Format of a TDirectory record in release 6.22.06. It is never compressed.

If the SeekKeys or SeekPdir in the TKey are located past the 32 bit file limit (> 2000000000), then these fields will be 8 instead of 4 bytes and 1000 is added to the TKey Version.

If the SeekDir, SeekParent, or SeekKeys in the TDirectory header are past the 32 bit file limit, then these fields will be 8 instead of 4 bytes and 1000 is added to the TDirectory Version.

 ----------TKey--------------
  byte 0->3           Nbytes    = Number of bytes in compressed record (Tkey+data)              TKey::fNbytes
       4->5           Version   = TKey class version identifier                                 TKey::fVersion
       6->9           ObjLen    = Number of bytes of uncompressed data                          TKey::fObjLen
      10->13          Datime    = Date and time when record was written to file                 TKey::fDatime
                                | (year-1995)<<26|month<<22|day<<17|hour<<12|minute<<6|second
      14->15          KeyLen    = Number of bytes in key structure (TKey)                       TKey::fKeyLen
      16->17          Cycle     = Cycle of key                                                  TKey::fCycle
      18->21 [18->25] SeekKey   = Byte offset of record itself (consistency check)              TKey::fSeekKey
      22->25 [26->33] SeekPdir  = Byte offset of parent directory record                        TKey::fSeekPdir
      26->26 [33->33] lname     = Number of bytes in the class name (10)                        TKey::fClassName
      27->.. [34->..] ClassName = Object Class Name ("TDirectory")                              TKey::fClassName
       0->0           lname     = Number of bytes in the object name                            TNamed::fName
       1->..          Name      = lName bytes with the name of the object `<directory-name>`    TNamed::fName
       0->0           lTitle    = Number of bytes in the object title                           TNamed::fTitle
       1->..          Title     = lTitle bytes with the title of the object `<directory-title>` TNamed::fTitle
 --------DATA----------------
       0->1           Version   = TDirectory class version identifier                           TDirectory::Class_Version()
       2->5           DatimeC   = Date and time when directory was created                      TDirectory::fDatimeC
                                | (year-1995)<<26|month<<22|day<<17|hour<<12|minute<<6|second
       6->9           DatimeM   = Date and time when directory was last modified                TDirectory::fDatimeM
                                | (year-1995)<<26|month<<22|day<<17|hour<<12|minute<<6|second
      10->13          NbytesKeys= Number of bytes in the associated KeysList record             TDirectory::fNbyteskeys
      14->17          NbytesName= Number of bytes in TKey+TNamed at creation                    TDirectory::fNbytesName
      18->21 [18->25] SeekDir   = Byte offset of directory record in file                       TDirectory::fSeekDir
      22->25 [26->33] SeekParent= Byte offset of parent directory record in file                TDirectory::fSeekParent
      26->29 [34->41] SeekKeys  = Byte offset of associated KeysList record in file             TDirectory::fSeekKeys
      30->31 [42->43] UUID vers = TUUID class version identifier                                TUUID::Class_Version()
      32->47 [44->59] UUID      = Universally Unique Identifier                                 TUUID::fTimeLow through fNode[6]
      48->59          Extra space to allow SeekKeys to become 64 bit without moving this header

Format of a TDirectory record in release 3.02.06. It is never compressed.

 ----------TKey--------------
  byte 0->3  Nbytes    = Number of bytes in compressed record (Tkey+data)              TKey::fNbytes
       4->5  Version   = TKey class version identifier                                 TKey::fVersion
       6->9  ObjLen    = Number of bytes of uncompressed data                          TKey::fObjLen
      10->13 Datime    = Date and time when record was written to file                 TKey::fDatime
                       | (year-1995)<<26|month<<22|day<<17|hour<<12|minute<<6|second
      14->15 KeyLen    = Number of bytes in key structure (TKey)                       TKey::fKeyLen
      16->17 Cycle     = Cycle of key                                                  TKey::fCycle
      18->21 SeekKey   = Byte offset of record itself (consistency check)              TKey::fSeekKey
      22->25 SeekPdir  = Byte offset of parent directory record                        TKey::fSeekPdir
      26->26 lname     = Number of bytes in the class name (10)                        TKey::fClassName
      27->.. ClassName = Object Class Name ("TDirectory")                              TKey::fClassName
       0->0  lname     = Number of bytes in the object name                            TNamed::fName
       1->.. Name      = lName bytes with the name of the object `<directory-name>`    TNamed::fName
       0->0  lTitle    = Number of bytes in the object title                           TNamed::fTitle
       1->.. Title     = lTitle bytes with the title of the object `<directory-title>` TNamed::fTitle
 --------DATA----------------
       0->0  Modified  = True if directory has been modified                           TDirectory::fModified
       1->1  Writable = True if directory is writable                                  TDirectory::fWriteable
       2->5  DatimeC   = Date and time when directory was created                      TDirectory::fDatimeC
                       | (year-1995)<<26|month<<22|day<<17|hour<<12|minute<<6|second
       6->9  DatimeM   = Date and time when directory was last modified                TDirectory::fDatimeM
                       | (year-1995)<<26|month<<22|day<<17|hour<<12|minute<<6|second
      10->13 NbytesKeys= Number of bytes in the associated KeysList record             TDirectory::fNbyteskeys
      14->17 NbytesName= Number of bytes in TKey+TNamed at creation                    TDirectory::fNbytesName
      18->21 SeekDir   = Byte offset of directory record in file                       TDirectory::fSeekDir
      22->25 SeekParent= Byte offset of parent directory record in file                TDirectory::fSeekParent
      26->29 SeekKeys  = Byte offset of associated KeysList record in file             TDirectory::fSeekKeys