API is an acronym that denotes Application Control Interface. API is also commonly called application programming interface. An API is a set of routines, protocols, and tools that are used for building software applications. In other words, an API provides the building blocks for a programmer to build the application software. An API contains the data and control information that enables a higher-level application program to make use of the lower-level services and functions of another application, operating system, or driver. In systems offered by vendors, the API is the public interface between the programming code and the program function.

There may be many APIs programmed into an operating system, each of which allows the user to perform a different function. In a sense, the APIs allow a user to narrow his or her request to the level of specificity that is...