Application Program Interface

part of the operating system which supplies applications with a uniform user interface, API

An application programming interface (API) is a source code interface that an operating system or library provides to support requests for services to be made of it by computer programs.
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A formalized set of software calls and routines that can be referenced by an application program in order to access supporting network services.

<programming> (API, or "application programming interface") The interface (calling conventions) by which an application program accesses operating system and other services. An API is defined at source code level and provides a level of abstraction between the application and the kernel (or other privileged utilities) to ensure the portability of the code.
An API can also provide an interface between a high level language and lower level utilities and services which were written without consideration for the calling conventions supported by compiled languages. In this case, the API's main task may be the translation of parameter lists from one format to another and the interpretation of call-by-value and call-by-reference arguments in one or both directions.
(1995-02-15)