software interface application programming interface http://en.wikipedia.org/wiki/Application_programming_interface, accessed 25 November 2014. An application programming interface is a set of routines, protocols, and tools for building software applications. An API expresses a software component in terms of its operations, inputs, outputs, and underlying types. An API defines functionalities that are independent of their respective implementations, which allows definitions and implementations to vary without compromising each other. The API specifies how software components should interact. API