FAT ==>
File Allocation Table
<file system> (FAT) The component of an MS-DOS or Windows 95 file system
which describes the files, directories, and free space on a hard disk or floppy
disk.
A disk is divided into partitions. Under the FAT file system each partition is
divided into clusters, each of 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 root
directory.
The FAT file system was originally created for the CP/M[?] operating system
where files were catalogued using 8-bit 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 allowed partitions of up to 2
gigabytes.
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 Windows 95 in 1996. It is not fully
backward compatible with the 16-bit and 8-bit FATs.
IDG article.
http://home.c2i.net/tkjoerne/os/fat.htm.
http://www.teleport.com/~brainy/.
http://209.67.75.168/hardware/fatgen.htm.
http://support.microsoft.com/support/kb/articles/q154/9/97.asp.
Compare: NTFS.
[How big is a FAT? Is the term used outside MS DOS? How long is a FAT16
filename?]
(2000-02-05)
Nearby terms:
fifth normal form « Fight-o-net « file « File
Allocation Table » File Attach » File
Composition » file compression
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