Offset (from the start of the standard boot record)	Length (in bytes)	Meaning
36	1	Drive number. The value here should be identical to the value returned by BIOS interrupt 0x13, or passed in the DL register; i.e. 0x00 for a floppy disk and 0x80 for hard disks. This number is useless because the media is likely to be moved to another machine and inserted in a drive with a different drive number.
37	1	Flags in windows NT. Reserved otherwise.
38	1	Signature (must be 0x28 or 0x29).
39	4	VolumeID 'Serial' number. Used for tracking volumes between computers. You can ignore this if you want.
43	11	Volume label string. This field is padded with spaces.
54	8	System identifier string. This field is a string representation of the FAT file system type. It is padded with spaces. The spec says never to trust the contents of this string for any use.
62	448	Boot code.
510	2	0xAA55 bootable partition signature.

Offset (from the start of the standard boot record)	Length (in bytes)	Meaning
36	4	Sectors per FAT. The size of the FAT in sectors.
40	2	Flags.
42	2	FAT version number. The high byte is the major version and the low byte is the minor version. FAT drivers should respect this field.
44	4	The cluster number of the root directory. Often this field is set to 2.
48	2	The cluster number of the FSInfo structure.
50	2	The cluster number of the backup boot sector.
52	12	Reserved. When the volume is formated these bytes should be zero.
64	1	Drive number. The values here are identical to the values returned by the BIOS interrupt 0x13. 0x00 for a floppy disk and 0x80 for hard disks.
65	1	Flags in windows NT. Reserved otherwise.
66	1	Signature (must be 0x28 or 0x29).
67	4	VolumeID 'Serial' number. Used for tracking volumes between computers. You can ignore this if you want.
71	11	Volume label string. This field is padded with spaces.
82	8	System identifier string. Always "FAT32 ". The spec says never to trust the contents of this string for any use.
90	420	Boot code.
510	2	0xAA55 bootable partition signature.