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On old Macs before OS X files already could have two "forks" - a data fork and a resource fork.

According to Wikipedia, at some point the HFS+ filesystem of OS X gained the ability to have an arbitrary number of forks, much like Microsofts "Alternate Data Streams" (ADS).

HFS Plus permits filenames up to 255 UTF-16 characters in length, and n-forked files similar to NTFS, though until recently, almost no systems software takes advantage of forks other than the data fork and resource fork.

I want to know what the official term is for these forks or streams. I guess it's possible they're just called "forks" but that terms has several meanings already in computing. I've done some searching but can't find a definitive answer.

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up vote 3 down vote accepted

Apple uses "multiple fork" or the shortened form "multi-fork" consistently through its documentation, so it seems it is the official term. I list here a few examples:

https://developer.apple.com/library/mac/#documentation/General/Conceptual/SLGlobalGlossary/Glossary/Glossary.html (Last updated: 2010-07-09)

HFS+ Hierarchical File System Plus. The Mac OS Extended file-system format. This format adds support for filenames longer than 31 characters, Unicode representation of file and directory names, and efficient operation on very large disks. HFS+ is a multiple-fork volume format.

https://developer.apple.com/library/mac/#documentation/Porting/Conceptual/PortingUnix/io_porting/io_porting.html (Last updated: 2012-06-11)

(...) some Mac applications also take advantage of the HFS+ file system’s ability to handle multi-forked files.

https://developer.apple.com/library/ios/#documentation/CoreFoundation/Conceptual/CFBundles/AboutBundles/AboutBundles.html (Last updated: 2010-07-08)

Bundles can reside on volumes of many different formats, including multiple fork formats like HFS, HFS+, and AFP, and single-fork formats like UFS, SMB, and NFS.

When talking about "fork" in computing I can only think of either HFS+/HFS forks or the system call for creating a child process.

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What a great answer - thanks for your effort! (-: –  hippietrail Oct 25 '12 at 10:41
You're welcome! –  jaume Oct 25 '12 at 10:41
Yes there is forking child processes and also forking projects, especially open source projects, as happened to OpenOffice->LibreOffice and WikiTravel->WikiVoyage. There may be other uses I don't know of too... –  hippietrail Oct 25 '12 at 10:44
Oh God, I forgot fork in software development, thanks for pointing that out. –  jaume Oct 25 '12 at 13:03
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