an example can be found on AMOSPro_Examples:Examples/H-3/Help_39.AMOS
This comes in two flavours:
Selects a SCREEN for all future graphics and text operations, even if the screen is hidden away in the background.
Returns the number of the current screen you are using for your text and graphics operations.
an example can be found on AMOSPro_Examples:Examples/H-4/Help_40.AMOS