struct MasterDirectoryBlock {
	UInt16 		drSigWord; 	volume signature
	UInt32 		drCrDate; 	date and time of volume creation
	UInt32 		drLsMod; 	date and time of last modification
	UInt16 		drAtrb; 	volume attributes
	UInt16 		drNmFls; 	number of files in root directory
	UInt16 		drVBMSt; 	first block of volume bitmap
	UInt16 		drAllocPtr; 	start of next allocation search
	UInt16 		drNmAlBlks; 	number of allocation blocks in volume
	UInt32 		drAlBlkSiz; 	size (in bytes) of allocation blocks
	UInt32 		drClpSiz; 	default clump size
	UInt16 		drAlBlSt; 	first allocation block in volume
	UInt32 		drNxtCNID; 	next unused catalog node ID
	UInt16 		drFreeBks; 	number of unused allocation blocks
	UInt8		drVNLength;	length of volume name
	Char   		drVN[28]; 	volume name
	UInt32 		drVolBkUp; 	date and time of last backup
	UInt16 		drVSeqNum; 	volume backup sequence number
	UInt32 		drWrCnt; 	volume write count
	UInt32 		drXTClpSiz; 	clump size for extents overflow file
	UInt32 		drCTClpSiz; 	clump size for catalog file
	UInt16 		drNmRtDirs; 	number of directories in root directory
	UInt32 		drFilCnt; 	number of files in volume
	UInt32 		drDirCnt; 	number of directories in volume
	HFSVolumeFinderInfo drFndrInfo; information used by the Finder
	UInt16 		drVCSize; 	size (in blocks) of volume cache
	UInt16 		drVBMCSize; 	size (in blocks) of volume bitmap cache
	UInt16 		drCtlCSize; 	size (in blocks) of common volume cache
	UInt32 		drXTFlSize; 	size of extents overflow file
	ExtDataRec 	drXTExtRec; 	extent record for extents overflow file
	UInt32 		drCTFlSize; 	size of catalog file
	ExtDataRec 	drCTExtRec; 	extent record for catalog file
};
