FAT file system - Revision history

Jnc: +New cat

2023-06-12T17:15:59Z

+New cat

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Avoid redir

Jnc: clarify

2023-05-15T03:14:58Z

clarify

Tor: Fixed typo (superfluous "by")

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Fixed typo (superfluous "by")

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+file names

Jnc: Jnc moved page File Allocation Table to FAT file system: better name for it

2023-01-21T17:50:11Z

Jnc moved page File Allocation Table to FAT file system: better name for it

Jnc: Jnc moved page FAT to File Allocation Table: Formal name

2023-01-21T15:49:47Z

Jnc moved page FAT to File Allocation Table: Formal name

Jnc: Gives the basics

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Gives the basics

New page

The '''File Allocation Table''' (usually abbreviated to '''FAT''') if the name of a group of related [[file system]]s used in [[MS-DOS]] and early [[Microsoft Windows|Windows]] [[operating system]]s. The first was '''FAT12''' (used by [[floppy disk]]s), from which descended '''FAT16''' and '''FAT32''' (the last used by only by [[hard disk]]s).

The name comes from the way they indicate which [[disk block]]s of the [[disk]] are used by any given [[file]], and which blocks are free and available for use - the 'file allocation table'. (FAT file systems were not the first to use this approach; others OS's, such as [[Incompatible Timesharing System|ITS]], had used a similar approach long before.) The disk contains, at the start of the disk, a large [[array]] of entries, one for each 'cluster' (group of blocks) of the disk; each entry indicates whether that cluster is free (and thus available for allocation), or part of a file. For clusters which are part of a file, their entries in the FAT are used to tie them together. (For robustness, there are two identical copies of the FAT.)

The array elements are of size 12, 16 and 32 bits in FAT12, FAT16 and FAT32 file systems. FAT32 was a relatively late addition; it was added in [[Windows 95]] OSR 2.

Unlike the [[UNIX file system]], which strictly separates the functions of the ''naming'' of files (via [[directory|directories]]), and indicating ''where'' the files are stored, FAT file systems to some extent merge these two - again, like earlier file systems. The directory entry of a file indicates which cluster is the first cluster of the file; from there, FAT elements form a [[linked list]] of all the clusters in the file.

Like the Unix file system, most directories are stored in what are effectively files; the root directory is a special case, and is stored in a specially allocated area at the start of the disk.

{{semi-stub}}

==See also==

* [[BSD Fast File System]]

==External links==

* [https://learn.microsoft.com/en-US/windows/win32/fileio/exfat-specification exFAT file system specification] - also covers FAT12, FAT16 and FAR32
* [https://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html The FAT filesystem]

[[Category: File Systems]]
[[Category: Microsoft Operating Systems]]

← Older revision		Revision as of 17:15, 12 June 2023
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	[[Category: File Systems]]		[[Category: File Systems]]
		+	[[Category: PC Disk Formats]]
	[[Category: Microsoft Operating Systems]]		[[Category: Microsoft Operating Systems]]

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 For clusters which are part of a file, their entries in the FAT are used to tie them together. The array elements are of size 12, 16 and 32 bits in FAT12, FAT16 and FAT32 file systems. FAT32 was a relatively late addition; it was added in [[Windows 95]] OSR 2.
-Unlike the [[UNIX file system]], which strictly separates the functions of the ''naming'' of files (via [[directory|directories]]), and indicating ''where'' the files are stored, FAT file systems to some extent merge these two - again, like earlier file systems. The directory entry of a file indicates which cluster is the first cluster of the file; from there, FAT elements form a [[linked list]] of all the clusters in the file.
+Unlike the [[UNIX file system]], which strictly separates the functions of the ''naming'' of files (via [[directory|directories]]), and indicating ''where'' the files are stored, FAT file systems to some extent merge these two - again, like earlier file systems. The directory entry of a file indicates which cluster is the first cluster of the file; from there, FAT elements form a [[list|linked list]] of all the clusters in the file.
 Like the UNIX file system, in the FAT file system, most directories are stored in what are effectively files; the FAT root directory is a special case, and is stored in a specially allocated area at the start of the disk.

@@ Line 7: / Line 7: @@
 Unlike the [[UNIX file system]], which strictly separates the functions of the ''naming'' of files (via [[directory|directories]]), and indicating ''where'' the files are stored, FAT file systems to some extent merge these two - again, like earlier file systems. The directory entry of a file indicates which cluster is the first cluster of the file; from there, FAT elements form a [[linked list]] of all the clusters in the file.
-Like the UNIX file system, most directories are stored in what are effectively files; the root directory is a special case, and is stored in a specially allocated area at the start of the disk.
+Like the UNIX file system, in the FAT file system, most directories are stored in what are effectively files; the FAT root directory is a special case, and is stored in a specially allocated area at the start of the disk.
 ==File names==

← Older revision		Revision as of 13:19, 23 January 2023
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−	The '''File Allocation Table file systems''' (usually abbreviated to '''FAT''') are the name of a group of related [[file system]]s used in [[MS-DOS]] and early [[Microsoft Windows\|Windows]] [[operating system]]s. The first was '''FAT12''' (used by [[floppy disk]]s), from which descended '''FAT16''' and '''FAT32''' (the last used by only by [[hard disk]]s).	+	The '''File Allocation Table file systems''' (usually abbreviated to '''FAT''') are the name of a group of related [[file system]]s used in [[MS-DOS]] and early [[Microsoft Windows\|Windows]] [[operating system]]s. The first was '''FAT12''' (used by [[floppy disk]]s), from which descended '''FAT16''' and '''FAT32''' (the last used only by [[hard disk]]s).

	The name comes from the way they indicate which [[disk block]]s of the [[disk]] are used by any given [[file]], and which blocks are free and available for use - the 'file allocation table'. The disk contains, at the start of the disk, a large [[array]] of entries, one for each 'cluster' (group of blocks) of the disk; each entry indicates whether that cluster is free (and thus available for allocation), or part of a file. (For robustness, there are two identical copies of the FAT.) (FAT file systems were not the first to use this approach; others OS's, such as [[Incompatible Timesharing System\|ITS]], had used a similar approach long before.)		The name comes from the way they indicate which [[disk block]]s of the [[disk]] are used by any given [[file]], and which blocks are free and available for use - the 'file allocation table'. The disk contains, at the start of the disk, a large [[array]] of entries, one for each 'cluster' (group of blocks) of the disk; each entry indicates whether that cluster is free (and thus available for allocation), or part of a file. (For robustness, there are two identical copies of the FAT.) (FAT file systems were not the first to use this approach; others OS's, such as [[Incompatible Timesharing System\|ITS]], had used a similar approach long before.)

@@ Line 1: / Line 1: @@
-The '''File Allocation Table''' (usually abbreviated to '''FAT''') if the name of a group of related [[file system]]s used in [[MS-DOS]] and early [[Microsoft Windows|Windows]] [[operating system]]s. The first was '''FAT12''' (used by [[floppy disk]]s), from which descended '''FAT16''' and '''FAT32''' (the last used by only by [[hard disk]]s).
+The '''File Allocation Table file systems''' (usually abbreviated to '''FAT''') are the name of a group of related [[file system]]s used in [[MS-DOS]] and early [[Microsoft Windows|Windows]] [[operating system]]s. The first was '''FAT12''' (used by [[floppy disk]]s), from which descended '''FAT16''' and '''FAT32''' (the last used by only by [[hard disk]]s).
-The name comes from the way they indicate which [[disk block]]s of the [[disk]] are used by any given [[file]], and which blocks are free and available for use - the 'file allocation table'. (FAT file systems were not the first to use this approach; others OS's, such as [[Incompatible Timesharing System|ITS]], had used a similar approach long before.) The disk contains, at the start of the disk, a large [[array]] of entries, one for each 'cluster' (group of blocks) of the disk; each entry indicates whether that cluster is free (and thus available for allocation), or part of a file. For clusters which are part of a file, their entries in the FAT are used to tie them together. (For robustness, there are two identical copies of the FAT.)
+The name comes from the way they indicate which [[disk block]]s of the [[disk]] are used by any given [[file]], and which blocks are free and available for use - the 'file allocation table'. The disk contains, at the start of the disk, a large [[array]] of entries, one for each 'cluster' (group of blocks) of the disk; each entry indicates whether that cluster is free (and thus available for allocation), or part of a file. (For robustness, there are two identical copies of the FAT.) (FAT file systems were not the first to use this approach; others OS's, such as [[Incompatible Timesharing System|ITS]], had used a similar approach long before.)
-The array elements are of size 12, 16 and 32 bits in FAT12, FAT16 and FAT32 file systems. FAT32 was a relatively late addition; it was added in [[Windows 95]] OSR 2.
+For clusters which are part of a file, their entries in the FAT are used to tie them together. The array elements are of size 12, 16 and 32 bits in FAT12, FAT16 and FAT32 file systems. FAT32 was a relatively late addition; it was added in [[Windows 95]] OSR 2.
 Unlike the [[UNIX file system]], which strictly separates the functions of the ''naming'' of files (via [[directory|directories]]), and indicating ''where'' the files are stored, FAT file systems to some extent merge these two - again, like earlier file systems. The directory entry of a file indicates which cluster is the first cluster of the file; from there, FAT elements form a [[linked list]] of all the clusters in the file.
-Like the Unix file system, most directories are stored in what are effectively files; the root directory is a special case, and is stored in a specially allocated area at the start of the disk.
+Like the UNIX file system, most directories are stored in what are effectively files; the root directory is a special case, and is stored in a specially allocated area at the start of the disk.
 {{semi-stub}}
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 * [https://learn.microsoft.com/en-US/windows/win32/fileio/exfat-specification exFAT file system specification] - also covers FAT12, FAT16 and FAR32
 * [https://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html The FAT filesystem]
 [[Category: File Systems]]
 [[Category: Microsoft Operating Systems]]

← Older revision	Revision as of 17:50, 21 January 2023
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← Older revision	Revision as of 15:49, 21 January 2023
(No difference)