Like DOS, a network operating system works behind the scenes to provide services for users and application programs. But instead of controlling the pieces of a single computer, a network operating system controls the operation of the network system, including who uses it, when they can use it, what they have access to, and which network resources are available. At a basic level, the NOS allows network users to share files and peripherals such as disks and printers.
Most NOSs do much more.
They provide data integrity and security by keeping people out of certain resources and files. They have administrative tools to add, change, and remove users, computers, and peripherals from the network. They have troubleshooting tools to tell network managers what is happening on the network. They have internetworking support to tie multiple networks together. At the heart of the NOS is redirection.