A computer network is a telecommunications network that allows computers to exchange data. The physical connection between networked computing devices is established using either cable media or wireless media. The best-known computer network is the Internet.
Network devices that originate, route and terminate the data are called network nodes.[1] Nodes can include hosts such as servers and personal computers, as well as networking hardware. Two devices are said to be networked when a process in one device is able to exchange information with a process in another device.
Computer networks support applications such as access to the World Wide Web, shared use of application and storage servers, printers, and fax machines, and use of email and instant messaging applications. The remainder of this article discusses local area network technologies and classifies them according to the following characteristics: the physical media used to transmit signals, the communications protocols used to organize network traffic, along with the network's size, its topology and its organizational intent.
History
Before the advent of computer networks, communication between calculation machines and early computers was performed by human users by carrying instructions between them. Today, in spite of the wide use of email and other networking applications, people do continue to transfer information to another person's computer by hand-carrying removable storage media (such as flash drives) — a method jokingly known as "sneakernet". * In September 1940, George Stibitz used a teletype to send instructions for a problem set from his Model at Dartmouth College to his Complex Number Calculator in New York and received results back by the same means. * In the late 1950s, early networks of communicating computers included the military radar system Semi-Automatic Ground Environment (SAGE). * In 1960, the commercial airline reservation system semi-automatic