Is there actually a requirement to call something an OS or can I just make a program that opens in fullscreen, has a log-in, and does random things like "luanch" games and websites?
I hope we're talking about Operating Systems, I wouldn't know anything else OS would stand for.

An operating system is that which can run in and of itself, on a piece of hardware. Vista is an OS (not Windows itself), as are Ubuntu (not Linux itself) and Snow Leopard (so, not Mac itself).

They get planted on a hard drive with a connected processing unit to make a computer. The HD and CPU are typically made by someone like Dell, Hewlett Packard, or Apple.

However, a program that requires another OS is not an OS. It may be a virtual OS, or a simulator, but it isn't a true OS.

Well, thats what I ment - a virtual OS made with GameMaker. You can basically make anything and just claim it to be an OS. It would kind of pointless unless you actually made it in depth and it offered some kind of convenience that the running OS did't have to offer.

If I could guess what some requirements for an OS would be I would say:
-file navigation/managment system
-and...well, that's all I can really think of.
Yet I wouldn't even qualify just that as an OS. I guess it's all in how it would be used.

Uh... well, I'm pretty sure this sub-forum is about actual Operating Systems. Luke, for instance, was (is?) developing an Operating System that did not rely on any Windows, Linux or Mac.

Yeah, it incorporated all three of those OS's. Long-lost project though. It would only work on my Dell D800 laptop >.<

This board is for anything OS, so this thread is cool with me.

Exactly. Even if it's virtual OS's. I'd actually be pretty interested in seeing some people's home made OS's.

That's a little above my paygrade. ($0)