filename	IN:	Name of the file
	tag	IN:	Tag of the data object assigned the description
	ref	IN:	Reference number of the data object assigned the description
	desc_buf	OUT:	Buffer allocated to hold the description
	buf_len	IN:	Size of the buffer allocated to hold the description

	Purpose	Reads the description assigned to the data object with the given tag and reference number.
	Return value	Returns SUCCEED (or 0) if successful and FAIL (or -1) otherwise.
	Description	The parameter buf_len specifies the storage space available for the description. The length of buf_len must account for the null termination character appended to the description.

	FORTRAN	integer function dagdesc(filename, tag, ref, desc_buf, buf_len)
		character*(*) filename, desc_buf
		integer tag, ref
		integer buf_len