A set of routines, protocols and tools referred to as "building blocks" used in business application software development(A good API makes it easier to develop a program by providing all the building blocks related to functional characteristics of an operating system that applications need to specify, for example, when interfacing with the operating system (e.g., provided by Microsoft Windows, different versions of UNIX). A programmer utilizes these APIs in developing applications that can operate effectively and efficiently on the platform chosen)
Application Program Interface(A set of routines that an application uses to request and carry out lower-level services performed by a computer's operating system. These routines usually carry out maintenance tasks such as managing files and displaying information)
