API abbreviates Application Program Interface and refers to a set of protocols, tools and routines for building software applications. The term specifies how components of software ought to interact and be utilized when programming components of graphical user interface (GUI). A desirable API eases the process of developing a program by availing all required building blocks, which are put together by a programmer.

Diverse kinds of APIs are available to suit operating systems, websites and various other applications. Windows for example has numerous API sets employed by system applications and hardware. API facilitates copy-pasting of text across different applications in this case. Windows also offers an API that enables programmers to write applications consistent with their operating conditions. In addition, APIs are website-specified, such as those which allow developers to apply existing infrastructure for creating web stores that are more specialized. Tertiary software developers equally utilize Web APIs for creating customized software solutions for end-users.

Importance of API in GUI Programming

Apart from accessing databases and computer hardware like video cards or hard disk drives, an API can ease the process of programming GUI components. An API can for instance facilitate the integration of new characteristics into existing applications, known as “plug-in API”. In addition, an API can aid otherwise distinct applications in the sharing of data, which assists in integrating and enhancing application functions.

Library Representation of API

Oftentimes, APIs are presented in form of library which includes specifications for object classes, data structures, routines and variables. In notable cases like REST and SOAP services, an API specifies remote calls that are exposed to API users. An API specification can come in diverse forms. This includes an International Standard like POSIX, programming language libraries such as Standard Template Library in Java API or C++ or even vendor documentation like Microsoft Windows API.

API Application in Procedural Languages

For the majority of procedural languages, API is used for specifying routines or functions which accomplish a particular task or can interact with a particular software component. Such specification gets presented in a format readable by humans in electronic formats such as man pages or eBooks or in paper books.

By example, math API utilized by Unix systems specifies on usage of the mathematical functions included within the math library. A function termed sqrt () lies among these and may be employed in computing square root of a specified number.

API Application in Object-Oriented Languages

An object API describes how things work within a particular object-oriented language. It is usually expressed as a class-set with an associated list comprising of class methods. In Java language for instance, a class scanner is required to import java.util.Scanner library if meant to be utilized, to facilitate usage of type Scanner objects by invoking certain class’ methods.

In general, an API in object-oriented languages normally includes description of a set of class definitions with a behaviour-set associated with such classes. The abstract concept is linked to real functionality either availed or exposed by classes implemented through class methods. There are many popular examples of APIs including those for Google Maps, YouTube, Amazon Product Advertising and Twitter.