BPB structure

    The BPB is called the Bios Parameter Block. It appears in the first section of the boot sector. It holds information regarding the disk and some important information for disk manuplations. The information held by BPB is show below
 
 Offset form start of 
   BOOT SECTOR		      Size of the data         Description
 00   3 bytes JMP instruction to the BOOT instructions
 03   8 bytes OEM label of the disk
 11   2 bytes Bytes per sector
 13   1 byte  Sectors per cluster
 14   2 bytes  Sectors in BOOT
 16   1 byte  Number of  FAT copies
 17   2 bytes  Number of ROOT entries
 19   2 bytes  Sectors per logical disk
 21   1 byte Disk ID byte
 22   2 bytes Sectors per FAT copy
 24   2 bytes  Sectors per track
 26   2 bytes Number of heads
 28   2 bytes  Number of reserved sectors
 30   4 bytes  Total big sectors
 34  1 byte  Physical drive number
 35   1 byte Reserved
 36   1 byte  Extended boot signature
 37   4 bytes  Volume serial number
 40   1 byte  Volume label
 41   1 byte  FAT ID byte

            The information furnished by the BPB can be used in your programs for disk manuplations. To know about the implementation of the data in BPB see the discussion on Dos Diskette structure.

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