A LAN Operating System, or Network Operating System (NOS), is software that provides the network with multi-user, multitasking capabilities. The operating system facilitates communications and resource sharing, thereby providing the basic framework for the operation of the LAN. The operating system consists of modules that are distributed throughout the LAN environment. Some NOS modules reside in servers, while other modules reside in the clients.
A client is an application that generally resides on a microcomputer. The application can be word processing, a spreadsheet, or a database. The client runs against a server, a multiport computer that contains large amounts of memory, allowing multiple clients to share the servers resources, while performing certain functions independently.
In addition to supporting multitasking and multi-user access, LAN operating systems provide for recognition of users based on passwords, user IDs, and terminal IDs. On the basis of such information, LAN operating systems can manage security using access privileges. Additionally, a LAN operating system provides multiprotocol routing, as well as directory and message services. DOS-based LAN operating systems include Novell NetWare and Sun Microsystems’ TOPS/DOS. OS/2 and UNIX-based LAN operating systems include Banyan VINES, IBM LAN Server, Microsoft LAN Manager, and Novell SIT NetWare.