file_id	IN:	File identifier returned by Hopen
	tag	IN:	Tag to be counted

	Purpose	Returns the number of instances of a tag in a file.
	Return value	Returns the number of instances of a tag in a file if successful, and FAIL (or -1) otherwise.
	Description	Hnumber determines how many objects with the specified tag are in a file. To determine the total number of objects in a file, set the tag argument to DFTAG_WILDCARD. Note that a return value of zero is not a fail condition.

	FORTRAN	integer function hnumber(file_id, tag)
		integer file_id, tag