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Computer Science Links

Operating Systems

This is my non-comprehensive and incomprehensible list of various computer operating systems. Not to be taken internally. Use only under the advice of a physician.

Quick links

This is a big page. Here are a few quick jumps to major sections.


First, here are the Unix-type general-purpose OSen.

  • For starters, what could possible come ahead of The BSD OS Family, including
    • FreeBSD, which targets x86 and is my PERSONAL favorite
    • NetBSD, the most portable OS on the planet
    • OpenBSD, which concentrates on security
    • BSDi, which makes a commercial version of BSD
  • Linux is the new buzzword among free OSen. You can also find a lot of Linux info at or at Lots of people seem to like Linux, even if I personally aren't very fond of it. But hey, if it works for you, what more can you ask? There is an unending list of Linux distributions, some of which can be found here (a smaller list of the more 'real' ones), as well as one at linuxhq and another at LinuxLinks. If anyone has a more comprehensive list, please email it to me!! The 4 major (IMO, of course) distributors of Linux are
    • Red Hat (the pretty boy of Linux dists),
    • Debian (a 'simpler' dist than Red Hat, if less prettified),
    • Slackware (the hacker's choice), and
    • SuSE (which seems to also have a large following).
  • Solaris is the OS designed by Sun Microsystems for their well-known SPARC platform. Solaris is a rather quirky OS, but then, all OSen are quirky in their own little ways, aren't they? Solaris is a renaming (and re-numbering, even of itself lately) of SunOS, Sun's earlier OS, which was a lot saner (if not as full-featured as Solaris is these days).
  • Tru64 is Compaq's name for the OS they support which runs on their RISC platform, which used to be the DEC Alpha (Compaq now owns DEC). Yes, this is the same OS that used to be called Digital Unix, and DEC UNIX, and OSF/1, and Ultrix, and occasionally (and incorrectly) DG/UX, and was derived pretty straightforwardly from Mach, and... (ad infinitum).
  • HP/UX is (go ahead, guess) the OS developed by HP for their HP 9000 servers, which are based on the PA-RISC processor architecture.
  • IBM also puts out a UNIX-ish OS for their RS/6000 series computers, called AIX, whose name can be mis-appropriated to form many interesting (and apt) nicknames, such as "Ain't unIX" and "Aches".
  • The Santa Cruz Operation, also known simply as 'SCO', makes a UNIX-derived OS. That's all we'll say about that.
  • IRIX is the OS developed by SGI (do they still allow themselves to be called SILICON GRAPHICS? Whoops, I just did it anyway...) for their various servers. SGI does some neat stuff :)
  • UNICOS, and its partner UNICOS/mk, is the OS run by Cray on their line of supercomputers. When God wants a computer, he calls Cray. This would be where you go to get the most powerful computers in the world.
  • CMost is the OS used by Connection Machines on their supercomputers, which are also on that mythical top tier with Cray. They don't seem to give much information about their systems on their website, though...
  • MINIX is a UNIX clone designed pretty much for the purpose of showing how an OS can be designed. It provided the basis and impetus for Linux to be originally written, and it's completely freely available to everyone. Here is another good page of MINIX information.

"Microcomputers? How passe!"

The microcomputer 'revolution' (for lack of a more useful word for it) has created a class of OSen unto itself.

  • Much as it galls many of us to admit it, no OS list is really complete without including Windows, and the infamous company behind it, Microsoft. Ugh. I just won't say any more there, consider yourself lucky I deigned to include it.
  • However, I do offer up OS/2 Warp to throw in the face of Windows. It may seem dead, kids, but you'd be surprised how many places and applications still use OS/2 to this day.
  • BeOS is one of the new kids on the block of PC OSen. Despite having less market penetration than most, it's a very well-designed and well-implemented OS.
  • DOS is the old familiar OS to people who remember the 80's, and the ancient piece of crap the Windows weenies these days put down without understanding. And yes, Virginia, there ARE still people using DOS. Whoever it is that runs has some cool DOS-type stuff here.
    • FreeDOS is a project to develop a complete freely-available version of DOS (MS-DOS compatible). Neat.
    • DR-DOS was a popular DOS variant at one time. Hm, their website seems to be in la-la land at the moment.
    • Here's some information on MS-DOS, the DOS put out by Microsoft (which is what most people think of first when they think "DOS", as it's kinda the de-facto standard for what DOS is).
    • PC-DOS was IBM's version of DOS, which it seems possible some people are still using.
    • Though this could also be listed in the embedded systems category, we'll mention Datalight's ROM-DOS, which is designed to be run in small embedded systems.
    • RxDOS is Yet Another DOS Clone in development. You may find more information (or not, really) on their main SourceForge page.
  • CP/M is an OS you don't hear much about anymore, but it was at one time the OS that microcomputers ("PC's") were assumed to be running. It was especially popular on the Z80 CPU family.

Help! I'm trapped in a microkernel!

Embedded systems are a fact of life, and they're a lot more widespread than you think. Many of them use cut-down general purpose OSen (did you know that a lot of ATM machines are actually running OS/2? Sick, eh?), but there are some OSen that are specifically targetted at embedded systems.

  • QNX is a OS designed for real-time embedded systems. Very modular, microkernel architecture. Neat stuff.
  • LynuxWorks is a company that does a number of things for embedded/realtime systems, including 'Lynx' (not the web browser), which is similar (at least in concept) to QNX.

Is that a PDA in your pocket, or are you just happy to see me?

PDA's are the big hype nowadays. Springing from the wellspring of the early pocket electronic phone and address books, they now sport notepads, email, web browsing, games, clocks, calculators, currency converters, translators, and will soon dry your socks for you.

  • EPOC is the brainchild of Symbian, a company targetting developers in the PDA market.
  • NewtonOS was Apple's OS for their palm-top systems until they cancelled it in 1998 (see their press release for details) and moved everything over to concentrating on using MacOS (though this link only covers OS 9.x, not OS X as well).
  • PalmOS seems to be the emerged standard in PDA OSen. It runs on the majority of the PDA's currently out there, including the Palm series, the Handspring Visor, and others. If you've got a PDA, it's likely to run a variant of PalmOS.
  • Windows CE is the other major player in the PDA market. I'll just be tactful and not say anything else about it, 'K?
  • Research In Motion makes a line of PDA-type items with an emphasis on wireless network access, which seem to use their own little OS.

This needs to be done in 0.3846 +/- .00000008 seconds

Real-time operating systems are an interesting field of study. They aren't really (generally) general-purpose systems, but intended for a specific set of tasks. Their base intention is to handle very time-sensitive things, when it NEEDS to be done in X time, or to not be done at all. You don't trust your life to a multitasking system, you trust it to something that does nothing but watch you.

  • EROS is the Exteremely-Reliable Operating System. Originally implemented at the University of Pennsylvania, it's currently living at Johns Hopkins. Looks kinda neat.
  • RT/Linux is a real-time OS that runs Linux (or, in some varieties, NetBSD) in its 'spare time'. Thus, you get the advantages of a hard real-time OS, but you also have a general purpose OS running as the lowest-priority process.

"IP is a fad. Open standards are for weenies and universities."

Y'know, there was a time when 'Network OSen' were taken seriously, and thought to be a big group at the top echelon of the field. *snort* They do provide good case studies for not keeping up with changing market conditions, at least.

  • Novell makes several products that could be listed here, including NetWare, an OS that for some reason stubbornly refuses to die the death it should have died 10 years ago. Sigh.
  • VINES, aka Banyan, isn't really an OS so much as a set of protocols, but we'll list it here so Novell doesn't get lonely.

I am not a subcategory! I am a FREE OS!

Then there's a bunch of stuff that's pretty much on its own. Doesn't really fit well into any larger categories, and it's no fun to create a bunch of categories with just one entry.

  • OpenVMS is a version of VMS, which was DEC's original operating system for their servers back before UNIX became popular. Some people still use it.
  • Plan 9 is a rather interesting (and rather unknown) OS from the same people who brought you UNIX and C. It's distributed by Vita Nuova Holdings.
  • Inferno is similar to Plan9, targetting more at distributed applications. Like Plan9, it's distributed by Vita Nuova Holdings.
  • AdaOS is a project to write a full OS in Ada, Just Because. Um, yeah. You go guys. We'll be right behind you...
  • Amoeba is an effort to build an OS specifically for distributed and parallel applications. Cool :)
  • Apollo/DOMAIN was a niche (but COOL!) computer system. Unfortunately, it's almost never even mentioned, and even more rarely encountered these days.
  • AtheOS is an OS intended by its designers to be "The New Uber Desktop OS". It'd be easy to dismiss like all the rest except that the damn thing seems to actually be RUNNING. They claim that their webserver is running it. Funky.
  • And of course, we have the (in)famous ITS (Incompatible Timesharing System) in all its glory.
  • Multics, (more information here), was in that group of the first 'real operating systems' in existence. It was one of the primary sources for ideas used by the authors of the first UNIX system, and the very name UNIX was a play on the name Multics. Per this letter, the last Multics system was shut down on October 30, 2000. Indeed the passing of an era.
  • AmigaOS is one of those operating systems that was cool, became obsolete and passe, and just refuses to die.
  • Real/32 is sort of targetted as a Real-Time OS, but I'm putting it here. Logan Industries describes it thusly:

    REAL/32 is a sophisticated, 32-bit, real-time, multi-tasking, multi-user DOS/Windows compatible operating system.

    Phew. What a mouthful. You see why I put it in this category :)
  • RISC OS is an OS designed explicitly for 32-bit RISC chips. It's one of those niche OSen that keeps hanging around. More info is also available here.

Of course, this whole shebang just barely scratches the surface of the total number of operating systems and OS-like entities out there. To compile a full list would be very time-consuming, very difficult, and, in a word, absurd. It would take someone with no grasp on reality to even attempt it.

Fortunately, there's plenty of people like that in the world :]. Here are just a few of the resources I've used in putting together the small list I have.

  • Patrick Bridges has a big-ass list of operating systems. His main homepage is here.
  • Here's another big list at dmoz.
  • have a HUGE list on their truely massive site devoted to just this sort of information. Cool stuff!