In order to organize the dialog flow in your application,
you must link the objects of the user interface with functions of the DataView
programming interface at the moment of user actions. For this purpose, events,
items, buttons, and masks provide different triggers at which you can call userexits.
Userexits are task-oriented program routines. for repeating standard tasks DataView
provides such userexit's in a standard userexit library. In order to install
special application-specific functionality, you can program your own C-userexits.