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The BPB is the first block of a FAT partition and describes all the critical details of how the disk is laid out.  There are variables that are system dependent often based on size of disk.

000000   EB 3C 90 4D 53 44 4F 53 - 35 2E 30 00 02 01 02 00    �<�MSDOS5.0 


000010   02 00 02 60 F4 F8 F3 00 - 3F 00 FF 00 20 00 00 00     `��� ? �    

000020   00 00 00 00 00 00 29 B7 - E1 51 58 4E 4F 20 4E 41          )��QXNO NA

000030   4D 45 20 20 20 20 46 41 - 54 31 36 20 20 20 33 C9    ME    FAT16   3�

000040   8E D1 BC F0 7B 8E D9 B8 - 00 20 8E C0 FC BD 00 7C    �Ѽ�{�ٸ  ���� |

000050   38 4E 24 7D 24 8B C1 99 - E8 3C 01 72 1C 83 EB 3A    8N$}$����<
r��:

Details for FAT12 / FAT16

Bytes 0x0B-0x0C        00 02                0x200 or 512 bytes per sector

Byte 0x0D                01                1 sector per cluster.  Possible values are

                                       1,2,4,8,16,32,64

Bytes 0x0E-0x0F        02 00                2 reserved sectors  FAT starts at end of reserved sectors.

Byte 0x10                02                Number of FATs - 2 is normal

Bytes 0x11-0x12        00 02                0x200 or 512 root entries to the directory

Bytes 0x13-0x14        60 F4                0xF460  number of sectors

Byte 0x15                F8                Media type

                                               F8 fixed disk

                                               FB removeable disk

Bytes 0x16-0x17        F3 00                0xF3 Sectors per FAT

Bytes 0x18-0x19        00 3F                0x3F  Sectors per track - with modern disks this has no real meaning

Bytes 0x1A-0x1B        00 FF                0xFF  Number of heads, as above of no real meaning any more

Bytes 0x1C-0x1F        20 00 00 00        0x20  Hidden sectors.  This is the number of sectors from the physical start of the disk.

                                       ie, It should be the address of this sector

Bytes 0x20-0x23        00 00 00 00        The total number of sectors.  If the value fits in Bytes0x13-0x14  this field is blank

                                       If the number of sectors is greater than 16 bits, this field is used.

Bytes 0x26-0x2A        29 B7 E1 51        0x51E1B729  Volume serial number

Bytes 0x2B-0x35        NO NAME        Volume Name

Bytes 0x2c-0x3D        FAT16                File system, such as FAT12, FAT32

Bytes 0x3e-45                        Resevered for future use

Additions for FAT32

Bytes 0x24-0x27                        Sectors per file allocation table

Bytes 0x2c-0x2F                        Cluster number for directory

These are the values that are used in the Recover FAT function