FAT File Systems - USB Mass Storage: Designing and Programming Devices and Embedded Hosts - page 185

Table 8-4: Recommended values for fields in a FAT32 boot sector.
Byte

Description Recommended Value

3 Identifying string “MSWin4.1”

11 Bytes per sector 512

14 Number of reserved sectors 32

16 FAT copies 2

44 First cluster of the root directory 2

48 FSInfo sector 1

50 Location of backup copy of boot record 6

the FAT. If any portion of the area reserved for one of the FATs becomes
damaged, the value in the Flags field can disable mirroring and specify
which FAT the file system should use.

File and Directory Data Region

As with FAT16, the file-and-directory data region consists of data clusters
that can store files and subdirectories. In a FAT32 system, this region stores
the root directory. The first data cluster is cluster 2.

Selecting a File System
Which FAT file system a volume is formatted for depends entirely on the
number of data clusters in the volume. The data clusters include all of the
clusters beginning with cluster 2 in the file-and-directory data region. They
don't include the MBR sector, reserved region, FAT region, or FAT16
root-directory sectors.

Cluster Sizes
The FAT32 specification says that a volume with fewer than 4085 data clus-
ters is formatted as FAT12, and a volume with 4085 to 65524 data clusters
is formatted as FAT16. Valid FAT12 cluster numbers are 2 to FEFh, so the
maximum number of FAT12 clusters is actually 4078. Valid FAT16 cluster
numbers are 2 to FFEFh, so the maximum number of FAT16 clusters is
actually 65518. A volume with 65527 or more data clusters is formatted as
FAT32.