SCREEN [(#ch)] (FN Toolkit only)
The visible screen on a standard QL is actually 32K of memory. The start address of the screen is normally 131072, but can change on Minerva and higher resolution implementations of the QL, so the start address should be determined before accessing the screen directly. The function SCREEN returns that start address.
The FN Toolkit version allows you to specify a channel - if the channel is specified, then the start address for the screen on which that channel is open is returned. This is mainly only of use to Minerva and Amiga QDOS users who can have windows open on either the Default Screen or the Other Screen (provided their dual screen mode is active). Thus SCREEN(#3) can be used to find the start address of the second screen if that is where #3 is located.