API (Application Programming Interface) is the list or stack of subprograms, classes, procedures, constants, and functions provided by the application and can be used by developers for creating their applications or libraries in external software.

 

API detects functionality provided by a program, wherein it is not important for a programmer how this functionality is implemented. Thus, API is a "black box", but in a good way. A programmer who creates the plugin does not need to know how this or that procedure is implemented in the program itself. He needs only those function parameters and the result it returns.

 

The plugin applications created based on these systems calls are strictly described in API documentation.