DOS Fn 53H: Convert BPB to DPB

                                                Compatibility: 2.0+? ◄undoc► 
 Expects: AH    53H
          DS:BX addr of a BIOS Parameter Block (as used by device drivers)
          ES:BP addr of buffer to receive a Drive Parameter Block (DPB)
          ──────────────────────────────────────────────────────────────────
 Returns: ES:BX buffer contains a filled-in DPB
          ──────────────────────────────────────────────────────────────────
    Info: This undocumented function is used by DOS during startup to
          prepare its chain of DPBs.

          DOS issues a DvRq 02H (Build BPB) request to a device driver and
          then calls this to put the data into a more useful form.  It then
          installs the DPB into a chain of DPBs (see DosVarsRec).

          It has no practical use for application programs, but it might be
          used by a disk utility or a block device driver which installs
          itself from the DOS command line.

See Also: Device Drivers
          Disk Drive Functions
                                    -♦-