1.2 Overview of Computer Operating Systems
1.2.2 Network operating systems
Network Operating Systems (NOS) are usually installed on a powerful server or central host systems on all but the smallest networks. The focus here is on server- (or host-) based network operating systems. Most operating systems, in general, are designed to work with a particular manufacturer's CPUs. Some can run on different manufacturer's CPUs, and some can support multiple CPUs of the same type. Operating systems and CPUs are often classified as to the number of bits they can manipulate in one CPU cycle. The more bits they can manipulate, the more powerful the CPU and OS. Early network operating systems and CPUs were 16-bit. Most of today's network operating systems and CPUs are 32-bit, however some are 64-bit. Examples of network operating systems include UNIX, Windows NT/2000 Server, Novell NetWare, and various mainframe operating systems. Mainframe network operating systems include Digital Equipment VMS, Hewlett Packard MPE, and IBM MVS as well as several varieties of UNIX. Solaris or SunOS is Sun Microsystems' version of UNIX.

Although UNIX is used frequently as a workstation OS for high performance applications, it is not generally considered an end user desktop operating system. It is most often used on servers as a network operating system.