I have two questions:
1. Can the selection screen generated by an executable program/report, be modified in Screen painter? If yes, then how?
2. ABAP must be generating some code (apart from Flow logic) for the layout designed in Screen Painter. Can this be read and from where?
The selection screen can be modified. However, should the screen ever be generated again, you will lose your changes. So it is not worth doing. The generation of the selection screen is entirely controlled by the ABAP commands in the program. RSDBRUNT <REPINI> and <SYSINI> contain most of the code. You can find this by entering into system debugging, /hs.
This was first published in August 2002