View source for Object (computer science)

{{Short description|Semantic instance with state, behavior, and identity}}

In [[software development]], an '''object''' is an [[entity]] semantic that has [[State (computer science)|state]], [[behavior]], and [[Identity (object-oriented programming)|identity]].
<ref name="ooa">{{cite book|title=Object-Oriented Analysis and Design with Applications |edition=3 |date=April 30, 2007 |author1=Grady Booch |author2=Robert Maksimchuk |author3=Michael Engle |author4=Bobbi Young |author5=Jim Conallen |author6=Kelli Houston |isbn=978-0201895513 |publisher= Addison-Wesley Professional}}</ref><ref name="Why Natural Scientists Should Care
About Object-Oriented Technology">http://www.literateprogramming.com/quantumoo.pdf</ref><ref name='Distributed Object-Based Programming Systems">https://dl.acm.org/doi/pdf/10.1145/103162.103165</ref><ref>https://dl.acm.org/doi/pdf/10.1145/38807.38823</ref>
An object can [[model]] some part of [[reality]] or can be an [[invention]] of the [[design process]] whose collaborations with other such objects serve as the mechanisms that provide some higher-level behavior. Put another way, an object represents an individual, identifiable item, unit, or entity, either real or abstract, with a well-defined role in the problem domain.<ref name="ooa"></ref>{{rp|76}}

A [[programming language]] can be classified based on its support for objects. A language that provides an encapsulation construct for state, behavior, and identity is classified as [[object-based language|object-based]]. If the language also provides [[polymorphism (computer science)|polymorphism]] and [[inheritance (object-oriented programming)|inheritance]] it is classified as [[Object-oriented programming|object-oriented]].<ref>https://www.eng.uwo.ca/electrical/faculty/capretz_l/docs/publications/ACM-SIGSOFT-v2.pdf</ref>{{Dubious|reason=this contradicts the highest article about OOP|date=November 2025}} A language that supports creating an object from a [[class (computer science)|class]] is classified as [[class-based programming|class-based]]. A language that supports object creation via a template object is classified as [[prototype-based programming|prototype-based]].

The concept of object is used in many different software contexts, including:

* Possibly the most common use is [[Computer memory|in-memory]] objects in a [[computer program]] written in an object-based language.

* [[Information systems]] can be [[object-oriented analysis and design|modeled]] with objects representing their components and interfaces.<ref name="ooa"/>{{rp|39}}
 
* In the [[relational model]] of [[database]] management, aspects such as [[Table (database)|table]] and [[Column (database)|column]] may act as objects.<ref name=Oppel>{{cite book |first=Andy |last=Oppel |title=SQL Demystified |publisher=McGraw Hill |year=2005| page=7 |isbn=0-07-226224-9}}</ref>

* [[Distributed object|Objects]] of a [[distributed computing]] system tend to be larger grained, longer lasting, and more service-oriented than programming objects.

In purely object-oriented programming languages, such as [[Java]] and [[C Sharp (programming language)|C#]], all classes might be part of an inheritance tree such that the root class is <code>Object</code>, meaning all objects instances of <code>Object</code> or implicitly extend <code>Object</code>.

==See also==
{{Columns-list|colwidth=22em|
<!--♦♦♦ Please keep the list in alphabetical order ♦♦♦-->

* [[Attribute (object-oriented programming)]]
* [[Business object]]
* [[Class (programming)|Class (computer programming)]]
* [[Class-based programming]]
* [[Data transfer object]]
* [[Declaration (computer programming)]]
* [[Distributed object]]
* [[Instance (computer science)]]
* [[Metaobject]]
* [[Method (computer programming)]]
* [[Object-capability model]]
* [[Object composition]]
* [[Object copying]]
* [[Object lifetime]]
* [[Object-based language]]
* [[Object-oriented programming]]
* [[Pointer (computer programming)]]
* [[Reference (computer science)]]
* [[Semantics (logic)]]
* [[Value object]]

}}

==References==
{{Reflist}}

==External links==
*[http://java.sun.com/docs/books/tutorial/java/concepts/object.html ''What Is an Object?''] from ''The Java Tutorials''

{{Software engineering}}
{{Data types}}
{{Authority control}}

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[[Category:Object (computer science)| ]]
[[Category:Data types]]
[[Category:Composite data types]]