API: Difference between revisions

Revision as of 22:23, 28 March 2025

Latest revision as of 04:31, 28 August 2025

(45 intermediate revisions by 30 users not shown)

Line 3:

{{hatnote|"Api.php" redirects here. For the Wikipedia API, see {{Plain link|[Special:ApiHelp]}}.|selfref=true}}

An '''Applicationapplication Programmingprogramming Interfaceinterface''' ('''API''') is a connection between computers[[computer]]s or between [[computer programsprogram]]s. It is a type of software [[Interface (computing)|interface]], offering a service to other pieces of [[software]].<ref name=":0">{{cite book |last=Reddy |first=Martin |author-link= |date=2011 |title=API Design for C++ |url=https://books.google.com/books?id=IY29LylT85wC |publisher=Elsevier Science |page=1 |isbn=9780123850041}}</ref> A document or standard that describes how to build such a connection or interface is called an ''API specification''. A computer system that meets this standard is said to ''implement'' or ''expose'' an API. The term API may refer either to the specification or to the implementation.

In contrast to a [[user interface]], which connects a computer to a person, an application programming interface connects computers or pieces of software to each other. It is not intended to be used directly by a person (the [[end user]]) other than a [[computer programmer]]<ref name=":0">{{cite book |last=Reddy |first=Martin |author-link= |url=https://books.google.com/books?id=IY29LylT85wC |title=API Design for C++ |date=2011 |publisher=Elsevier Science |isbn=9780123850041 |page=1}}</ref> who is incorporating it into software. An API is often made up of different parts which act as tools or services that are available to the programmer. A program or a programmer that uses one of these parts is said to ''call'' that portion of the API. The calls that make up the API are also known as subroutines[[subroutine]]s, methods, requests, or endpoints[[communication endpoint|endpoint]]s. An API specification ''defines'' these calls, meaning that it explains how to use or implement them.

One purpose of APIs is to [[information hiding|hide the internal details]] of how a system works, exposing only those parts a programmer will find useful and keeping them consistent even if the internal details later change. An API may be custom-built for a particular pair of systems, or it may be a shared standard allowing [[interoperability]] among many systems.

The term API is often used to refer to web APIs, which allow communication between computers that are joined by the internet. There are also APIs for programming languages, software libraries, computer operating systems, and computer hardware. APIs originated in the 1940s, though the term did not emerge until the 1960s and 70s.

The term API is often used to refer to [[web APIsAPI]]s,<ref name="Lane2019"/> which allow communication between computers that are joined by the [[internet]]. There are also APIs for [[programming languageslanguage]]s, [[library (computing)|software libraries]], computer [[operating systemssystem]]s, and [[computer hardware]]. APIs originated in the 1940s, though the term did not emerge until the 1960s and 70s.

== Purpose ==

Line 32 ⟶ 34:

[[File:Univac 1108 Census Bureau.jpg|thumb|300px|Although the people who coined the term API were implementing software on a [[UNIVAC 1100/2200 series#1108|Univac 1108]], the goal of their API was to make [[hardware independent]] programs possible.<ref name="CottonGreatorex1968" />]]

The term "application program interface" (without an ''-ing'' suffix) is first recorded in a paper called ''Data structures and techniques for remote [[computer graphics]]'' presented at an [[AFIPS]] conference in 1968.<ref>{{Cite OED|application program interface}}</ref><ref name="Bloch2018" /> The authors of this paper use the term to describe the interaction of an [[application software|application]]—a graphics program in this case—with the rest of the computer system. A consistent application interface (consisting of [[Fortran]] subroutine calls) was intended to free the programmer from dealing with idiosyncrasies of the graphics display device, and to provide [[hardware independence]] if the computer or the display were replaced.<ref name="CottonGreatorex1968">{{cite conference |url=https://www.computer.org/csdl/pds/api/csdl/proceedings/download-article/12OmNyRPgFZ/pdf |title=Data structures and techniques for remote computer graphics |last1=Cotton |first1=Ira W. |last2=Greatorex |first2=Frank S. |date=December 1968 |conference=AFIPS 1968 Fall Joint Computer Conference |volume=I |book-title=AFIPS '68: Proceedings of the December 9–11, 1968, Fall Joint Computer Conference |publisher=Association for Computing Machinery |___location=San Francisco, California |pages=533–544 |isbn=978-1450378994 |oclc= 1175621908 |doi=10.1145/1476589.1476661 |url-access=subscription }}</ref>

The term was introduced to the field of [[database]]s by [[Christopher J. Date|C. J. Date]]<ref>{{cite book |last=Date |first=C. J. |author-link=Christopher J. Date |year=2019 |title=E. F. Codd and Relational Theory: A Detailed Review and Analysis of Codd's Major Database Writings |url=https://books.google.com/books?id=2Sy4DwAAQBAJ&pg=PA135 |page=135 |publisher=Lulu.com |isbn=978-1684705276}}</ref> in a 1974 paper called ''The [[Relational database|Relational]] and [[Network model|Network]] Approaches: Comparison of the Application Programming Interface''.<ref>{{cite conference |url=https://dl.acm.org/doi/pdf/10.1145/800297.811532 |title=The relational and network approaches: Comparison of the application programming interfaces |last1=Date |first1=C. J. |last2=Codd |first2=E. F. |date=January 1975 |editor=Randall Rustin |conference=SIGMOD Workshop 1974 |volume=2 |book-title=Proceedings of 1974 ACM-SIGMOD Workshop on Data Description, Access and Control |publisher=Association for Computing Machinery |___location=Ann Arbor, Michigan |pages=83–113 |isbn=978-1450374187 |oclc=1175623233 |doi=10.1145/800297.811532 |url-access=subscription }}</ref> An API became a part of the [[ANSI-SPARC Architecture|ANSI/SPARC framework]] for [[database management system]]s. This framework treated the application programming interface separately from other interfaces, such as the query interface. Database professionals in the 1970s observed these different interfaces could be combined; a sufficiently rich application interface could support the other interfaces as well.<ref name="NBS1981">{{cite report |date=April 1981 |title=Database architectures – a feasibility workshop |url=https://hdl.handle.net/2027/mdp.39015077587742?urlappend=%3Bseq=53 |publisher=U.S. Department of Commerce, National Bureau of Standards |pages=45–47 |access-date=September 18, 2020 |___location=Washington, DC|hdl=2027/mdp.39015077587742?urlappend=%3Bseq=53 |id=NBS special publication 500-76 |lccn=81600004}}</ref>

This observation led to APIs that supported all types of programming, not just application programming. By 1990, the API was defined simply as "a set of services available to a programmer for performing certain tasks" by technologist [[Carl Malamud]].<ref>{{cite book |last=Carl |first=Malamud |author-link=Carl Malamud |date=1990 |title=Analyzing Novell Networks |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015018454903&seq=314 |publisher=Van Nostrand Reinhold |page=294 |isbn=978-0442003647}}</ref>

Line 74 ⟶ 76:

}}

</ref>

===Operating systems===

Line 80 ⟶ 83:

[[Linux]] and [[Berkeley Software Distribution]] are examples of operating systems that implement the POSIX APIs.<ref name="WestDedrick16">{{Cite journal |last1=West |first1=Joel |last2=Dedrick |first2=Jason |date=2001 |title=Open source standardization: the rise of Linux in the network era |url=http://www.joelwest.org/Papers/WestDedrick2001b.pdf |journal=Knowledge, Technology & Policy |volume=14 |issue=2 |pages=88–112 |doi=10.1007/PL00022278 |access-date=2 August 2016}}</ref>

[[Microsoft]] has shown a strong commitment to a backward-compatible API, particularly within its [[Windows API]] (Win32) library, so older applications may run on newer versions of Windows using an executable-specific setting called "Compatibility Mode".<ref>

{{cite web

|author=Microsoft

Line 91 ⟶ 94:

|archive-url=https://web.archive.org/web/20090926235439/http://www.microsoft.com/windowsxp/using/helpandsupport/learnmore/appcompat.mspx

|archive-date=2009-09-26

}}</ref> How much Microsoft developers' access to the company's operating systems' internal APIs is an advantage is unclear. Richard A. Shaffer of ''Technologic Computer Letter'' in 1987 compared the situation to a baseball game in which "Microsoft owns all the bats and the field",<ref name="barney19871102">{{Cite magazine |last=Barney |first=Douglas |date=1987-11-02 |title=Balancing on the high wire of Microsoft's success |url=https://books.google.com/books?id=mUSIMiurpfYC&pg=PP81 |access-date=2025-06-08 |magazine=Computerworld |page=SR15 |volume=XXI |issue=44}}</ref> but [[Ed Esber]] of [[Ashton-Tate]] said in an interview that year that [[Bill Gates]] told him that his developers sometimes had to rewrite software based on early APIs. Gates noted in the interview that Microsoft's [[Apple Macintosh]] applications were more successful than those for MS-DOS, because his company did not have to also devote resources to [[Classic Mac OS|Mac OS]].<ref name="computerworld19871102interview">{{Cite interview |last=Gates |first=Bill |interviewer=Paul Gillin |title=The great software debate |last2=Manzi |first2=Jim |last3=Esber |first3=Ed |url=https://books.google.com/books?id=mUSIMiurpfYC&pg=PP73 |access-date=2025-06-08 |work=Computerworld |issue=44 |date=1987-11-02 |page=SR7 |volume=XXI}}</ref>

}}</ref>

An API differs from an [[application binary interface]] (ABI) in that an API is source code based while an ABI is [[Binary file|binary]] based. For instance, [[POSIX]] provides APIs while the [[Linux Standard Base]] provides an ABI.<ref>{{cite web|

Line 147 ⟶ 150:

|year = 2008

|access-date = 2019-10-01

|url-access= subscription

}}</ref> Part of this trend is related to the [[Semantic Web]] movement toward [[Resource Description Framework]] (RDF), a concept to promote web-based [[ontology engineering]] technologies. Web APIs allow the combination of multiple APIs into new applications known as [[mashup (web application hybrid)|mashup]]s.<ref>{{citation

|first = James

|last = Niccolai

Line 255 ⟶ 259:

*[[Comparison of application virtual machines]]

*[[Document Object Model]] (DOM)

*[[Double-chance function]]

*[[Foreign function interface]]

*[[Front and back ends]]