Choosing NOS can be a complex and a difficult decision. Every popular NOS has its strengths and weaknesses. NOS may cost thousands of dollars depending on the number of clients that will connect to the server. Many networks now include more than one server type, and knowing how to get these diverse systems to interoperate is an important skill for a network administrator. Operating systems on the network have their own language. Different NOS vendors use the same terms in different ways. For example, in a UNIX environment, “root” refers to the master administrative account, but in NetWare networks, it is used to identify a Novell directory services (NDS) object. In Windows, root can relate to the domain at the top of a Windows 2000 or XP domain tree or to the basic component of a Distributed File System (DFS).  Linux  Windows NT  NetWare

Linux is an operating system for computers, comparable to Windows or Mac OS X. It was originally created by Linus Torvalds. Linux resembles UNIX, but unlike UNIX, Linux is both Free Software and open source software. Linux runs on a wide variety of hardware platforms, from huge mainframes to desktop PCs to cell phones. Linux haves two parts, a kernel, which is the basic interface between the hardware and other system software, and the functions that run on top of it, such as a graphical user interface (GUI) and application programs. No company sells Linux because it is an open sourced which is released to everyone.

Windows NT is a Microsoft Windows personal computer operating system designed for users and businesses needing advanced capability. Windows NT has two parts, Microsoft NT Workstation and Microsoft NT Server. The Workstation is designed for users, especially business users, who need faster performance and a system a little more fail-safe. The Server is designed for business machines that need to provide services for network-attached computers. The Server is required, together with an Internet server such as Microsoft's Internet Information Server (IIS), for a Windows system that plans to serve Web pages. The NT Server is probably the second most installed network server operating system after Novell's NetWare operating system. Microsoft claims that its NT servers are beginning to replace both NetWare and the various Unix-based systems such as those of Sun Microsystems and Hewlett-Packard. NT Server 5.0. Essentially became what was renamed Windows 2000.

NetWare is a software product that runs on a variety of different types of LANs, from Ethernets to IBM token-rin networks. It provides users and programmers with a consistent interface that is independent of the actual hardware used to transmit messages. An early - and primary competitor was the Microsoft Window NT operating system.