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Reserved sector count. The number of sectors before the first FAT in the file
system image (including boot sector). Typically 1 for FAT12/FAT16 and 32 for
FAT32.
Number of file allocation table following the reserved sectors. Almost always 2.
The second FAT is used by recovery program if the first FAT is corrupted.
Maximum number of root directory entries
18
. This value should always be such
that the root directory ends on a sector boundary (i.e. such that its size becomes a
multiple of the sector size). 0 for FAT32.
Total number of sectors on the drive. If the size of the drive is greater than 32MB,
this field is set to zero and the number of sectors is specified in the huge number
of sectors field at offset 0x20 (HSECTS). 0 for FAT32
Media descriptor: Usually 0xF8 for Hard disk. Same value of media descriptor
should be repeated as first byte of each copy of FAT.
Number of Sectors per File Allocation Table
Number of Sectors per single Track
Number of heads on the drive
Huge number of Sectors (when more than 65535 sectors) otherwise, see
NSECTS at offset 0x13. This field allow support for drives larger than 32MB
10.6.1.1 Extended BIOS Parameter Block used by FAT12 and FAT16:
Drive ID: Specifies whether the drive is the first hard disk drive (value 0x80) or not
(value 0x00). Used internally by MS-DOS
Extended boot signature. Value is 0x29 (or 0x28).
Volume Label, padded with blanks (0x20).
FAT file system type, padded with blanks (0x20), e.g.: "FAT12 ", "FAT16 ". This
is not meant to be used to determine drive type; however, some utilities use it in
this way.
Operating system boot code
Boot sector signature (0x55 0xAA)
10.6.1.2 Extended BIOS Parameter Block used by FAT32:
First Cluster number of root directory
Sector number of FS Information Sector
Sector number of a copy of this boot sector
Physical Drive Number (Drive ID)
FAT file system type: "FAT32 "
Operating system boot code
This value should always be such that the root directory ends on a sector boundary (i.e. such that its size becomes a multiple
of the sector size).
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