An application programming interface is a collection of functions, routines, procedures, protocols, and resources that can be used for building software. In other words, an application programming interface—API for short—is a collection of well-defined and appropriately structured methods or channels of communication between software components.
Application programming interfaces can be developed for use with various application domains. Some common application domains that APIs are developed for include the development of web-based systems, operating systems, and computer hardware, as well as interaction with embedded systems.
