num_chars.i4.v = wn_printf_at_c(x.r4.v, y.r4.v, format_string.i1a.r
					[,value_1, value_2, ...])

	This routine draws a formatted text string at virtual coordinates
	X,Y in a graphics window specified by a previous call to
	wn_active(_c).  wn_view(_c) and wn_world(_c) must also be
	called before calling this routine.  The color of the text is
	determined by the most recent call to wn_color(_c).

	x, y		real world coordinates of lower left hand
			corner of text string  (If text character scaling
			is selected with a call to wn_text_scaling_c,
			the following special coordinate values are supported.
			A value of WN_CENTER_IT for either coordinate will
			center the text relative to the active window for that
			plane.  A value of WN_JUSTIFY_MIN or WN_JUSTIFY_MAX
			will align the text to the minimum or maximum
			respectively of the corresponding axis.)
	format_string	null terminated string which contains the
			characters to be written literally or converted
			as specified by the optional value arguments
	[value_1...]	optional values which correspond to conversion
			expressions in the format string

	This function returns status values as follows:

	CBS_NOSETUP		an active window has not been established
	otherwise		number of characters output

	This function requires the following include files:

	cnsparam_h, cbslib_h

	Related functions:

	wn_text(_c), wn_color(_c), wn_text_size(_c), wn_text_rotation(_c),
	wn_text_attributes_c, wn_text_scaling_c, wn_display_value(_c),
	wn_blank_c, wn_external_text(_c), wn_colored_text_c,
	wn_external_colored_text_c, wn_external_display_value_c,
	wn_read_text_format, wn_set_background_format_c,
	wn_read_background_format, wn_flush, intro_graphics_windows

	C/C++ usage:

	static const char	format_string[] = "This is a formatted string for %F.";
	int	num_chars;
	float	x = 1.0;
	float	y = 1.0;

	num_chars = wn_printf_at_c(x,y,format_string,CNV_DEVICE,27235);