Today

Command line interface (or CLI) operating systems can operate using only the keyboard for
input. Modern OS's use a mouse for input with a graphical user interface (GUI) sometimes
implemented as a shell. The appropriate OS may depend on the hardware architecture, specifically
the CPU, with only Linux and BSD running on almost any CPU. Windows NT has been ported to
other CPUs, most notably the Alpha, but not many. Since the early 1990s the choice for personal
computers has been largely limited to the Microsoft Windows family and the Unix-like family, of
which Linux and Mac OS X are becoming the major choices. Mainframe computers and embedded
systems use a variety of different operating systems, many with no direct connection to Windows or
Unix, but typically more similar to Unix than Windows.

• Personal computers
o IBM PC compatible - Microsoft Windows and smaller Unix-variants (like Linux and
BSD)
o Apple Macintosh - Mac OS X, Windows, Linux and BSD
• Mainframes - A number of unique OS's, sometimes Linux and other Unix variants.
• Embedded systems - a variety of dedicated OS's, and limited versions of Linux or other OS's