People often tend to blur the lines between operating systems, architectures, and processors. All this talk about Macintosh VS "PC"...
Just because you own an Apple Macintosh computer doesn't mean you run MacOS on it. Guess what? Linux, BSD, and various other operating systems run on that architecture. AmigaOS (Hey! Amiga wasn't in that poll...) runs on the 68k, which all macs up until the PowerPC were based on. Of course, the Amiga is a *TOTALLY* different architecture than any home computer we have avalible today. Oh guess what? See that PalmOS device in your pocket? That runs on a DragonBall processor... a "modern" version of the 68k line.
"PC" is a very vauge term! What most people mean when they say "PC" is "IBM-Compatible". This is the predominant architecture for the x86 processor developed by Intel. This architecture runs all kinds of opeating systems... DOS, OS/2, Linux, BSD, Windows, BeOS, not to mention tons of small OSes. Did you know that there are lots of implementations of DOS? It's not just a Microsoft product... FreeDOS, OpenDOS, DrDOS, .... Speaking of BeOS... that was an operating system origanally indended to run on the BeBox, an architecture cerated by Be, Inc. that quiclky died.
No one has mentioned Sun, Next, DEC, or a million other companies.
SPARC, Alpha, MIPS, ARM, ... the list goes on and on and on.
There is really a heck of a lot more to the world of computing than the things that sit on the desks of most people.
Check out the
TUNES OS Review to get somewhat of an idea of how many operating systems are out there.
Of course... there's always the systems like Squeak (SmallTalk-80) that blur the lines between operating system, programming langauge, and applications...
</rant>