Can you explain the evolution hierarchy of operating systems (Linux and Windows) from Unix?


4 Answers 4


This is a highly simplified history of Unix and its derivatives. Windows does not figure in it because its history is essentially separate.

Once upon a time operating systems were complex and unwieldy. One day in the late 1960s, Ken Thompson, Dennis Ritchie and a few of their colleagues at AT&T Bell Labs decided to write a simpler version of Multics to run games on their PDP-7, and thus Unix was born.

AT&T held the rights to the code, and licenses were expensive. Many other companies sublicensed Unix and sold their own version. Major players included DEC, HP, IBM, Sun. Unix variants added their own extensions, often nicking ideas from each other and from academia.

Meanwhile, in Berkeley, a number of academics were unhappy with the licensing situation and decided to create a version of Unix that didn't include any AT&T-licensed code. Thus in the early 1980s the Berkeley Software Distribution, or BSD, became a free variant of Unix. BSD first ran on Minicomputers such as PDP-11 and VAXen.

Meanwhile, on the East coast, Richard Stallman threw a fit when he couldn't get the source code to his printer driver. He founded the GNU (GNU's not Unix) project in 1983 intending to make a free Unix-like operating system, only better. After a little hesitation, the kernel of this operating system was chosen to be Hurd, which is going to be usable any decade now. Many components of the GNU project are included in all current free unices, in particular the compiler GCC.

Meanwhile, in Finland, Linus Torvalds went on a hacking binge in summer 1991. When he woke up, he realized that he'd written an operating system for his PC, and he decided to share it by putting it on an FTP server in a directory called linux. The success exceeded his expectations.

Many people created software distributions including the Linux kernel, many GNU programs, the X Window System, and other free software. These distributions (Slackware, Debian, Red Hat, SUSE, Gentoo, Ubuntu, etc.) are what people generally refer to when they say “Linux”. Most Linux distributions consist mostly of free-as-in-speech software, though software that is merely free-as-in-beer is often included when no free equivalent exists.

Other currently existing unices include the various forks of BSD (you get a choice of FreeBSD, NetBSD and OpenBSD, all being free, open and developed through the 'net), as well as a disminishing number of commercial variants targeted towards servers: and AIX, HP-UX, Solaris, and a few very minor contenders. Another proprietary unix-based operating system is Mac OS X running on Apple desktops, laptops and PDAs.

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    For “free-as-in-speech”, see Wikipedia:Free software — the idea is that you can do what you want with the software. “Free-as-in-beer” means not-costing-money. (English unfortunately uses the same word for the two concepts.) The name GNU/Linux is used for what is most commonly called Linux because a lot of the software in ”Linux” distribution comes from the GNU project or from people inspired by it. Oct 17, 2010 at 18:09
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    Software that you don't need to pay for is “free-as-in-beer”. Software that is “free-as-in-speech” gives you more permissions: you are allowed to redistribute it and to modify it. (These expressions come from the English idioms “free beer” and “free speech”.) I'm afraid I don't know how to explain better, but the Wikipedia article should answer your question. Oct 17, 2010 at 18:52
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    "which is going to be usable any decade now" gave me good chuckles:)
    – Stann
    Apr 19, 2011 at 8:27
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    This essay might be worth mentioning in this context
    – Seamus
    Dec 3, 2011 at 14:10
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    @Abdul BSD originally made code that required the ATT code. Then they decided to replace the ATT parts by non-ATT parts. So today BSD doesn't include any ATT code. In BSD, the original ATT Unix codebase has been removed. Jul 14, 2016 at 12:39

Gilles explained very well the evolution from piece to another here, so I will cover the topic from more broad perspective and give some hints for further research.

From Bazaars and Research Labs to Closed Blobs and Market-marginalized Groups that I think are not that marginal at all

The key term to play with evolution is power. If you are dependent on an OS, for example in the form of security updates, you are dependent on the software-manufacturer and hence it has power over you. It can decide to stop publishing security updates or do any evil that its license allows it to do. If the OS is closed, the users must feel helpless because they cannot fix problems on their own, perhaps shown in hypocriticical feelings such as again the damn driver broken, XYZ's fault. In the latter discussion, you can s,OS,sofware,g and it does not really lose its meaning about power-relationship, clearly some thing being timeless.

I won't reinvent the damn wheel so please read about Bazaars, corporations and social-environmental-and-other problems below.


  1. Homebrew computer club before Apple and such things when things were open.
  2. Computer History Museum covers a lot of good things here.
  3. "Homestead High School Electronics Club, Cupertino, California" about Apple's founding member here.

Ending, Now and Still Evolving

  1. Amos Batto's essay explaining some reasons behind closing things (Internet Archieve article, cannot be found from Google easily)
  2. For visualizing the evolution, please, see the picture below from Wikipedia where things started from Bazaar (orange phase) and ended to red-green phase where things are still evolving or even chaotic. The picture is wrong or pro-Minix-advertising in some points, n.b. comments. Please, read about the Minix-Linux -turning point and differentiate the marketing free, free-as-beer and free-as-speech -- the debate here. Shortly, Minix was not free-as-free-speech and Tanenbaum made money with it while Linus offered his OS with less restrictive license, very important years to understand so do not get misguided by some oddities in the picture. This crucial point later affected separate parties such as FreeBSD, Linux and Mimix -formation to their current form. Please, note that I don't call them with cohesive terms such as "open-source" because the term is getting misused.

  3. When I used the term bazaar in the title, I really meant it. It is to some extent chaotic so it is hard to get a large picture but then again there are some very systematic groups. The one who can offer the most appropriate solution to current problem will get awarded and can sell his/her products on the market. Sometimes, a developer beats a huge 100 heads' dev teams and sometimes contrary. Torvards have drawn a good analogy with closed blob and open code (or equivalent in some email) to the science and alchemy. I think his point was that while alchemists are extinct in science, you can still find them in Software -area. He did not explain it much but my idea is that alchemists today exist in software engineering because it can be useful time-to-time, some practical situations require creative solutions. It is a bit like physicists used the sirac-delta-distribution over about 30years (according to my lecturer) before mathematicians agreed that it could be formulated in Mathematics, this phase may take some time. But do not underestimate the speculative frenzy in human instincts, it is surprising how many times I have seen people writing something "new", finding it was already invented. Welcome back to the bazaar!

Culture, Money and Intellectual Capital

  1. The FOSS movement is not a marginal body, please, note that they do have their own things such as music (here or here)and more-and-more hardware (here) -- if your media says something else or nothing, they are ignoramuses. The movement is more like a culture -- so the term movement is rather misleading -- with their own slants, habits and even past-times, perhaps hard to grasp the idea but more I get into it, the more I think it is but beware wanna-be-users -- it does no good get involved into meaningless debates about free and closed if the terms are not well-defined or documented like here.
  2. I often find it stupid that people compare this decentralized thing to certain bureaucratic firms, not all of them, because the goal of many innovators per se is many time to have fun instead to create money. So the question like "do they get paid?" is a bit arrogant, did you get paid to be a roman or do you now get paid to be XYZ-citizen? Probably not or perhaps -- with a successful endeavor -- you need to wisely choose your camp as always. There are however other important things, such as knowledge, responsibility and co-operation, sometimes hard to measure in $. Is it actually called IC with business people? If so, you may get important skills by engaging to some project, an asset highly appreciated with knowledgeable firms -- but again seen too much wanna-be-reinventing-the-wheel-code so do good research before getting too much involved.

  3. If you want to know how to get "paid" with this field. I would suggest to research about risk-reward -relationship, perhaps in Money.SO. The unix tools are like science, they are very liberal and allow you to do many things. It depends on the user whether you get paid or not. I think to get paid you need to get into some risky projects like time-consuming/hard/ignored. There is no easy way to get paid anywhere. Why would there be? If there was an easy way, the markets were not efficient. The reason why some big corps get paid is that they have taken huge risks and loans and now get rewarded, sometimes their actions are evil and they may get punished. But for an individual, I suggest a slow steady advancing. To understand why think about unix's early history about research labs, a lot of slow monotone working and prototyping.

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Want to know more?

Your questions have too many confusions to attack them easily, such as presupposition about hierarchy that ignores the idea about chaos and ambiguous terms such as Windows -- dev branch or branding? And the term from Unix in the title tastes too much appealing-to-populism-in-Unix-quesion-site. It is hard to say how /dev/null such as W. and other closed things evolved because we don't know them, except speculation! People who know cannot speak. The source is primary, the rest is secondary. Be sure which blindfolds, i.e. search engine, you use for this topic, many valuable articles are dumped with irrelevant information as the case with the above removed article. As a starting point, you could try some links offered above or below.

  1. Why are the open source business people not ultra rich yet?

  2. Where Are All the Open Source Billionaires?

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    Whoever made that chart was inaccurate about Minix. It wasn't open source, at least by the OSI definition. Mar 30, 2011 at 15:51
  • @Faheem Mitha: excellent observation, it is actually a crucial point in the whole software history! Mimix was not free when Torvalds started Linux (actually I think Torvards has said that if Mimix-or-some-was-it-bsd-distro (time when corps noticed the competitive edge with software, closed blob coming) had been free, he would not have developed Linux. Anyway good point, the picture should be corrected. Wikipedia about Mimxi 'starting with version 3, MINIX was free and redesigned for “serious” use.'. +1
    – user2362
    Mar 30, 2011 at 16:09
  • @hhh: Right, AT freed Minix later on. I don't see the words you quote on the Minix Wikipedia page though. It just says it was freed April 2000, but doesn't say what version. Mar 30, 2011 at 16:52
  • @Faheem Mitha: sorry for not pasting url (space lim) but here it is[1]. I notified in the body to these comments, thank you. It does not however make it clear which year the license of Mimix was changed. I had a faint memory that it was earlier but have to dig for some source code to verify it. [1] en.wikipedia.org/wiki/Linux#MINIX
    – user2362
    Mar 30, 2011 at 16:58
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    @hhh: Yes, I see those words in the Linux page. Funny, the Minix page only has the freeing date, and the Linux page only has the first freed version! I'm not sure what you mean by "notified in the body to these comments", though. Mar 30, 2011 at 17:28

Renjith, there is no "root" operating system. History of operating systems is pretty long. I'd just recommend you to read next articles on Wikipedia:

Have fun, it's really interesting stuff...

  • OK.Any other short explanations?
    – Renjith G
    Oct 16, 2010 at 21:08

For a really crazy diagram of the evolution of UNIX, see here. Not that it's very useful, though :).

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