application program interface
[‚ap·lə¦kā·shən ¦prō·grəm ′in·tər‚fās] (computer science)
A language that enables communication between computer programs, in particular between application programs and control programs. Abbreviated API.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
Application Program Interface
(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.
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.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)
API
(Application Programming Interface) A language and message format used by an application program to communicate with the operating system or some other control program such as a database management system (DBMS) or communications protocol. APIs are implemented by writing function calls in the program, which provide the linkage to the required subroutine for execution. Thus, an API implies that a driver or program module is available in the computer to perform the operation or that software must be linked into the existing program to perform the tasks.Plenty of API Programming Is Done
Understanding APIs is a major part of what a programmer does. Except for writing the business logic that performs the actual data processing, all the rest of the programming is writing the code to communicate with the operating system.
APIs can be daunting, especially the calls to the user interface to display the menus, buttons and windows on screen. There are more than a thousand API calls in a major operating system such as Windows, macOS or Linux. However, although APIs have counterparts in each OS to invoke identical operations, the actual syntax and coding may vary significantly between platforms. See integrated development environment, function and interface.
APIs Become Obsolete
Operating system vendors upgrade their capabilities all the time with new functions in the latest version. However, after many years, in order to streamline their software, vendors discontinue support for older routines. The old APIs no longer work when run in the newer version of the OS, which means the app fails to operate.
Business organizations can put off installing the latest OS for a while to keep their existing apps running. However, commercial developers may have little choice because they need to be compatible with the OS versions in use. In addition, they might be denied access to the vendor's online store if their apps are not current.
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