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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 Table - FAT 12/16/32 characteristics).

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titleTable - FAT 12/16/32 characteristics


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



In µC/FS, you can enable support for FAT12, FAT16 and FAT32 individually: this means that you can enable only the FAT version that you need for your embedded system (see Appendix E, “μC/FS Configuration”.

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