Editing File Allocation Table (section)

=== <span id="EA"></span>Extended attributes ===

[[OS/2]] heavily depends on [[extended attribute]]s (EAs) and stores them in a hidden file called "<code>EA&#x2420;DATA.&#x2420;SF</code>"<!-- Since the exact spelling is important and most sources list only 10 of the 8+3 available characters in directory entries, recheck the exact 8+3 byte spelling of this filename --> in the [[root directory]] of the [[#FAT12|FAT12]] or [[#FAT16|FAT16]] volume. This file is indexed by two previously reserved bytes in the file's (or directory's) [[FAT directory entry|directory entry]] at offset [[Design of the FAT file system#DIR OFS 14h|<code>0x14</code>]].<ref name="Eager_2000_EA" /> In the [[#FAT32|FAT32]] format, these bytes hold the upper 16&nbsp;bits of the starting cluster number of the file or directory, hence making it impossible to store [[OS/2 EA]]s on FAT32 using this method.

However, the third-party FAT32 [[installable file system]] (IFS) driver FAT32.IFS version 0.70 and higher by Henk Kelder & Netlabs for OS/2, [[eComStation]] and [[ArcaOS]] stores extended attributes in extra files with filenames having the string "<code>&#x2420;EA.&#x2420;SF</code>" appended to the regular filename of the file to which they belong. The driver also utilizes the byte at offset [[Design of the FAT file system#DIR OFS 0Ch|<code>0x0C</code>]] in directory entries to store a special mark byte indicating the presence of extended attributes to help speed up things.<ref name="Kelder_2003_FAT32IFS0913" /><ref name="Kelder_FAT32IFS074" /> (This extension is critically incompatible with the FAT32+ method to store files larger than 4&nbsp;GB minus 1 on FAT32 volumes.)<ref name="DRDOS_FAT+_R2" />

Extended attributes are accessible via the [[Workplace Shell]] desktop, through [[REXX]] scripts, and many system [[graphical user interface|GUI]] and [[command line interface|command-line]] utilities (such as [[4OS2]]).<ref name="Eager_2000_Tavi" />

To accommodate its [[OS/2]] subsystem, [[Windows NT]] supports the handling of extended attributes in [[High Performance File System|HPFS]], [[NTFS]], FAT12 and FAT16. It stores EAs on FAT12, FAT16 and HPFS using exactly the same scheme as OS/2, but does not support any other kind of [[Alternate Data Streams|ADS]] as held on NTFS volumes. Trying to copy a file with any ADS other than EAs from an NTFS volume to a FAT or HPFS volume gives a warning message with the names of the ADSs that will be lost. It does not support the FAT32.IFS method to store EAs on FAT32 volumes.

[[Windows 2000]] onward acts exactly as Windows NT, except that it ignores EAs when copying to FAT32 without any warning (but shows the warning for other ADSs, like "Macintosh Finder Info" and "Macintosh Resource Fork").

[[Cygwin]] uses "<code>EA&#x2420;DATA.&#x2420;SF</code>" files as well.