status.i4.v = window_tvsave_c(window_id.i2.v, row.i4.v, column.i4.v,
				      num_rows.i4.v, num_columns.i4.v, vun.i2.v,
				      record_number.i4.v [,record_size.i4.v])

	This routine will read a rectangular block from a window, compress it,
	and store it in a Filesharing record.  The compression method usually
	gives savings of more than 50% compared with a raw array of XCHAR
	structures.  Even relatively dense 48 by 120 images will fit into a
	3930 byte Filesharing record.  Only changes of color code are stored.
	Blink codes are not stored. Repeated characters are stored as a repeat
	count and the character code. In order to limit the number of color
	codes stored, the foreground color of blank characters may be changed
	to be the same as that of the previous character.  A compressed image
	can be displayed using the window_tvdisp(_c) routine.

	window_id	window ID (use WMNGR_BACKGROUND for background window)
	row, column	upper left hand corner of region to save
	num_rows	number of rows to save
	num_columns	number of columns to save
	vun		virtual unit number of the Filesharing file into which 
			the compressed image will be written.  The calling
			program must have previously opened this file for
			write access.  A small speed advantage can be had on
			subsequent displays if the file has relative
			organization and variable length records.
	record_number	record into which the compressed image will be written
	[record_size]	record size in bytes (default is 2048) (maximum is 3930)

	This function returns ACNET status values as follows:

	OK			success
	CBS_INVARG		parameter error (arguments out of range)
	CBS_NO_WINDOW		requested window does not exist
	CBS_INVSIZ		image is too large
	FSHARE_xxx		error writing image

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	window_tvdisp(_c), window_read_color_text_c, chkcmp

	C/C++ usage:

	static const char	file_name[] = "filename.txt";
	short	vun;
	short	window_id;
	int	open_status;
	int	access_mode = FMNGR_DIRECT;
	int	write_access = FMNGR_READ_ACCESS;
	int	retry = TRUE;
	int	ext_status;
	int	asynchronous = FALSE;
	int	max_record = FSHR_DEFAULT_MAX_RECORD;
	int	status;
	int	row = 1;
	int	column = 1;
	int	num_rows = WINDOW_HEIGHT;
	int	num_columns = WINDOW_WIDTH;
	int	record_number = 1;
	int	record_size = 2048;

	open_status = fm_open_c(&vun,file_name,access_mode,write_access,

	if (open_status == OK)
	status = window_tvsave_c(window_id,row,column,num_rows,num_columns,