INITIALIZATION.
This event keyword defines an event block whose event is triggered by the ABAP runtime environment during the flow of an executable program, directly after LOAD-OF-PROGRAM and before the selection screen processing of any existing standard selection screen. This gives you the one-time opportunity to initialize the input fields of the selection screen, including those defined in the logical database linked with the program.
When an executable program defines a standard selection screen, it is called again by the ABAP runtime
environment after execution, which triggers the INITIALIZATION
event again. In this case, initializing parameters or selection criteria of the selection screen has no effect, because they are automatically supplied with the preceding user inputs from the selection screen during the
selection screen event
AT SELECTION-SCREEN OUTPUT. To explicitly initialize the selection screen for each call, you must use the event AT SELECTION-SCREEN OUTPUT.
Refer to the example for reporting events.