uses the address of window structures to identify windows internally. It also uses these addresses as window identifiers in the overlay functions. The ``get identifier of the next window'' (ax=22) function is used to look through the windows. You pass the function a window identifier, and it passes back the identifier of the next window. If you pass in a 0, it passes back the identifier of the top window. If you get back a 0, then you passed in the identifier of the bottom window.
The ``get selection information'' function (ax=12) will give you the window identifier of the selection window, and the ``set selection information'' function (ax=13) will set the selection window. The ``set active window'' function (ax=5) will change the active window.
Once you have a window identifier you can get information about it with the ``get window location'' (ax=15) and ``get window information'' (ax=16) functions.