DOS Drive Info Block (DDIB)

        51h bytes per drive (58h bytes for DOS 4.0), starting with A: ...


        Offset Size   Contens
        ------------------------------------------------------------------
        00-43  Bytes  Current path as ASCIIZ, starting with 'x:\'
        44     Byte   Drive-flags
                        11xx xxxx  00: Not a valid entry
                                   01: Physical drive
                                   10: Network drive
                                   11: Invalid
                        xx1x xxxx  1=Drive is JOIN'ed
                        xxx1 xxxx  1=Subst drive
        45-48  DWord  Pointer to DOS Drive Parameter Block (DDPB) for
                      this drive
        49-4A  Word   Starting cluster of current dir? FFFFh if never
                      accessed.
        4B-4E         Unknown (-1 always)
        4F-50  Word   Minimal path len. Used by subst (always 2 if drive
                      isn't substituted). Example:
                         SUBST D: C:\          (2)
                         SUBST E: C:\ARC       (6)
                         SUBST F: C:\ARC\TEST  (11)


        Note: In DOS 4.0, the DDIB contains 7 additional bytes, which
              always is zero (at on my machine ...)