A network operating system (NOS) is a software program that controls other software and hardware that runs on a network. It also allows multiple computers, also known as network computers, to communicate with one main computer and each other, so as to share resources, run applications, and send messages, among other things. A computer network can consist of a wireless network, local area network (LAN), a wide area network (WAN), or even two or three computer networks. The heart of any of these networks, however, is the network operating system.
There are different types of operating systems. Most individual computer users run client operating systems, like Windows XP®, which run on a single computer. Personal computers that individuals use at home have a client operating system which manages the interactions and processes between the computer and its peripherals such as the keyboard, mouse, external monitor, and printer. In a sense, this is also a network, though it is different in scale than a network operating system which manages the interactions of many computers.
A network usually consists of many network computers that are connected to a central hub or router. The central hub, in turn, is connected to a larger, main computer. The network may also include other devices like printers, a tape-backup system, and a central storage facility. The main network computer runs all the connected computers and devices with the help of the operating system software.