API

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For other uses, see API (disambiguation). API_sentence_0

"Api.php" redirects here. API_sentence_1

For the Wikipedia API, see . API_sentence_2

An application programming interface (API) is a computing interface that defines interactions between multiple software intermediaries. API_sentence_3

It defines the kinds of calls or requests that can be made, how to make them, the data formats that should be used, the conventions to follow, etc. API_sentence_4

It can also provide extension mechanisms so that users can extend existing functionality in various ways and to varying degrees. API_sentence_5

An API can be entirely custom, specific to a component, or designed based on an industry-standard to ensure interoperability. API_sentence_6

Through information hiding, APIs enable modular programming, allowing users to use the interface independently of the implementation. API_sentence_7

Purpose API_section_0

In building applications, an API (application programming interface) simplifies programming by abstracting the underlying implementation and only exposing objects or actions the developer needs. API_sentence_8

While a graphical interface for an email client might provide a user with a button that performs all the steps for fetching and highlighting new emails, an API for file input/output might give the developer a function that copies a file from one location to another without requiring that the developer understand the operations occurring behind the scenes. API_sentence_9

History of the term API_section_1

The meaning of the term API has expanded over its history. API_sentence_10

It first described an interface only for end-user-facing programs, known as application programs. API_sentence_11

This origin is still reflected in the name "application programming interface." API_sentence_12

Today, the term API is broader, including also utility software and even hardware interfaces. API_sentence_13

The idea of the API is much older than the term. API_sentence_14

British computer scientists Wilkes and Wheeler worked on modular software libraries in the 1940s for the EDSAC computer. API_sentence_15

Joshua Bloch claims that Wilkes and Wheeler "latently invented" the API, because it is more of a concept that is discovered than invented. API_sentence_16

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. API_sentence_17

The authors of this paper use the term to describe the interaction of an application — a graphics program in this case — with the rest of the computer system. API_sentence_18

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. API_sentence_19

The term was introduced to the field of databases by C. API_sentence_20 J. Date in a 1974 paper called The Relational and Network Approaches: Comparison of the Application Programming Interface. API_sentence_21

An API became a part of ANSI/SPARC framework for database management systems. API_sentence_22

This framework treated the application programming interface separately from other interfaces, such as the query interface. API_sentence_23

Database professionals in the 1970s observed these different interfaces could be combined; a sufficiently rich application interface could support the other interfaces as well. API_sentence_24

This observation lead to APIs that supported all types of programming, not just application programming. API_sentence_25

By 1990, the API was defined simply as "a set of services available to a programmer for performing certain tasks" by technologist Carl Malamud. API_sentence_26

The conception of the API was expanded again with the dawn of web APIs. API_sentence_27

Roy Fielding's dissertation Architectural Styles and the Design of Network-based Software Architectures at UC Irvine in 2000 outlined Representational state transfer (REST) and described the idea of a "network-based Application Programming Interface" that Fielding contrasted with traditional "library-based" APIs. API_sentence_28

XML and JSON web APIs saw widespread commercial adoption beginning in 2000 and continuing as of 2020. API_sentence_29

The web API is now the most common meaning of the term API. API_sentence_30

When used in this way, the term API has some overlap in meaning with the terms communication protocol and remote procedure call. API_sentence_31

Usage API_section_2

Libraries and frameworks API_section_3

An API usually is related to a software library. API_sentence_32

The API describes and prescribes the "expected behavior" (a specification) while the library is an "actual implementation" of this set of rules. API_sentence_33

A single API can have multiple implementations (or none, being abstract) in the form of different libraries that share the same programming interface. API_sentence_34

The separation of the API from its implementation can allow programs written in one language to use a library written in another. API_sentence_35

For example, because Scala and Java compile to compatible bytecode, Scala developers can take advantage of any Java API. API_sentence_36

API use can vary depending on the type of programming language involved. API_sentence_37

An API for a procedural language such as Lua could consist primarily of basic routines to execute code, manipulate data or handle errors while an API for an object-oriented language, such as Java, would provide a specification of classes and its class methods. API_sentence_38

Language bindings are also APIs. API_sentence_39

By mapping the features and capabilities of one language to an interface implemented in another language, a language binding allows a library or service written in one language to be used when developing in another language. API_sentence_40

Tools such as SWIG and F2PY, a Fortran-to-Python interface generator, facilitate the creation of such interfaces. API_sentence_41

An API can also be related to a software framework: a framework can be based on several libraries implementing several APIs, but unlike the normal use of an API, the access to the behavior built into the framework is mediated by extending its content with new classes plugged into the framework itself. API_sentence_42

Moreover, the overall program flow of control can be out of the control of the caller and in the framework's hands by inversion of control or a similar mechanism. API_sentence_43

Operating systems API_section_4

An API can specify the interface between an application and the operating system. API_sentence_44

POSIX, for example, specifies a set of common APIs that aim to enable an application written for a POSIX conformant operating system to be compiled for another POSIX conformant operating system. API_sentence_45

Linux and Berkeley Software Distribution are examples of operating systems that implement the POSIX APIs. API_sentence_46

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". API_sentence_47

An API differs from an application binary interface (ABI) in that an API is source code based while an ABI is based. API_sentence_48

For instance, POSIX provides APIs while the Linux Standard Base provides an ABI. API_sentence_49

Remote APIs API_section_5

Remote APIs allow developers to manipulate remote resources through protocols, specific standards for communication that allow different technologies to work together, regardless of language or platform. API_sentence_50

For example, the Java Database Connectivity API allows developers to query many different types of databases with the same set of functions, while the Java remote method invocation API uses the Java Remote Method Protocol to allow invocation of functions that operate remotely, but appear local to the developer. API_sentence_51

Therefore, remote APIs are useful in maintaining the object abstraction in object-oriented programming; a method call, executed locally on a proxy object, invokes the corresponding method on the remote object, using the remoting protocol, and acquires the result to be used locally as a return value. API_sentence_52

A modification of the proxy object will also result in a corresponding modification of the remote object. API_sentence_53

Web APIs API_section_6

Main article: Web API API_sentence_54

Web APIs are the defined interfaces through which interactions happen between an enterprise and applications that use its assets, which also is a Service Level Agreement (SLA) to specify the functional provider and expose the service path or URL for its API users. API_sentence_55

An API approach is an architectural approach that revolves around providing a program interface to a set of services to different applications serving different types of consumers. API_sentence_56

When used in the context of web development, an API is typically defined as a set of specifications, such as Hypertext Transfer Protocol (HTTP) request messages, along with a definition of the structure of response messages, usually in an Extensible Markup Language (XML) or JavaScript Object Notation (JSON) format. API_sentence_57

An example might be a shipping company API that can be added to an eCommerce-focused website to facilitate ordering shipping services and automatically include current shipping rates, without the site developer having to enter the shipper's rate table into a web database. API_sentence_58

While "web API" historically has been virtually synonymous with web service, the recent trend (so-called Web 2.0) has been moving away from Simple Object Access Protocol (SOAP) based web services and service-oriented architecture (SOA) towards more direct representational state transfer (REST) style web resources and resource-oriented architecture (ROA). API_sentence_59

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. API_sentence_60

Web APIs allow the combination of multiple APIs into new applications known as mashups. API_sentence_61

In the social media space, web APIs have allowed web communities to facilitate sharing content and data between communities and applications. API_sentence_62

In this way, content that is created in one place dynamically can be posted and updated to multiple locations on the web. API_sentence_63

For example, Twitter's REST API allows developers to access core Twitter data and the Search API provides methods for developers to interact with Twitter Search and trends data. API_sentence_64

Design API_section_7

The design of an API has significant impact on its usage. API_sentence_65

The principle of information hiding describes the role of programming interfaces as enabling modular programming by hiding the implementation details of the modules so that users of modules need not understand the complexities inside the modules. API_sentence_66

Thus, the design of an API attempts to provide only the tools a user would expect. API_sentence_67

The design of programming interfaces represents an important part of software architecture, the organization of a complex piece of software. API_sentence_68

Release policies API_section_8

APIs are one of the more common ways technology companies integrate. API_sentence_69

Those that provide and use APIs are considered as being members of a business ecosystem. API_sentence_70

The main policies for releasing an API are: API_sentence_71

API_unordered_list_0

  • Private: The API is for internal company use only.API_item_0_0
  • Partner: Only specific business partners can use the API. For example, vehicle for hire companies such as Uber and Lyft allow approved third-party developers to directly order rides from within their apps. This allows the companies to exercise quality control by curating which apps have access to the API, and provides them with an additional revenue stream.API_item_0_1
  • Public: The API is available for use by the public. For example, Microsoft makes the Windows API public, and Apple releases its API Cocoa, so that software can be written for their platforms. Not all public APIs are generally accessible by everybody. For example, Internet service providers like Cloudflare or Voxility, use RESTful APIs to allow customers and resellers access to their infrastructure information, DDoS stats, network performance or dashboard controls. Access to such APIs is granted either by “API tokens”, or customer status validations.API_item_0_2

Public API implications API_section_9

An important factor when an API becomes public is its "interface stability". API_sentence_72

Changes to the API—for example adding new parameters to a function call—could break compatibility with the clients that depend on that API. API_sentence_73

When parts of a publicly presented API are subject to change and thus not stable, such parts of a particular API should be documented explicitly as "unstable". API_sentence_74

For example, in the Google Guava library, the parts that are considered unstable, and that might change soon, are marked with the Java annotation @Beta. API_sentence_75

A public API can sometimes declare parts of itself as deprecated or rescinded. API_sentence_76

This usually means that part of the API should be considered a candidate for being removed, or modified in a backward incompatible way. API_sentence_77

Therefore, these changes allow developers to transition away from parts of the API that will be removed or not supported in the future. API_sentence_78

Client code may contain innovative or opportunistic usages that were not intended by the API designers. API_sentence_79

In other words, for a library with a significant user base, when an element becomes part of the public API, it may be used in diverse ways. API_sentence_80

On February 19, 2020, Akamai published their annual “State of the Internet” report, showcasing the growing trend of cybercriminals targeting public API platforms at financial services worldwide. API_sentence_81

From December 2017 through November 2019, Akamai witnessed 85.42 billion credential violation attacks. API_sentence_82

About 20%, or 16.55 billion, were against hostnames defined as API endpoints. API_sentence_83

Of these, 473.5 million have targeted financial services sector organizations. API_sentence_84

Documentation API_section_10

API documentation describes what services an API offers and how to use those services, aiming to cover everything a client would need to know for practical purposes. API_sentence_85

Documentation is crucial for the development and maintenance of applications using the API. API_sentence_86

API documentation is traditionally found in documentation files but can also be found in social media such as blogs, forums, and Q&A websites. API_sentence_87

Traditional documentation files are often presented via a documentation system, such as Javadoc or Pydoc, that has a consistent appearance and structure. API_sentence_88

However, the types of content included in the documentation differs from API to API. API_sentence_89

In the interest of clarity, API documentation may include a description of classes and methods in the API as well as "typical usage scenarios, code snippets, design rationales, performance discussions, and contracts", but implementation details of the API services themselves are usually omitted. API_sentence_90

Restrictions and limitations on how the API can be used are also covered by the documentation. API_sentence_91

For instance, documentation for an API function could note that its parameters cannot be null, that the function itself is not thread safe, Because API documentation tends to be comprehensive, it is a challenge for writers to keep the documentation updated and for users to read it carefully, potentially yielding bugs. API_sentence_92

API documentation can be enriched with metadata information like Java annotations. API_sentence_93

This metadata can be used by the compiler, tools, and by the run-time environment to implement custom behaviors or custom handling. API_sentence_94

It is possible to generate API documentation in a data-driven manner. API_sentence_95

By observing many programs that use a given API, it is possible to infer the typical usages, as well the required contracts and directives. API_sentence_96

Then, templates can be used to generate natural language from the mined data. API_sentence_97

Copyright controversy API_section_11

Main article: Oracle America, Inc. v. Google, Inc. API_sentence_98

In 2010, Oracle Corporation sued Google for having distributed a new implementation of Java embedded in the Android operating system. API_sentence_99

Google had not acquired any permission to reproduce the Java API, although permission had been given to the similar OpenJDK project. API_sentence_100

Judge William Alsup ruled in the Oracle v. Google case that APIs cannot be copyrighted in the U.S and that a victory for Oracle would have widely expanded copyright protection and allowed the copyrighting of simple software commands: API_sentence_101

In 2014, however, Alsup's ruling was overturned on appeal to the Court of Appeals for the Federal Circuit, though the question of whether such use of APIs constitutes fair use was left unresolved. API_sentence_102

In 2016, following a two-week trial, a jury determined that Google's reimplementation of the Java API constituted fair use, but Oracle vowed to appeal the decision. API_sentence_103

Oracle won on its appeal, with the Court of Appeals for the Federal Circuit ruling that Google's use of the APIs did not qualify for fair use. API_sentence_104

In 2019, Google appealed to the Supreme Court of the United States over both the copyrightability and fair use rulings, and the Supreme Court granted review. API_sentence_105

Examples API_section_12

Main category: Application programming interfaces API_sentence_106

See also API_section_13

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/API.