window_blank(_c)

	did_it.i4.v = window_blank(window_id.i2.r, row.i4.r, column.i4.r,
				   num_chars.i4.r [,color.i4.r])

	did_it.i4.v = window_blank_c(window_id.i2.v, row.i4.v, column.i4.v,
				     num_chars.i4.v [,color.i4.v])

	This routine will write blanks to the window indicated by "window_id".

	window_id	window ID (use WMNGR_BACKGROUND for background window)
	row, column	starting window coordinate location
	num_chars	number of blanks to write
	[color]		color of blanks (default is BLACK)
			(constants are in 'cnsparam')

	This function returns status values as follows:

	TRUE			window I/O actually done
	FALSE			no window I/O done

	This function requires the following include files:

	cnsparam_h, cbslib_h

	Related functions:

	window_erase_line(_c), window_erase_to_eol_c, window_erase_c,
	btvblnk(_c), intro_tv_windows

	C/C++ usage:

	short	window_id;
	int	did_it;
	int	row = 1;
	int	column = 1;
	int	num_chars = 0;
	int	color = BLACK;

	did_it = window_blank_c(window_id,row,column,num_chars,color);