filename	IN:	Name of the file
	tag	IN:	Tag of the data object to be assigned the description
	ref	IN:	Reference number the data object to be assigned the description
	description	IN:	Sequence of ASCII characters (may include NULL or '\0')
	desc_len	IN:	Length of the description

	Purpose	Writes a description for 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 description can contain any sequence of ASCII characters; it does not have to be a string. If DFANputdesc is called more than once for the same tag/reference number pair, only the last description is stored in the file.

	FORTRAN	integer function dapdesc(filename, tag, ref, description, desc_len)
		character*(*) filename, description
		integer tag, ref, desc_len