file_id

IN:

File identifier returned by Hopen

	Purpose	Initializes the GR interface.
	Return value	Returns the GR interface identifier if successful and FAIL (or -1) otherwise.
	Description	GRstart initializes the GR interface for the file specified by the parameter file_id.
		This routine is used with the GRend routine to define the extent of the GR interface session. As with the start routines in the other interfaces, GRstart initializes the internal interface structures needed for the remaining GR routines. Use the general purpose routines Hopen and Hclose to manage file access. The GR routines will not open and close HDF files.

	FORTRAN	integer function mgstart(file_id)
		integer file_id