What is Application Programming Interface (API)?
An application programming interface (API) is bassically a set of routines, data structures, object classes and/or protocols provided by libraries and/or operating system services in order to support the building of applications. Its is a formalized set of software calls and routines that can be referenced by an application program in order to access supporting system or network services. API may be :
> Language-dependent : Its only available in a particular programming language, utilizing the particular syntax and elements of the programming language to make the API convenient to use in this particular context.
> Language-independent : It is written in a way that means they can be called from several programming languages which is typically an assembly/C-level interface. This is a desired feature for a service-style API which is not bound to a particular process or system and is available as a remote procedure call.