Byte Offset |
Field Length |
Sample Value |
Meaning |
|
0x0B |
WORD |
0x0002 |
Bytes per Sector. The size of a hardware sector. For most disks in use in the
United States, the value of this field is 512. |
|
0x0D |
BYTE |
0x08 |
Sectors Per Cluster. The number of sectors in a cluster. The default cluster
size for a volume depends on the volume size and the file system. |
|
0x0E |
WORD |
0x0100 |
Reserved Sectors. The number of sectors from the Partition Boot Sector to the
start of the first file allocation table, including the Partition Boot Sector.
The minimum value is 1. If the value is greater than 1, it means that the
bootstrap code is too long to fit completely in the Partition Boot
Sector. |
|
0x10 |
BYTE |
0x02 |
Number of file allocation tables (FATs). The number of copies of the file
allocation table on the volume. Typically, the value of this field is
2. |
|
0x11 |
WORD |
0x0002 |
Root Entries. The total number of file name entries that can be stored in the
root folder of the volume. One entry is always used as a Volume Label. Files
with long filenames use up multiple entries per file. Therefore, the largest
number of files in the root folder is typically 511, but you will run out of
entries sooner if you use long filenames. |
|
0x13 |
WORD |
0x0000 |
Small Sectors. The number of sectors on the volume if the number fits in 16
bits (65535). For volumes larger than 65536 sectors, this field has a value of 0
and the Large Sectors field is used instead. |
|
0x15 |
BYTE |
0xF8 |
Media Type. Provides information about the media being used. A value of 0xF8
indicates a hard disk. |
|
0x16 |
WORD |
0xC900 |
Sectors per file allocation table (FAT). Number of sectors occupied by each
of the file allocation tables on the volume. By using this information, together
with the Number of FATs and Reserved Sectors, you can compute where the root
folder begins. By using the number of entries in the root folder, you can also
compute where the user data area of the volume begins. |
|
0x18 |
WORD |
0x3F00 |
Sectors per Track. The apparent disk geometry in use when the disk was
low-level formatted. |
|
0x1A |
WORD |
0x1000 |
Number of Heads. The apparent disk geometry in use when the disk was
low-level formatted. |
|
0x1C |
DWORD |
3F 00 00 00 |
Hidden Sectors. Same as the Relative Sector field in the Partition
Table. |
|
0x20 |
DWORD |
51 42 06 00 |
Large Sectors. If the Small Sectors field is zero, this field contains the
total number of sectors in the volume. If Small Sectors is nonzero, this field
contains zero.. |
|
0x24 |
BYTE |
0x80 |
Physical Disk Number. This is related to the BIOS physical disk number.
Floppy drives are numbered starting with 0x00 for the A disk. Physical hard
disks are numbered starting with 0x80. The value is typically 0x80 for hard
disks, regardless of how many physical disk drives exist, because the value is
only relevant if the device is the startup disk. |
|
0x25 |
BYTE |
0x00 |
Current Head. Not
used by the FAT file system. |
|
0x26 |
BYTE |
0x29 |
Signature. Must be either 0x28 or 0x29 in order to be recognized by
Windows NT. |
|
0x27 |
4 bytes |
CE 13 46 30 |
Volume Serial Number. A unique number that is created when you format the
volume. |
|
0x2B |
11 bytes |
NO NAME |
Volume Label. This field was used to store the volume label, but the volume
label is now stored as special file in the root directory. |
|
0x36 |
8 bytes |
FAT16 |
System ID. Either FAT12 or FAT16, depending on the format of the
disk. |
