occluded.i4.v = wn_occluded_c(window_id.i4.v)

	This routine returns a value of TRUE if the graphical window
	indicated is (partially or completely) occluded.  If a nonexistent
	window is requested, a value of TRUE is returned.

	window_id	window ID (use WN_BACKGROUND for background window)

	This function returns status values as follows:

	TRUE			window is occluded
	FALSE			window is exposed

	This function requires the following include files:

	cnsparam_h, cbslib_h

	Related functions:

	wn_intersect_c, intro_graphics_windows

	C/C++ usage:

	int	occluded;
	int	window_id;

	status = wn_occluded_c(window_id);