Editing File Allocation Table (section)

{{Short description|File system used for MS-DOS, Windows9X and other PCs}}
{{further|Design of the FAT file system}}

{{Use mdy dates|date=April 2016|cs1-dates=y}}
{{Use American English|date=July 2018}}
{{Anchor|FASTFAT}}<!-- for parked anchors -->
{{Infobox file system
| name = FAT
| image = 
| developer = [[Microsoft]]<!-- original FAT, FAT16, FAT32 -->, [[NCR Corporation|NCR]], [[Seattle Computer Products|SCP]]<!-- FAT12 -->, [[IBM]], [[Compaq]]<!-- Compaq MS-DOS 3.31-->, [[Digital Research]]<!-- lots of extensions -->, [[Novell]]<!-- lots of extensions continuing the DRI line of products -->, [[Caldera (company)|Caldera]]
| full_name = File Allocation Table
| variants = 8-bit FAT, [[#FAT12|FAT12]], [[#FAT16|FAT16]], [[#FAT16B|FAT16B]], [[#FAT32|FAT32]], [[exFAT]], [[#FATX|FATX]], [[#FAT+|FAT+]]
| introduction_date = {{Start date|1977}}
| introduction_os = [[Standalone Disk BASIC-80]]
| partition_id = [[Master Boot Record|MBR]]/[[Extended Boot Record|EBR]]:{{ubli
 | FAT12:&nbsp;<code>{{abbr|0x|Values in C-notation for hexadecimal numbers}}[[Partition type#PID_01h|01]]</code> e.a. (Extended Attribute)
 | FAT16:&nbsp;<code>{{abbr|0x|Values in C-notation for hexadecimal numbers}}[[Partition type#PID_04h|04]]</code><code>[[Partition type#PID_06h|0x06]]</code><code>[[Partition type#PID 0Eh|0x0E]]</code> e.a.
 | FAT32:&nbsp;<code>{{abbr|0x|Values in C-notation for hexadecimal numbers<span id="FAT32X"></span>}}[[Partition type#PID_0Bh|0B]]</code><code>[[Partition type#PID_0Ch|0x0C]]</code> e.a.
 | [[Basic data partition|BDP]]: <code>EBD0A0A2-B9E5-4433-87C0-68B6B72699C7</code>
 }}
| directory_struct = Table
| file_struct = [[Linked list]]
| bad_blocks_struct = Cluster tagging
| max_file_size = 4,294,967,295 bytes (4&nbsp;[[gigabyte|GB]] − 1)<!-- 2^32 − 1 --> with FAT16B and FAT32<ref name="GB4" />
| max_files_no = {{ubli
 | FAT12: 4,068 for 8&nbsp;[[kilobyte|KB]] clusters <!-- 2^12 − 12 (reserved clusters) − 16 (number of 8&nbsp;KB clusters for directory entries) -->
 | FAT16: 65,460 for 32&nbsp;KB clusters <!-- 2^16 − 12 (reserved clusters) − 64 (number of 32&nbsp;KB clusters for directory entries) -->
 | FAT32: 268,173,300 for 32&nbsp;KB clusters <!-- 2^28 − 12 (reserved clusters) − 262144 (number of 32&nbsp;KB clusters for directory entries) -->
 }}
| max_filename_size = [[8.3 filename]], or 255 [[UCS-2]] characters when using [[Long filename|LFN]]<ref group="nb" name="NB_LFN_UNI">Since [[Windows 2000]], Microsoft Windows uses [[UTF-16]] instead of [[UCS-2]] for the [[Unicode in Microsoft Windows|internal "Unicode"]]. In UTF-16, a "character" (code point) may take up two code units.</ref>
| max_volume_size = {{ubli
 | FAT12: 32&nbsp;[[megabyte|MB]]<!-- with 2^16 sectors á 512 bytes, or with 8&nbsp;KB clusters --> (256&nbsp;MB for 64&nbsp;KB clusters<!-- and EBPB -->)
 | FAT16: 2&nbsp;GB (4&nbsp;GB for 64&nbsp;KB clusters)
 | FAT32: 2&nbsp;[[terabyte|TB]] (16&nbsp;TB for [[4Kn|4 KB sectors]])
 }}
| dates_recorded = {{ubli
 | Modified date/time, creation date/time (DOS&nbsp;7.0 and higher only),
 | access date (only available with [[ACCDATE (CONFIG.SYS directive)|ACCDATE]] enabled),<ref name="Microsoft_2006_ACCDATE" />
 | deletion date/time (only with DELWATCH 2<!-- with Novell DOS 7, Caldera OpenDOS 7.01, DR-DOS 7.02 and higher -->)
 }}
| date_range = [[Epoch of 1980-01-01|1980-01-01]] to [[Year 2100 problem|2099-12-31]] ([[Year 2108 problem|2107-12-31]])
| date_resolution = {{ubli
 | 2&nbsp;seconds for last modified time,
 | 2&nbsp;seconds for creation time,
 | 1&nbsp;day for access date,
 | 2&nbsp;seconds for deletion time
 }}
| forks_streams = Not natively
| attributes = [[FAT file attributes|Read-only, hidden, system, volume, directory, archive]]
| file_system_permissions = {{ubli
 | FAT12/FAT16: File, directory and volume access rights for [[FAT file access rights|read]], [[FAT file access rights|write]], [[FAT file access rights|execute]], [[FAT file access rights|delete]] only with [[DR-DOS]], [[PalmDOS]], [[Novell DOS]], [[OpenDOS]], [[FlexOS]], [[IBM 4680 OS|4680&nbsp;OS]], [[IBM 4690 OS|4690&nbsp;OS]], [[Concurrent DOS]], [[Multiuser DOS]], [[Datapac System Manager|System Manager]], [[REAL/32]]: {{ubli
  | execute with only FlexOS, 4680&nbsp;OS, 4690&nbsp;OS;
  | individual file / directory passwords not with FlexOS, 4680&nbsp;OS, 4690&nbsp;OS;<!-- at least I could not find any user or programmer's documentation for it so far -->
  | [[FAT file access rights|world/group/owner]] permission classes only with multiuser security loaded
  }}
 | FAT32: Partial, only with DR-DOS, REAL/32 and 4690 OS<!-- version 2 and higher -->
 }}
| compression = {{ubli
 | FAT12/FAT16: Per-volume, [[SuperStor]], [[Stacker (disk compression)|Stacker]], [[DoubleSpace]], [[DriveSpace]]
 | FAT32: No
 }}
| encryption = {{ubli
 | FAT12/FAT16: Per-volume only with [[DR-DOS]]
 | FAT32: No
 }}
| data_deduplication = 
| copy_on_write = 
| OS = 
}}

'''File Allocation Table''' ('''FAT''') is a [[file system]] developed for personal computers and was the default file system for the [[MS-DOS]] and [[Windows 9x]] operating systems.{{cn|date=September 2024}} Originally developed in 1977 for use on [[floppy disk]]s, it was adapted for use on [[Hard disk drive|hard disks]] and other devices. The increase in disk drive capacity over time drove modifications to the design that resulted in versions: [[#FAT12|FAT12]], [[#FAT16|FAT16]], [[#FAT32|FAT32]], and [[exFAT]]. FAT was replaced with [[NTFS]] as the default file system on Microsoft operating systems starting with [[Windows XP]].<ref>{{cite web |url=https://windows.microsoft.com/en-us/windows-vista/comparing-ntfs-and-fat-file-systems |title=Comparing NTFS and FAT file systems |publisher=Microsoft |access-date=2014-01-27 |archive-date=2016-06-20  |archive-url=https://web.archive.org/web/20160620004455/http://windows.microsoft.com/en-US/windows-vista/Comparing-NTFS-and-FAT-file-systems |url-status=live }}</ref> Nevertheless, FAT continues to be commonly used on relatively small capacity [[solid-state storage]] technologies such as [[SD card]], [[MultiMediaCard]] (MMC) and [[eMMC]] because of its compatibility and ease of implementation.<ref>{{Cite web |title=A brief introduction to FAT (File Allocation Table) formats |url=http://www.wizcode.com/articles/comments/a-brief-introduction-to-fat-file-allocation-table/ |url-status=dead |archive-url=https://web.archive.org/web/20150925082826/http://www.wizcode.com/articles/comments/a-brief-introduction-to-fat-file-allocation-table/ |archive-date=September 25, 2015 |access-date=2015-09-24 |website=www.wizcode.com |df=mdy-all}}</ref>