FAT32

FAT32 is an enhancement to the standard FAT file system. It is named FAT32 because it allows the use of 32-bit numbers to represent cluster numbers, instead of the 16-bit numbers used by standard FAT (which is also called FAT16 for that reason). FAT32 was introduced in Windows 95's OEM Service Release 2, also sometimes called Windows 95b and is supported by that version of Windows 95, and the version of DOS that comes with it. Earlier operating systems cannot read a disk volume formatted with FAT32.

FAT32 was created primarily for one reason: hard disk manufacturers began making mainstream hard disks larger than 2 GB in size, and FAT16 supports only a maximum of 2 GB per logical disk volume. FAT32 extends this up to 8 GB in its current implementation and can handle even larger disks using the same basic structures.

In addition to allowing much larger individual disk volumes, FAT32 saves wasted space due to slack, because it uses much smaller cluster sizes than FAT16 does. The tradeoff for this is that the number of clusters used is much larger, which can mean a small performance hit due to the extra amount of overhead required (plus extra memory to hold the larger FAT).

Aside from the difference in the way clusters are assigned and numbered, FAT32 is at its essence the same as regular FAT, and the descriptions of FAT file structures apply to FAT32 as well. The matter of using regular FAT16 vs. FAT32, and choosing partition and cluster sizes, is discussed in detail here.

See this Windows 95 OSR2 FAQ for more details on FAT32 and other OSR2 features.

Next: Virtual FAT (VFAT)