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which can be one or more
sectors, depending on the size of
the partition. Each cluster is either allocated to a file or
directory or it is free (unused). A directory lists the name,
size, modification time and starting cluster of each file or
subdirectory it contains.
At the start of the partition is a table (the FAT) with one
entry for each cluster. Each entry gives the number of the
next cluster in the same file or a special value for "not
allocated" or a special value for "this is the last cluster in
the chain". The first few clusters after the FAT contain the
The FAT file system was originally created for the
CP/M[?]
addressing.
MS DOS's FAT allows only
8.3 filenames.
With the introduction of MS-DOS 4 an incompatible 16-bit FAT
(FAT16) with 32-kilobyte
clusters was introduced that
Microsoft later created
FAT32 to support partitions larger
than two gigabytes and
pathnames greater that 256
characters. It also allows more efficient use of disk space
since
clusters are four kilobytes rather than 32 kilobytes.
FAT32 was first available in
OEM Service Release 2 of
with the 16-bit and 8-bit FATs.
[How big is a FAT? Is the term used outside MS DOS? How long
is a FAT16 filename?]
(2000-02-05)