BIOS Parameter Block (BPB).

typedef struct _BIOSPARAMETERBLOCK {
  USHORT     usBytesPerSector;                 /*  Number of bytes per sector. */
  BYTE       bSectorsPerCluster;               /*  Number of sectors per cluster. */
  USHORT     usReservedSectors;                /*  Number of reserved sectors. */
  BYTE       cFATs;                            /*  Number of FATs. */
  USHORT     cRootEntries;                     /*  Number of root directory entries. */
  USHORT     cSectors;                         /*  Number of sectors. */
  BYTE       bMedia;                           /*  Media descriptor. */
  USHORT     usSectorsPerFAT;                  /*  Number of secctors per FAT. */
  USHORT     usSectorsPerTrack;                /*  Number of sectors per track. */
  USHORT     cHeads;                           /*  Number of heads. */
  ULONG      cHiddenSectors;                   /*  Number of hidden sectors. */
  ULONG      cLargeSectors;                    /*  Number of large sectors. */
  BYTE       abReserved[6];  /*  Reserved. */
  USHORT     cCylinders;                       /*  Number of cylinders defined for the physical device. */
  BYTE       bDeviceType;                      /*  Physical layout of the specified device. */
  USHORT     fsDeviceAttr;                     /*  A bit field that returns flag information about the specified drive. */
} BIOSPARAMETERBLOCK;

typedef   BIOSPARAMETERBLOCK   * PBIOSPARAMETERBLOCK ;