The earliest version of FAT, the file system integrated into MS-DOS, is now called FAT12, so-called because each cluster address in the File Allocation Table is 12 bits long. This limits disk size to approximately 32 MB. Extensions to 16- and 32-bit addresses (i.e., FAT16 and FAT32), expand support to 2 GB and 8 TB, respectively (see ).
FAT version | Pointer size (Table entry size) | Max. size of disk | Free cluster marker | Damaged cluster marker | End of cluster chain marker |
FAT12 | 12 bits | 32 MB | 0 | 0xff7 | 0xff8 |
FAT16 | 16 bits | 2 GB | 0 | 0xfff7 | 0xfff8 |
FAT32 | 32 bits | 8 TB | 0 | 0x0fff fff7 | 0x0fff fff8 |
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