window_tvm(_c)

	did_it.i4.v = window_tvm(window_id.i2.r, row.i4.r, column.i4.r,
				 text.i1a.r, num_chars.i4.r [,color.i4.r])

	did_it.i4.v = window_tvm_c(window_id.i2.v, row.i4.v, column.i4.v,
				   text.i1a.r, num_chars.i4.v [,color.i4.v])

	This routine will display text in the window indicated by "window_id"
	if "num_chars" is greater than or equal to zero.  It will read in
	text if "num_chars" is less than zero.  This routine will return
	a value of TRUE if any characters are actually read or written.
	Otherwise, it will return a value of FALSE.  Characters can only
	be read from the visible portion of the window with this routine.

	window_id	window ID (use WMNGR_BACKGROUND for background window)
	row, column	starting window coordinate location
			(1,1 is the location inside the upper left hand
			 corner of a bordered window or 0,0 for a borderless
			 window)
	text		user buffer of ASCII data to be read or written,
			one character per byte
	num_chars	number of ASCII characters to be read from or
			written to the screen.  If the value of "num_chars"
			is negative, a read operation is performed.  (Note :
			A null string will be returned if the window is
			occluded.)  If "num_chars" is positive, a write
			operation is performed.  If "num_chars" is 0, the
			length of the string pointed to by "text" is
			determined and used.
	[color]		display color  (If a background color other than
			black is desired, a compound color value can be
			constructed using tv_colors or TV_COLORS_WBLINK.)
			(Note: This argument is optional and is ignored during
			 a read operation.) (default is WHITE)
			(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, extchrset_h

	Related functions:

	window_tvmx(_c), btvm(_c), btvmx(_c), window_draw_char_c,
	window_entry_to_row_c, window_display_value(_c),
	window_write_line_c, window_write_scroll_c, window_center_text(_c),
	window_vertical_text(_c), window_justify_text_c, window_write_string_c,
	window_up_case_c, window_down_case_c, window_text_fill(_c),
	window_read_text_c, window_input_value(_c), window_construct(_c),
	tv_colors, TV_COLORS_WBLINK, intro_tv_windows

	C/C++ usage:

	static const char	text[] = "Text";
	short	window_id;
	int	did_it;
	int	row = 1;
	int	column = 1;
	int	num_chars = 0;
	int	color = WHITE;

	did_it = window_tvm_c(window_id,row,column,text,num_chars,color);