- basically consists of a variety of functions or procedures that an application program
can call upon, as well as data structures, constants, and
various definitions needed to describe system resources.
- Applications programs use the API by including calls to routines in a program library
- For example, this simple function puts a message box on the screen:
MessageBox (0, “Program Initialization Failed!”,
“Error!”, MB_ICONEXCLAMATION | MB_OK | MB_
SYSTEMMODAL);
- API for a major operating system such as Windows contains hundreds of functions, data structures,and definitions.
- In order to simplify learning to access the
necessary functions and to promote the writing of readable
code, compiler developers such as microsoft and Borland
have devised frameworks of C++ classes that package related
functions together.