Interface (computing): Difference between revisions

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{{shortShort description|ConceptShared ofboundary computerbetween science; pointelements of interaction betweena twocomputing thingssystem}}

{{Refimprove|date=May 2010}}

In computing, an '''interface''' is a shared boundary across which two or more separate components of a [[computer system]] exchange information. The exchange can be between [[software]], [[computer hardware]], [[peripheral]]|peripheral devices]], [[User interface|humans]], and combinations of these.<ref name="HookwayInterface14">{{cite book |url=https://books.google.com/books?id=BQM_AwAAQBAJ |chapter=Chapter 1: The Subject of the Interface |title=Interface |author=Hookway, B. |publisher=MIT Press |pages=1–58 |year=2014 |isbn=9780262525503}}</ref> Some computer hardware devices, such as a [[touchscreen]], can both send and receive data through the interface, while others such as a mouse or microphone may only provide an interface to send data to a given system.<ref>{{cite encyclopedia

| year = 2000

| title = IEEE 100 - The Authoritative Dictionary Of IEEE Standards Terms

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== Hardware interfaces ==

[[File:RJ-45 Ethernet socket on Lenovo T410 Laptop.jpg|thumb|upright=1.4|Hardware interfaces of a [[Laptoplaptop]] computer: [[Ethernet]] network socket (center), to the left a part of the [[Video Graphics Array|VGA]] port, to the right (upper) a [[display port]] socket, to the right (lower) a [[Universal Serial Bus|USB]]-BA socket.]]

{{Main article|Hardware interface}}

Hardware interfaces exist in many components, such as the various [[Bus (computing)|buses]], [[Computer data storage|storage devices]], other [[I/O]] devices, etc. A hardware interface is described by the mechanical, electrical, and logical signals at the interface and the protocol for sequencing them (sometimes called signaling).<ref name="87Blaauw">

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{{See also|Application binary interface|Application programming interface}}

A software interface may refer to a wide range of different types of interfaceinterfaces at different "levels". For example, an operating system may interface with pieces of hardware. [[application software|Application]]s or [[Computer program|program]]s running on the operating system may need to interact via data [[Stream (computing)|streams]], filters, and pipelines.<ref name="BuyyaMastering13">{{cite book |url=https://books.google.com/books?id=VSDZAgAAQBAJ&pg=SA2-PA13 |title=Mastering Cloud Computing |author=Buyya, R. |publisher=Tata McGraw-Hill Education |page=2.13 |year=2013 |isbn=9781259029950}}</ref> In [[Object-oriented programming|object oriented programs]], objects within an application may need to interact via [[Method (computer science)|methods]].<ref name="PooObject08">{{cite book |chapter=Chapter 2: Object, Class, Message and Method |title=Object-Oriented Programming and Java |url=https://archive.org/details/springer_10.1007-978-1-84628-963-7 |author1=Poo, D. |author2=Kiong, D. |author3=Ashok, S. |publisher=Springer-Verlag |pages=7–15 |year=2008 |isbn=9781846289637}}</ref>

=== In practice ===

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=== In object-oriented languages ===

{{Main article|Interface (object-oriented programming)|Concept (generic programming)}}

In some [[Object-oriented programming|object-oriented]] languages, especially those without full [[multiple inheritance]], the term ''interface'' is used to define an [[Abstract data type|abstract type]] that acts as an [[abstraction]] of a [[Class (computer science)|class]]. It contains no data, but defines behaviours as [[Method (computer science)|method]] signatures. A [[Classclass (computer science)|class]] having code and data for all the methods corresponding to that interface and declaring so is said to ''implement'' that interface.<ref>{{cite web|url=http://docs.oracle.com/javase/tutorial/java/concepts/interface.html|title=What Is an Interface|work=The Java Tutorials|publisher=Oracle|access-date=2012-05-01|url-status=live|archive-url=https://web.archive.org/web/20120412093619/http://docs.oracle.com/javase/tutorial/java/concepts/interface.html|archive-date=2012-04-12}}</ref> Furthermore, even in single-inheritance-languages, one can implement multiple interfaces, and hence can ''be'' of different types at the same time.<ref>{{cite web|url=http://docs.oracle.com/javase/tutorial/java/IandI/createinterface.html|title=Interfaces|work=The Java Tutorials|publisher=Oracle|access-date=2012-05-01|url-status=live|archive-url=https://web.archive.org/web/20120526080117/http://docs.oracle.com/javase/tutorial/java/IandI/createinterface.html|archive-date=2012-05-26}}</ref>

An interface is thus a [[data type|type]] definition; anywhere an object can be exchanged (for example, in a [[function (computer science)|function]] or [[method (computer science)|method]] call) the ''type'' of the object to be exchanged can be defined in terms of one of its implemented ''interface''s or base-classes rather than specifying the specific [[Class (computer science)|class]]. This approach means that any class that implements that interface can be used.{{citation needed|date=June 2018}} For example, a [[Skeleton (computer programming)|dummy implementation]] may be used to allow development to progress before the final implementation is available. In another case, a [[Test-driven development#Fakes, mocks and integration tests|fake or mock]] implementation may be substituted during testing. Such [[Method stub|stub]] implementations are replaced by real code later in the development process.

Usually, a method defined in an interface contains no code and thus cannot itself be called; it must be implemented by non-abstract code to be run when it is invoked.{{citation needed|date=June 2018}} An interface called "<code>[[Stack (data structure)|Stack]]</code>" might define two methods: <code>push()</code> and <code>pop()</code>. It can be implemented in different ways, for example, <code>FastStack</code> and <code>GenericStack</code>—the first being fast, working with a data structure of fixed size, and the second using a data structure that can be resized, but at the cost of somewhat lower speed.

Though interfaces can contain many methods, they may contain only one or even none at all. For example, the [[Java (programming language)|Java]] language defines the interface {{Java|Readable}} that has the single {{Java|read()}} method; various implementations are used for different purposes, including {{Java|BufferedReader}}, {{Java|FileReader}}, {{Java|InputStreamReader}}, {{Java|PipedReader}}, and {{Java|StringReader}}. [[Marker interface pattern|Marker interfaces]] like {{Java|Serializable}} contain no methods at all and serve to provide run-time information to generic processing using [[Reflection (computer programming)|Reflection]].<ref>

{{cite web

|access-date = 2011-08-04

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* [[Business Interoperability Interface]]

* [[Computer bus]]

* [[Coupling (computer programming)]]

* [[Hard disk drive interface]]

* [[Implementation (computer science)]]