FAT
File Allocation Table (FAT) was introduced with DOS v1.0 (and possibly CP/M), supposedly written by Bill Gates. FAT is a very simple filesystem which is nothing more than a singular linked list of clusters. FAT filesystems use very little memory and is one of, if not the, most basic filesystem in existance today.
About FAT
There are two versions of this simplified FAT, FAT12 and FAT16. FAT12 was designed for floppy disks and can manage a maximum size of 16mb using 12bit cluster numbers. FAT16 was designed for early hard disks and could handle a maximum size of 64kb * cluster_size. The larger the hard disk, the larger the cluster size would be, which lead to large amounts of "slack space" on the disk.
FAT12+FAT16 filesystems have fixed size for filenames of "8.3" and limited support for file attributes. You could also read the FAT12 document. You could also check out the FAT tutorial reported by Kemp.
VFAT
VFAT is an extension of FAT16 and FAT12 that has the ability to use long filenames (up to 255 characters i think). First introduced by Windows95, it uses a "cludge" whereby long filenames are marked with an "volume label"; attribute and filenames are subsequently stored in the 8.3 format in sequential directory entries. (This is a bit of an oversimplification, but close enough).
FAT32
FAT32 was introduced to us by Windows95-B and Windows98. FAT32 solved some of FAT's problems. No more 64kb max clusters! FAT32, as its name suggests, can handle a maximum of 4gig clusters per partition. This enables very large hard disks to still maintain very small cluster sizes and thus reduce slack space between files.
Is FAT32 really able to handle 4G clusters ? last time i looked to a FAT table, it looked to have last 4 bits cleared all the time, including the 'end of chain' tag, giving me the feeling that it was somehow more a "FAT28" than "FAT32" -- PypeClicker
Correct - FAT32 is actually only FAT28. Top 4 bits are currently "Undefined" (according to Microsoft's specification). Note that this does not mean 'top four bits should be "0"' - they should be honored. This means that if you need to alter a FAT entry, and the top 4 bits contain 1001, you should write it back to disk containing 1001 and not 0000. -- djhayman
Implementation Details
