Selection screens are special screens that are defined with the help of ABAP statements.
The ABAP runtime environment fully controls the processing flow of selection screens.
To modify the selection screen before it is called (PBO) and react to user actions on the selection screen (PAI), the ABAP runtime environment generates a number of special selection screen events before the selection screen is displayed and after the user has executed actions on the selection screen
The basic form of the selection screen events is the AT SELECTION-SCREEN event. This event occurs after the runtime environment has passed all input data from the selection screen to the ABAP program. The other selection screen events allow programmers to modify the selection screen before it is sent and specifically check user input. Selection screen events occur both during standard and user-defined selection screen processing.
The SY-DYNNR system field contains the number of the active selection screen and helps to determine which selection screen is currently being processed in the event blocks.
Wikis with label "selection-screen"