On a client/server network, every computer has a distinct role, that of either a client or a server. A server is designed to share its resources among the client computers on the network. Typically, servers are located in secured areas, such as locked closets or data centers, because they hold an organization’s most valuable data and do not have to be accessed by operators on a continuous basis. The rest of the computers on the network function as clients.

Server: A dedicated server computer typically has a faster processor, more memory, and more storage space than a client because it might have to service dozens or even hundreds of users at the same time. High-performance servers also might use two or more processors, use the 64-bit version of the PCI expansion slot for server-optimized network interface cards, and have redundant power supplies. The server runs a special network operating system—such as Windows NT Server, Windows 2000 Server, Windows Server 2003, Linux, Unix, or Novell NetWare—that is designed solely to facilitate the sharing of its resources. These resources can reside on a single server or on a group of servers. When more than one server is used, each server can “ specialize” in a particular task (file server, print server, fax server, email server, and so on) or provide redundancy (duplicate servers) in case of server failure. For very demanding computing tasks, several servers can act as a single unit through the use of parallel processing.

Client: A client computer communicates only with servers, not with other clients. A client system is a standard PC that is running an operating system such as Windows 9x, Windows Me, Windows2000 Professional, or Windows XP. These versions of Windows contain the client software that enables the client computers to access the resources that servers share. Older operating systems, such as Windows 3.x and DOS, require add-on network client software.