What are the different types of operating systems?

What are the different types of Operating System? Can I installl 3 OS in my system by option menthod?

Firstly: There are many types of Operating Systems - the main ones include Windows (Vista, XP, back through to 95 - earlier windows are actually Dos GUI's), Mac OS X (10.0 through to 10.5 (leopard)), all the various varieties of Linux (such as RedHat, Mandrake, Gnoppix, Ubuntu, etc), and the many old OS's of the past, such as Dos, all the old Apple OS's, CP/M, OS/2, RiscOS... the list goes on.

Not all OS's will work on your computer - some need specific types of processor architecture (such as RiscOS, or earlier Apple OS's). In general, all versions of Windows and most Linux versions will work on your computer - OS X will only work on a Mac (yes, there are ways to get it working on a normal PC, but that's illegal, so we won't go there).

Secondly: Yes, you can have 3 OS's onto your computer. More if you want. But it can be a bit tricky, especially if you use older versions of Windows as they don't like other OS's being there. Primarily, what you need is separate partitions for each OS, and a Boot Loader. For Boot Loaders, I like XOSL - very nice to use, and uncomplicated (works best if its on its own separate, albeit small, partition). Just install each OS to the partitions, and put XOSL on and you should be able to get it up and running very easily. You might also want an additional partition which is of a file system type that all the OS's can understand - if you use Windows for one of the OS's that basically that limits you to the Fat32 system (Windows doesn't understand the Linux file system types).

Any further questions, don't hesitate to ask!