A computer network links several computers. Together, they can do much more than a single computer. Office networks allow people to work as a team. At home, a network allows two or more computers to share a printer. Local-area networks (LANs) like these can be linked into wide-area networks (WANs) that may cover a country or span the globe.
Networks often contain devices that make them work better. In large networks, the flow of information can be controlled by routers and bridges. Routers send data to where it is needed. Bridges link two smaller networks and can prevent parts of one network seeing data from parts of the other. The simplest device, a hub, connects several computers to a shared resource, such as a printer.
A local-area network is usually connected with cables similar to those used for telephones. The most popular network system is Ethernet, which allows communication at up to 12 megabytes per second. An Ethernet network can be a straight line network (also called a “bus” network), or a star network. One computer, called the network server, controls communications within the network.
In a star network, each computer is connected to the server by its own cable. It is more reliable than a line network because a broken wire affects only one or two computers.