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struc DeviceParams              ; Device parameters for medium
 dpSpecFunc             db ?    ; Special functions
 dpDevType              db ?    ; Device type
 dpDevAttr              dw ?    ; Device attributes
 dpCylinders            dw ?    ; Max. no. of cylinders (set by device)
 dpMediaType            db ?    ; Medium currently accepted by drive
                               ;; Start of BIOS parameter block (BPB)
 dpBytesPerSec          dw ?    ; No. of bytes per sector
 dpSecPerClust          db ?    ; No. of sectors per cluster
 dpResSectors           dw ?    ; No. of reserved sectors
 dpFATs                 db ?    ; No. of file allocation tables
 dpRootDirEnts          dw ?    ; No. of root-directory entries
 dpSectors              dw ?    ; Total no. of sectors (0 if > 32 MB)
 dpMedia                db ?    ; Media descriptor
 dpFATsecs              dw ?    ; No. of sectors per FAT
 dpSecPerTrack          dw ?    ; Sectors per track
 dpHeads                dw ?    ; No. of heads
 dpHiddenSecs           dd ?    ; No. of hidden sectors
 dpHugeSectors          dd ?    ; No. of sectors if dpSectors = 0
                               ;; End of BIOS parameter block (BPB)
ends

;       ; dpSpecFunc (Int 21h 440Dh /40h)
;       Bit   Meaning
;       0     0 = Use dpBytesPerSec through dpHugeSectors to set the
;                 default BPB for this device.
;             1 = Use the device BPB for all subsequent Build BPB
;                 requests.
;       1     0 = Read all fields.
;             1 = Ignore all fields, but read the TrackLayout
;                 structure appended to the end of this structure.
;       2     0 = Do not use.
;             1 = The sectors in the track are all the same size,
;                 and the sector numbers are in the range 1 through
;                 the total number of sectors on the track. This bit
;                 should always be set.
;       3-7   Reserved (must be zero).
;
;
;       ; dpDevType
;       00h = 320/360K
;       01h = 1.2 MB
;       02h = 720K
;       03h = 8-inch, single-density
;       04h = 8-inch, double-density
;       05h = Hard disk
;       06h = Tape drive
;       07h = 1.44 MB
;       08h = Read/write optical
;       09h = 2.88 MB
;
;
;       ; dpDevAttr
;       Bit   Meaning
;       0     0|1 = The medium is|isn't removable.
;       1     0|1 = Disk change-line isn't|is supported
;                   (hasn't|has door-lock support).
;       2-15  Reserved (must be zero).
;
;
;       ; dpMediaType
;       Specifies which medium the drive currently accepts (for drives
;       that accept more than one media type). For a 1.2 MB drive, if
;       bit 0 is clear, it indicates, that the drive accepts
;       quad-density, 1.2 MB disks (the default media type); if bit 0
;       is set, the drive accepts double-density, 320/360K disks.
;
;
;       ; dpSecPerClust
;       Specifies the number of sectors in a cluster. The sectors must
;       be consecutive, and the number must be a power of 2.
;
;
;       ; dpResSectors
;       Specifies the number of reserved sectors on the drive,
;       beginning with sector 0. Typically, this value is 1 (for the
;       startup sector), unless the disk-drive manufacturer's software
;       reserves additional sectors.
;
;
;       ; dpFATs
;       Specifies the number of file allocation tables (FATs)
;       following the reserved sectors. Most versions of DOS maintain
;       one or more copies of the primary FAT and use the extra copies
;       to recover data on the disk if the first FAT is corrupted.