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<p align=center style='text-align:center'><strong><u><span style='font-size:
13.5pt'>FAT32 Structure Information - Written by Jack Dobiash</span></u></strong></p>
<p align=center style='text-align:center'><em><span style='font-size:10.0pt'>Updated
: December 4<sup>th</sup>, 2005</span></em></p>
<p>Looking for FAT16 info? Go <a
href="http://home.teleport.com/~brainy/fat16.htm">here</a>.<br>
Looking for Information on how to Read and Write to your Hard Drive? Go <a
href="http://home.teleport.com/~brainy/diskaccess.htm">here</a>.</p>
<p>Microsoft has Released Information on the FAT32 File System! Go <a
href="http://home.teleport.com/~brainy/fatgen102.pdf">here</a> to get it!</p>
<p>I've written this page for anyone who wishes to write software that can do
low-level reading and writing of a hard drive, and needs to know what the
underlying structure of a FAT32 Drive is, in order to interpret the information
properly. Basically I've searched all over the web, and have compiled
this information in one spot. Hopefully it can be of use to
someone. I don't guarantee that all of this information is correct or
complete, but so far is seems to have been working for me. </p>
<p>A lot of the number references I've made in this document are in
Hexadecimal. Any that are have an 'h' after them. Also, just in
case my terminology may be different from yours; a 'WORD' is 2 Bytes and a
'DOUBLE WORD' is 4 Bytes. </p>
<p> </p>
<p><strong><u>Master Boot Record</u></strong></p>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'>
<p>The Master Boot Record is the same for pretty much all Operating
Systems. It is located on the first Sector of the Hard Drive, at Cylinder
0, Head 0, Sector 1. It is the first piece of code that your computer
runs after it has checked all of your hardware (POST) and turned control of
loading software over the hard drive. It also contains the partition
table, which defines the different sections of your hard drive. Basically
if anything happens to this little 512 byte section, your hard drive is brain
dead. Kinda scary, eh? :)</p>
</blockquote>
<table class=MsoNormalTable border=1 cellpadding=0 width=503 style='width:377.6pt'
height=79>
<tr style='height:18.75pt'>
<td width=54 style='width:40.45pt;padding:.75pt .75pt .75pt .75pt;height:
18.75pt'>
<p class=MsoNormal>Offset</p>
</td>
<td width=329 style='width:247.05pt;padding:.75pt .75pt .75pt .75pt;
height:18.75pt'>
<p class=MsoNormal>Description</p>
</td>
<td width=112 style='width:84.1pt;padding:.75pt .75pt .75pt .75pt;height:
18.75pt'>
<p class=MsoNormal>Size</p>
</td>
</tr>
<tr style='height:18.75pt'>
<td width=54 style='width:40.45pt;padding:.75pt .75pt .75pt .75pt;height:
18.75pt'>
<p class=MsoNormal>000h</p>
</td>
<td width=329 style='width:247.05pt;padding:.75pt .75pt .75pt .75pt;
height:18.75pt'>
<p class=MsoNormal>Executable Code (Boots Computer)</p>
</td>
<td width=112 style='width:84.1pt;padding:.75pt .75pt .75pt .75pt;height:
18.75pt'>
<p class=MsoNormal>446 Bytes</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=54 style='width:40.45pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>1BEh</p>
</td>
<td width=329 style='width:247.05pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1st Partition Entry (See Next Table)</p>
</td>
<td width=112 style='width:84.1pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>16 Bytes</p>
</td>
</tr>
<tr style='height:12.75pt'>
<td width=54 style='width:40.45pt;padding:.75pt .75pt .75pt .75pt;height:
12.75pt'>
<p class=MsoNormal>1CEh</p>
</td>
<td width=329 style='width:247.05pt;padding:.75pt .75pt .75pt .75pt;
height:12.75pt'>
<p class=MsoNormal>2nd Partition Entry</p>
</td>
<td width=112 style='width:84.1pt;padding:.75pt .75pt .75pt .75pt;height:
12.75pt'>
<p class=MsoNormal>16 Bytes</p>
</td>
</tr>
<tr style='height:9.0pt'>
<td width=54 style='width:40.45pt;padding:.75pt .75pt .75pt .75pt;height:
9.0pt'>
<p class=MsoNormal>1DEh</p>
</td>
<td width=329 style='width:247.05pt;padding:.75pt .75pt .75pt .75pt;
height:9.0pt'>
<p class=MsoNormal>3rd Partition Entry</p>
</td>
<td width=112 style='width:84.1pt;padding:.75pt .75pt .75pt .75pt;height:
9.0pt'>
<p class=MsoNormal>16 Bytes</p>
</td>
</tr>
<tr style='height:15.0pt'>
<td width=54 style='width:40.45pt;padding:.75pt .75pt .75pt .75pt;height:
15.0pt'>
<p class=MsoNormal>1EEh</p>
</td>
<td width=329 style='width:247.05pt;padding:.75pt .75pt .75pt .75pt;
height:15.0pt'>
<p class=MsoNormal>4th Partition Entry</p>
</td>
<td width=112 style='width:84.1pt;padding:.75pt .75pt .75pt .75pt;height:
15.0pt'>
<p class=MsoNormal>16 Bytes</p>
</td>
</tr>
<tr style='height:12.0pt'>
<td width=54 style='width:40.45pt;padding:.75pt .75pt .75pt .75pt;height:
12.0pt'>
<p class=MsoNormal>1FEh</p>
</td>
<td width=329 style='width:247.05pt;padding:.75pt .75pt .75pt .75pt;
height:12.0pt'>
<p class=MsoNormal>Boot Record Signature (55h AAh)</p>
</td>
<td width=112 style='width:84.1pt;padding:.75pt .75pt .75pt .75pt;height:
12.0pt'>
<p class=MsoNormal>2 Bytes</p>
</td>
</tr>
</table>
<p><br>
<strong>Partition Entry (Part of MBR)</strong></p>
<table class=MsoNormalTable border=1 cellpadding=0 width=523 style='width:392.25pt'
height=236>
<tr style='height:5.25pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
5.25pt'>
<p class=MsoNormal>Offset</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:5.25pt'>
<p class=MsoNormal>Description</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
5.25pt'>
<p class=MsoNormal>Size</p>
</td>
</tr>
<tr style='height:6.0pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
6.0pt'>
<p class=MsoNormal>00h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:6.0pt'>
<p class=MsoNormal>Current State of Partition (00h=Inactive, 80h=Active)</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
6.0pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:13.5pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
13.5pt'>
<p class=MsoNormal>01h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:13.5pt'>
<p class=MsoNormal>Beginning of Partition - Head</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
13.5pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:14.25pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
14.25pt'>
<p class=MsoNormal>02h </p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:14.25pt'>
<p class=MsoNormal>Beginning of Partition - Cylinder/Sector (See Below)</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
14.25pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:11.25pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
11.25pt'>
<p class=MsoNormal>04h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:11.25pt'>
<p class=MsoNormal>Type of Partition (See List Below)</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
11.25pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:9.75pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
9.75pt'>
<p class=MsoNormal>05h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:9.75pt'>
<p class=MsoNormal>End of Partition - Head</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
9.75pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:11.25pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
11.25pt'>
<p class=MsoNormal>06h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:11.25pt'>
<p class=MsoNormal>End of Partition - Cylinder/Sector</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
11.25pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>08h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Number of Sectors Between the MBR and the First Sector in
the Partition</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=47 style='width:35.25pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>0Ch</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Number of Sectors in the Partition</p>
</td>
<td width=130 style='width:97.5pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
</table>
<p><br>
<strong>Cylinder/Sector Encoding</strong></p>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'>
<p>I guess back in the days of 10MB hard drives and 8086's, code was at a
premium. So they did everything they could to preserve space.
Unfortunately now we have to live with it, but luckily they created new ways of
translating the system so the 1024 Cylinder Limit (2^10) isn't too big of a
problem, for newer computers, at least. Older ones usually need some
sort of Disk Overlay program to make them see the whole hard drive.
</p>
<p>Anyway, to get the Sector out of this, you need to apply an AND mask ($3F)
to it. To get the Cylinder, you take the high byte and OR it with the
low byte that has been AND masked with ($C0) and then Shifted Left Two.
It's not very easy to explain, so I'll just show you how I did it with two
routines I made (In Pascal) for Encoding and Decoding the
Cylinder/Sector. Hopefully even if you don't know Pascal you'll be able
to read it.</p>
<p>Function CylSecEncode(Cylinder, Sector : Word) : Word;<br>
Begin<br>
CylSecEncode := (Lo(Cylinder) shl 8) or (Hi(Cylinder) shl 6)
or Sector;<br>
End;<br>
<br>
Procedure CylSecDecode(Var Cylinder, Sector : Word; CylSec : Word);<br>
Begin<br>
Cylinder := Hi(CylSec) or ((Lo(CylSec) and $C0) shl 2);<br>
Sector := (CylSec and $3F);<br>
End;</p>
</blockquote>
<table class=MsoNormalTable border=1 cellpadding=0 width=418 style='width:313.5pt'
height=48>
<tr style='height:17.25pt'>
<td width=10 style='width:7.5pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>15</p>
</td>
<td width=13 style='width:9.75pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>14</p>
</td>
<td width=18 style='width:13.5pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>13</p>
</td>
<td width=10 style='width:.1in;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>12</p>
</td>
<td width=12 style='width:9.0pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>11</p>
</td>
<td width=20 style='width:15.0pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>10</p>
</td>
<td width=19 style='width:14.25pt;padding:.75pt .75pt .75pt .75pt;height:
17.25pt'>
<p class=MsoNormal>9</p>
</td>
<td width=20 style='width:15.0pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>8</p>
</td>
<td width=36 style='width:27.0pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>7</p>
</td>
<td width=29 style='width:21.75pt;padding:.75pt .75pt .75pt .75pt;height:
17.25pt'>
<p class=MsoNormal>6</p>
</td>
<td width=20 style='width:15.0pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>5</p>
</td>
<td width=22 style='width:16.5pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>4</p>
</td>
<td width=21 style='width:15.75pt;padding:.75pt .75pt .75pt .75pt;height:
17.25pt'>
<p class=MsoNormal>3</p>
</td>
<td width=22 style='width:16.5pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>2</p>
</td>
<td width=25 style='width:18.75pt;padding:.75pt .75pt .75pt .75pt;height:
17.25pt'>
<p class=MsoNormal>1</p>
</td>
<td width=23 style='width:17.25pt;padding:.75pt .75pt .75pt .75pt;height:
17.25pt'>
<p class=MsoNormal>0</p>
</td>
</tr>
<tr style='height:9.75pt'>
<td width=184 colspan=8 style='width:138.0pt;padding:.75pt .75pt .75pt .75pt;
height:9.75pt'>
<p class=MsoNormal>Cylinder Bits 7 to 0</p>
</td>
<td width=67 colspan=2 style='width:50.25pt;padding:.75pt .75pt .75pt .75pt;
height:9.75pt'>
<p class=MsoNormal>Cylinder Bits 9+8</p>
</td>
<td width=149 colspan=6 style='width:111.75pt;padding:.75pt .75pt .75pt .75pt;
height:9.75pt'>
<p class=MsoNormal>Sector Bits 5 to 0</p>
</td>
</tr>
</table>
<p><br>
<strong>Partition Type Listing</strong></p>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'>
<p>There are more than just these shown, but I've only included that ones
relevant to MS Operating Systems.</p>
</blockquote>
<table class=MsoNormalTable border=1 cellpadding=0 width=418 style='width:313.5pt'
height=57>
<tr style='height:17.25pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:17.25pt'>
<p class=MsoNormal>Value</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:17.25pt'>
<p class=MsoNormal>Description</p>
</td>
</tr>
<tr style='height:7.5pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:7.5pt'>
<p class=MsoNormal>00h</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:7.5pt'>
<p class=MsoNormal>Unknown or Nothing</p>
</td>
</tr>
<tr style='height:9.75pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:9.75pt'>
<p class=MsoNormal>01h</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:9.75pt'>
<p class=MsoNormal>12-bit FAT</p>
</td>
</tr>
<tr>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal>04h</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal>16-bit FAT (Partition Smaller than 32MB)</p>
</td>
</tr>
<tr style='height:6.0pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:6.0pt'>
<p class=MsoNormal>05h</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:6.0pt'>
<p class=MsoNormal>Extended MS-DOS Partition</p>
</td>
</tr>
<tr style='height:5.25pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:5.25pt'>
<p class=MsoNormal>06h</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:5.25pt'>
<p class=MsoNormal>16-bit FAT (Partition Larger than 32MB)</p>
</td>
</tr>
<tr style='height:4.5pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:4.5pt'>
<p class=MsoNormal>0Bh</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:4.5pt'>
<p class=MsoNormal>32-bit FAT (Partition Up to 2048GB)</p>
</td>
</tr>
<tr style='height:7.5pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:7.5pt'>
<p class=MsoNormal>0Ch</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:7.5pt'>
<p class=MsoNormal>Same as 0BH, but uses LBA<sub>1</sub> 13h Extensions</p>
</td>
</tr>
<tr style='height:9.0pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:9.0pt'>
<p class=MsoNormal>0Eh</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:9.0pt'>
<p class=MsoNormal>Same as 06H, but uses LBA<sub>1</sub> 13h Extensions</p>
</td>
</tr>
<tr style='height:.75pt'>
<td width=52 style='width:39.0pt;padding:.75pt .75pt .75pt .75pt;height:.75pt'>
<p class=MsoNormal>0Fh</p>
</td>
<td width=354 style='width:265.5pt;padding:.75pt .75pt .75pt .75pt;
height:.75pt'>
<p class=MsoNormal>Same as 05H, but uses LBA<sub>1</sub> 13h Extensions</p>
</td>
</tr>
</table>
<p><br>
<strong><u>Reading Multiple Partitions</u></strong></p>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'>
<p>Although having multiple partitions in FAT32 isn't as likely as in FAT16, it
still works the same way. The first partition is the Primary Partition, and
everything else is stored in the Extended Partition. It's a little tricky
when it comes to reading those extra partitions though (not a lot, just a
little). The first record in the partition table shows where the Primary
partition is (how big it is, where it starts, and where it ends). The
second entry in the partition table shows where the Entire Extended Partition
is (which may include more than just one partition). To read any more
partitions, you go to the where it says the Extended Partition starts, and read
the first sector. It acts just like the MBR. It'll have blank where
the code is supposed to be, and in the partition table it will have for it's
first entry the next Partition in the Drive, and if there are anymore, there
will be another Extended partition, just like before. However, all
references to Sector Numbers are made using the that new MBR point as the
reference, making it a virtual drive. Just incase this doesn't make much
sense (and by the way I explain things I can understand if it doesn't), let me
show you how a drive with three partitions is setup.</p>
<p>MBR of Whole Drive</p>
<p> Entry #1 - Points to Partition #1<br>
Entry #2 - Points to the Entire Extended Partition</p>
<p>You would read the first sector of that Extended Partition, and see another
MBR Structure.</p>
<p>MBR of Extended Partition</p>
<p> Entry #1 - Points to Partition #2<br>
Entry #2 - Points to Rest of Extended Partition after
Partition #2</p>
<p>Now, all references to Sector Numbers (most specifically the entry at Offset
08h) in those Entries wouldn't be referenced from the start of the drive, but
from the start of the Extended Partition. However, the CHS (Cylinder,
Head, Sector) numbers would still be right.</p>
<p>Once again, you would read the first sector of that Extended Partition, and
see the next MBR.</p>
<p>MBR of Rest of Extended Partition</p>
<p> Entry #1 - Points to Partition #3<br>
No Entry #2, since this was the Last Partition</p>
<p>If there were another partition, the pattern would continue just like
before, until the last one was reached.</p>
</blockquote>
<p> </p>
<p><br>
<strong><u>FAT32 Boot Record</u></strong></p>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'>
<p>This information is located in the first sector of every partition.</p>
</blockquote>
<table class=MsoNormalTable border=1 cellpadding=0 width=518 style='width:388.5pt'
height=192>
<tr style='height:14.25pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:14.25pt'>
<p class=MsoNormal>Offset</p>
</td>
<td width=329 style='width:246.75pt;padding:.75pt .75pt .75pt .75pt;
height:14.25pt'>
<p class=MsoNormal>Description</p>
</td>
<td width=110 style='width:82.5pt;padding:.75pt .75pt .75pt .75pt;height:
14.25pt'>
<p class=MsoNormal>Size</p>
</td>
</tr>
<tr style='height:7.5pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:7.5pt'>
<p class=MsoNormal>00h</p>
</td>
<td width=329 style='width:246.75pt;padding:.75pt .75pt .75pt .75pt;
height:7.5pt'>
<p class=MsoNormal>Jump Code + NOP</p>
</td>
<td width=110 style='width:82.5pt;padding:.75pt .75pt .75pt .75pt;height:
7.5pt'>
<p class=MsoNormal>3 Bytes</p>
</td>
</tr>
<tr style='height:18.75pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:18.75pt'>
<p class=MsoNormal>03h</p>
</td>
<td width=329 style='width:246.75pt;padding:.75pt .75pt .75pt .75pt;
height:18.75pt'>
<p class=MsoNormal>OEM Name (Probably MSWIN4.1)</p>
</td>
<td width=110 style='width:82.5pt;padding:.75pt .75pt .75pt .75pt;height:
18.75pt'>
<p class=MsoNormal>8 Bytes</p>
</td>
</tr>
<tr style='height:4.5pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:4.5pt'>
<p class=MsoNormal>0Bh</p>
</td>
<td width=329 style='width:246.75pt;padding:.75pt .75pt .75pt .75pt;
height:4.5pt'>
<p class=MsoNormal>Bytes Per Sector</p>
</td>
<td width=110 style='width:82.5pt;padding:.75pt .75pt .75pt .75pt;height:
4.5pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:5.25pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:5.25pt'>
<p class=MsoNormal>0Dh</p>
</td>
<td width=329 style='width:246.75pt;padding:.75pt .75pt .75pt .75pt;
height:5.25pt'>
<p class=MsoNormal>Sectors Per Cluster</p>
</td>
<td width=110 style='width:82.5pt;padding:.75pt .75pt .75pt .75pt;height:
5.25pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:9.0pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:9.0pt'>
<p class=MsoNormal>0Eh</p>
</td>
<td width=329 style='width:246.75pt;padding:.75pt .75pt .75pt .75pt;
height:9.0pt'>
<p class=MsoNormal>Reserved Sectors</p>
</td>
<td width=110 style='width:82.5pt;padding:.75pt .75pt .75pt .75pt;height:
9.0pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:5.25pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:5.25pt'>
<p class=MsoNormal>10h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:5.25pt'>
<p class=MsoNormal>Number of Copies of FAT</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:5.25pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:3.0pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:3.0pt'>
<p class=MsoNormal>11h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:3.0pt'>
<p class=MsoNormal>Maximum Root Directory Entries (N/A for FAT32)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:3.0pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:3.75pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:3.75pt'>
<p class=MsoNormal>13h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:3.75pt'>
<p class=MsoNormal>Number of Sectors in Partition Smaller than 32MB (N/A for
FAT32)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:3.75pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:6.0pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:6.0pt'>
<p class=MsoNormal>15h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:6.0pt'>
<p class=MsoNormal>Media Descriptor (F8h for Hard Disks)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:6.0pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:3.0pt'>
<td width=60 style='width:45.0pt;padding:.75pt .75pt .75pt .75pt;height:3.0pt'>
<p class=MsoNormal>16h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:3.0pt'>
<p class=MsoNormal>Sectors Per FAT in Older FAT Systems (N/A for FAT32)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:3.0pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>18h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>Sectors Per Track</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:17.25pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
17.25pt'>
<p class=MsoNormal>1Ah</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:17.25pt'>
<p class=MsoNormal>Number of Heads</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:17.25pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>1Ch</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Number of Hidden Sectors in Partition</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>20h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Number of Sectors in Partition</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>24h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Number of Sectors Per FAT</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>28h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Flags (Bits 0-4 Indicate Active FAT Copy) (Bit 7 Indicates
whether FAT Mirroring is Enabled or Disabled <Clear is Enabled>) (If
FAT Mirroring is Disabled, the FAT Information is only written to the copy
indicated by bits 0-4)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>2Ah</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Version of FAT32 Drive (High Byte = Major Version, Low
Byte = Minor Version)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>2Ch</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Cluster Number of the Start of the Root Directory</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>30h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Sector Number of the File System Information Sector (See Structure
Below) (Referenced from the Start of the Partition)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>32h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Sector Number of the Backup Boot Sector (Referenced from
the Start of the Partition)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>34h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Reserved</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>12 Bytes</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>40h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Logical Drive Number of Partition</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>41h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Unused (Could be High Byte of Previous Entry)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>42h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Extended Signature (29h)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Byte</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>43h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Serial Number of Partition</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>47h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Volume Name of Partition</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>11 Bytes</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>52h</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>FAT Name (FAT32)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>8 Bytes</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>5Ah</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Executable Code</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>420 Bytes</p>
</td>
</tr>
<tr style='height:16.5pt'>
<td width=61 style='width:45.75pt;padding:.75pt .75pt .75pt .75pt;height:
16.5pt'>
<p class=MsoNormal>1FEh</p>
</td>
<td width=328 style='width:246.0pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>Boot Record Signature (55h AAh)</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:16.5pt'>
<p class=MsoNormal>2 Bytes</p>
</td>
</tr>
</table>
<p><br>
<strong><u>File System Information Sector</u></strong></p>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'>
<p>Usually this is the Second Sector of the partition, although since there is a
reference in the Boot Sector to it, I'm assuming it can be moved around.
I never got a complete picture of this one. Although I do know where the
important fields are at.</p>
</blockquote>
<table class=MsoNormalTable border=1 cellpadding=0 width=521 style='width:390.75pt'
height=65>
<tr style='height:9.75pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
9.75pt'>
<p class=MsoNormal>Offset</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:9.75pt'>
<p class=MsoNormal>Description</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:9.75pt'>
<p class=MsoNormal>Size</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>00h</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>First Signature (52h 52h 61h 41h)</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>04h</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>Unknown, Currently (Might just be Null)</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>480 Bytes</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>1E4h</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>Signature of FSInfo Sector (72h 72h 41h 61h)</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>1E8h</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>Number of Free Clusters (Set to -1 if Unknown)</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>1ECh</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>Cluster Number of Cluster that was Most Recently
Allocated.</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>1 Double Word</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>1F0h</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>Reserved</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>12 Bytes</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>1FCh</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>Unknown or Null</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>2 Bytes</p>
</td>
</tr>
<tr style='height:10.5pt'>
<td width=63 style='width:47.25pt;padding:.75pt .75pt .75pt .75pt;height:
10.5pt'>
<p class=MsoNormal>1FEh</p>
</td>
<td width=331 style='width:248.25pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>Boot Record Signature (55h AAh)</p>
</td>
<td width=109 style='width:81.75pt;padding:.75pt .75pt .75pt .75pt;
height:10.5pt'>
<p class=MsoNormal>2 Bytes</p>
</td>
</tr>
</table>
<p><br>
<strong><u>FAT32 Drive Layout</u></strong></p>
<table class=MsoNormalTable border=1 cellpadding=0 width=521 style='width:390.75pt'
height=64>
<tr style='height:17.25pt'>
<td width=374 style='width:280.5pt;padding:.75pt .75pt .75pt .75pt;
height:17.25pt'>
<p class=MsoNormal>Offset</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:17.25pt'>
<p class=MsoNormal>Description</p>
</td>
</tr>
<tr style='height:7.5pt'>
<td width=374 style='width:280.5pt;padding:.75pt .75pt .75pt .75pt;
height:7.5pt'>
<p class=MsoNormal>Start of Partition</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:7.5pt'>
<p class=MsoNormal>Boot Sector</p>
</td>
</tr>
<tr style='height:9.0pt'>
<td width=374 style='width:280.5pt;padding:.75pt .75pt .75pt .75pt;
height:9.0pt'>
<p class=MsoNormal>Start + # of Reserved Sectors</p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:9.0pt'>
<p class=MsoNormal>Fat Tables</p>
</td>
</tr>
<tr style='height:9.0pt'>
<td width=374 style='width:280.5pt;padding:.75pt .75pt .75pt .75pt;
height:9.0pt'>
<p class=MsoNormal>Start + # of Reserved + (# of Sectors Per FAT * 2)
<Assuming that FAT Mirroring is Enabled, I personally haven't seen a case where
it wasn't, but I guess there is always the possibility></p>
</td>
<td width=111 style='width:83.25pt;padding:.75pt .75pt .75pt .75pt;
height:9.0pt'>
<p class=MsoNormal>Data Area (Starts with Cluster #2)</p>
</td>
</tr>
</table>
<p> </p>
<p><strong><u>Cluster Meaning</u></strong></p>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'>
<p>A Cluster is a Group of Sectors on the Hard Drive that have information in
them. A 4K Cluster has 8 Sectors in it (512*8=4096). Each Cluster
is given a spot in the FAT Table. When you look at an Entry in the FAT,
the number there tells you whether or not that cluster has data in it, and if
so, if it is the end of the data or there is another cluster after it.
All Data on a Partition starts with Cluster #2. If the FAT Entry
is 0, then there is no data in that cluster. If the FAT Entry is
0FFFFFFFh, then it is the last entry in the chain. </p>
<p>This is one of my biggest holes in my information. I am unable to find
anyplace that shows what numbers mean what when it comes to the FAT
table. I was able to tell the end of the chain just by looking at a FAT32
Drive, but I don't know what stands for a BAD Cluster or what the maximum valid
number for showing data is. </p>
<p>For now, you can calculate the maximum valid cluster in a partition with
this formula:</p>
<p>( (# of Sectors in Partition) - (# of Sectors per Fat * 2) - (# of Reserved
Sectors) ) / (# of Sectors per Cluster)</p>
<p>If there is any remainder in the answer to that formula, it just means that
there were a few extra clusters at the end of the partition (probably not
enough to make another cluster), so you can just get rid of anything after the
decimal point.</p>
<p> Thanks to Andrew Clausen for pointing this formula out to
me.</p>
</blockquote>
<p> </p>
<p><strong><u>Directory Table</u></strong></p>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'>
<p>Another aspect when looking at a File System at Low Level is the Directory
Table. The Directory Table is what stores all of the File and Directory
Entries. Basically there is only one difference between the Directory
Table of FAT16 and FAT32, so go <a
href="http://home.teleport.com/~brainy/lfn.htm">here</a> to look at FAT16's
Structure. The Difference is : the Reserved OS/2 Byte (Offset 20
[14h]) in the Short Filename Structure is replaced with the High Word of the
Cluster Number (since it's now 4 bytes instead of 2).</p>
</blockquote>
<p> </p>
<p>Footnotes</p>
<p>1 - LBA = Logical Block Addressing - Uses the Int 13h Extensions built into
newer BIOS's to access data above the 8GB barrier, or to access strictly in LBA
mode, instead of CHS (Cylinder, Head, Sector).</p>
<p style='margin-left:.5in'>To support disk drives larger than 137 GB, modern
BIOSs<br>
have extensions for "48-bit LBA" (a/k/a "LBA48")
disk<br>
access. The specifications are here:<br>
<a
href="http://www.t13.org/Documents/UploadedDocuments/docs2004/d1572r3-EDD3.pdf">http://www.t13.org/Documents/UploadedDocuments/docs2004/d1572r3-EDD3.pdf</a>
or<br>
<a
href="http://www.t13.org/Documents/UploadedDocuments/docs2004/d1572r3-EDD3.doc">http://www.t13.org/Documents/UploadedDocuments/docs2004/d1572r3-EDD3.doc</a> </p>
<p style='margin-left:.5in'>(Thanks to Dave Burton for this Information)</p>
<p style='margin-left:.5in'> </p>
<p align=center style='text-align:center'><a
href="http://home.teleport.com/~brainy">Home</a> <a
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Structure Information</a> <a
href="http://home.teleport.com/~brainy/diskaccess.htm">Disk Access Information</a>
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