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Anchor10040501004050 FAT12 / FAT16 / FAT32 Anchor10040511004051The 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).anchor

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FAT version1004056
HTML Table
summary
classPlain_Table
Table Row (tr)
Table Cell (td)
Anchor
10040541004054
Table Cell (td)
Anchor
1004056
0

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1004058
titleTable - FAT 12/16/32 characteristics


FAT version

Pointer size (Table entry size)

Table Cell (td)
Anchor

1004058

Max. size of disk

Table Cell (td) Anchor10040601004060

Free cluster marker

Table Cell (td) Anchor10040621004062

Damaged cluster marker

Table Cell (td) Anchor1004064

1004064

End of cluster chain marker

Table Row (tr) Table Cell (td) Anchor1004066

1004066

FAT12

Table Cell (td)anchor1004068

1004068

12 bits

Table Cell (td)anchor1004070

1004070

32 MB

Table Cell (td) Anchor10040721004072

0

Table Cell (td) Anchor10040741004074

0xff7

Table Cell (td) Anchor10040761004076

0xff8

Table Row (tr)td

Anchor10040781004078

FAT16

Table Cell (td) Anchor10040801004080

16 bits

Table Cell (td) Anchor1004082

1004082

2 GB

Table Cell (td) Anchor10040841004084

0

Table Cell (td) Anchor1004086

1004086

0xfff7

Table Cell (td) Anchor10040881004088

0xfff8

tr

Table Cell (td) Anchor10040901004090

FAT32

Table Cell (td) Anchor1004092

1004092

32 bits

Table Cell (td) Anchor10040941004094

8 TB

Table Cell (td) Anchor10040961004096

0

td

Anchor10040981004098

0x0fff fff7

Table Cell (td) Anchor10041001004100

0x0fff fff8

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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 EAppendix E, “μC/FS Configuration” on page 497. Anchor10041061004106

FAT32 introduced some innovations: Anchor10041071004107

  • The root directory in the earlier systems was a fixed size; i.e., when the medium is formatted, the maximum number of files that could be created in the root directory (typically 512) is set. In FAT32, the root directory is dynamically resizable, like all other directories.

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  • Two special sectors have been added to the volume: the FS info sector and the backup boot sector. The former stores information convenient to the operation of the host, such as the last used cluster. The latter is a copy of the first disk sector (the boot sector), in case the original is corrupted.