is_exposed.i4.v = window_hole_c(window_id.i2.v, row.i4.v, column.i4.v)

	This routine returns a value of FALSE if the requested character
	location in the window indicated by "window_id" is occluded by
	another window.

	window_id	window ID (use WMNGR_BACKGROUND for background window)
	row, column	character position in full screen coordinates

	This function returns status values as follows:

	CBS_NO_WINDOW		requested window does not exist
	TRUE			location is exposed
	FALSE			location is occluded

	This function requires the following include files:

	cnsparam_h, cbslib_h, acnet_errors_h

	Related functions:

	window_gap_c, window_gap_length_c, window_exposed_region_c,
	screen_row(_c), screen_column(_c), intro_tv_windows

	C/C++ usage:

	short	window_id;
	int	is_exposed;
	int	row = 1;
	int	column = 1;

	row = screen_row_c(window_id,row);
	column = screen_column_c(window_id,column);

	is_exposed = window_hole_c(window_id,row,column);