Instance (computer science)

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title: "Instance (computer science)" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["object-(computer-science)"] description: "Concrete manifestation of an object (class) in software development" topic_path: "technology/computing" source: "https://en.wikipedia.org/wiki/Instance_(computer_science)" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Concrete manifestation of an object (class) in software development ::

In computer science, an instance or token (from metalogic and metamathematics) is an occurrence of a software element that is based on a type definition. cite report |last1=Dahl |first1=Ole-Johan |author-link=Ole-Johan Dahl |last2=Myhrhaug |first2=Bjørn |last3=Nygaard |first3=Kristen |author3-link=Kristen Nygaard |date=1970 |url=http://www.edelweb.fr/Simula/#7 |title=Common Base Language |publisher=Norwegian Computing Center |access-date=20 August 2025 |url-status=usurped |archive-url=https://web.archive.org/web/20240919044713/https://www.softwarepreservation.org/projects/ALGOL/manual/Simula-CommonBaseLanguage.pdf |archive-date=2024-09-19 When created, an occurrence is said to have been instantiated, and both the creation process and the result of creation are called instantiation.

Examples

; Class instance: An object-oriented programming (OOP) object created from a class. Each instance of a class shares a data layout but has its own memory allocation.

; Procedural instance: Although isn't common the use of this concept in computer science each procedure call also was considered an "instance" of the procedure in Simula.

; Computer instance: An occurrence of a virtual machine which typically includes storage, a virtual CPU.

; Polygonal model: In computer graphics, it can be instantiated in order to be drawn several times in different locations in a scene which can improve the performance of rendering since a portion of the work needed to display each instance is reused.

; Program instance: In a POSIX-oriented operating system, it refers to an executing process. It is instantiated for a program via system calls such as fork() and exec(). Each executing process is an instance of a program which it has been instantiated from.

References

References

1. Bach, Maurice J.. (1986). ["The Design of the UNIX Operating System"]({{Google books). Prentice Hall.

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