What is the plural of OS (Operating System)?

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(updated 20141020CE)
To my dislike, I have come to the conclusion that it is OSs, and that some are also making use of OS as plural too.  Yes, one can see how OSs could get confused with other abbreviations that are OSS.

The below will break down the various considerations based on the Amglish (American English/US language/American language), and English language (British English/England language). :) 

• OS = Operating System (Example Sentences = Microsoft Windows XP is an operating system.  Microsoft Windows XP is an OS.  This operating system is not free.  This OS is not free.)
  
  
• OS = Operating Systems (Example Sentences = These operating systems are free.  These OS are free.).  This is not the preferred usage.
  
  
• OS's = Operating System's (Example Sentence = This is the operating system's core code.  This is the OS's core code.)
  
  
• OSs = Operating Systems (Example Sentence = There are many operating systems in the world; such as DOS, Atari, Macintosh, Unix, Centos, Windows 8, and many dozens more, if not hundreds.  There are many OSs in the world.)
  
  
• OSs' = Operating Systems' (Example Sentence = These operating systems' cores run at 8GHz due to parallel operation channels.  These OSs' cores run at 8GHz due to parallel operation channels.)
  
  
• OS' = Operating Systems' (Example Sentence = These operating systems' cores run at 8GHz due to parallel operation channels.  These OS' cores run at 8GHz due to parallel operation channels.).  Only happens when OS is used/seen as a plural form too, but preferred or should be using OSs'.
  
  
• OSes = Simply wrong.  Expanded, this would become Operating Systemes, and that is wrong spelling.

I would have much more preferred it if it was OSes, but it just is not correct, even though I have seen some British folks make use of OSes.  As I recall, the reason confusion occurs with usage of OSes is because there are other phrases that also have the abbreviation of OS used for them, but one or more of those have plurals that end with es.  I saw one phrase that OSes may have been correct for, and, again, that is because the other phrase's plural gets added es to show it is plural, and so OSes made sense for only that phrase.  It is incorrect to use it for Operating Systems.

OS's references something belonging to a single operating system.

OSs would correctly reflect proper grammar for a plural abbreviation of operating systems.  Know that you will find OS being used as a plural form too; such as "some of these OS are no longer being supported".  Based on the above logic, it is preferred to be "some of these OSs are no longer being supported".

OSs' references something associated with or belonging to a group of operating systems.

OS' references something associated with or belonging to a group of operating systems.  This happens only when OS is used as a plural representation, and it is preferred to be OSs' to quickly and easily distinguish singular and plural uses of OS.  It helps a lot when searching.  When OS is used as both a singular and plural representation, it becomes harder, and searches are more difficult. 

In case someone is actually considering OS'es, then know that this is very wrong in my belief.  OS'es = Operating System'es.  Does not make sense.  OS is not a stand alone word, but an abbreviation (specifically an initialism).  If there was such a word as Os, then ya, Oses may be a correct spelling, but the abbreviation in consideration here is OS, and it is not the same as a word of os or name or Os. 

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