, Harold;Sussman, Gerald Jay(1996).Structure and Interpretation of Computer Programs(2nd ed.). MIT Press. Archived fromthe originalon 9 March 2018.
• Raphael Finkel:Advanced Programming Language Design,Addison Wesley 1995.
• Daniel P. Friedman,Mitchell Wand,Christopher T. Haynes:Essentials of Programming Languages,The MIT Press 2001.
• David Gelernter,Suresh Jagannathan:Programming Linguistics,The MIT Press1990.
• Ellis Horowitz(ed.):Programming Languages, a Grand Tour(3rd ed.), 1987.
• Ellis Horowitz:Fundamentals of Programming Languages,1989.
• Shriram Krishnamurthi:Programming Languages: Application and Interpretation,online publicationArchived30 April 2021 at theWayback Machine.
• Gabbrielli, Maurizio; Martini, Simone (2023).Programming Languages: Principles and Paradigms(2nd ed.). Springer.ISBN978-3-031-34144-1.
• Bruce J. MacLennan:Principles of Programming Languages: Design, Evaluation, and Implementation,Oxford University Press1999.
• John C. Mitchell:Concepts in Programming Languages,Cambridge University Press2002.
• Nofre, David; Priestley, Mark; Alberts, Gerard (2014)."When Technology Became Language: The Origins of the Linguistic Conception of Computer Programming, 1950–1960".Technology and Culture.55(1): 40–75.doi:10.1353/tech.2014.0031.ISSN0040-165X.JSTOR24468397.PMID24988794.
• Benjamin C. Pierce:Types and Programming Languages,The MIT Press 2002.
• Terrence W. PrattandMarvin Victor Zelkowitz:Programming Languages: Design and Implementation(4th ed.), Prentice Hall 2000.
• Peter H. Salus.Handbook of Programming Languages(4 vols.). Macmillan 1998.
• Ravi Sethi:Programming Languages: Concepts and Constructs,2nd ed.,Addison-Wesley1996.
• Michael L. Scott:Programming Language Pragmatics,Morgan Kaufmann Publishers2005.
• Sebesta, Robert W. (2012).Concepts of Programming Languages(10 ed.). Addison-Wesley.ISBN978-0-13-139531-2.
• Franklyn Turbak and David Gifford with Mark Sheldon:Design Concepts in Programming Languages,The MIT Press 2009.
• Peter Van RoyandSeif Haridi.Concepts, Techniques, and Models of Computer Programming,The MIT Press 2004.
• David A. Watt.Programming Language Concepts and Paradigms.Prentice Hall 1990.
• David A. Watt andMuffy Thomas.Programming Language Syntax and Semantics.Prentice Hall 1991.
• David A. Watt.Programming Language Processors.Prentice Hall 1993.
• David A. Watt.Programming Language Design Concepts.John Wiley & Sons 2004.
• Wilson, Leslie B. (2001).Comparative Programming Languages, Third Edition.Addison-Wesley.ISBN0-201-71012-9.

See also

• {{Computer language}}
• {{Programming languages}}
• {{Programming paradigms navbox}}