This event keyword defines an event block for initializing an executable program. The associated event is triggered by the
ABAP runtime environment during the
flow of an
executable program, directly after
LOAD-OF-PROGRAM and before the
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
AT SELECTION-SCREEN OUTPUT. To explicitly initialize the selection screen for each call, you must use the event
AT SELECTION-SCREEN OUTPUT.