Some popular Operating System's are:

* Unix: multi-tasking, multi-processing, multi-user, protected, with built-in support for networking but not graphics.
* Windows NT: multi-tasking, multi-processing, single-user, protected, with built-in support for networking and graphics.
* Windows 95/98: multi-tasking, multi-processing, single-user, unprotected, with built-in support for networking and graphics.
* Windows 3.x: single-tasking, single-processing, single-user, unprotected, with built-in support for graphics but not networking.
* DOS: single-tasking, single-processing, single-user, unprotected with no built-in support for graphics or networking.
* NetWare: multi-tasking, multi-processing, single-user, unprotected, with built-in support for networking but not graphics.

As of 2012:

Windows 7 and Windows 8
Mac OS X
UNIX SVR5
LinuxMint 13
Ubuntu 12
CentOS 6
RHEL 6
Debian 6
Android 4
iOS 6

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