[edit] History

This section requires expansion.

Early networks of communicating computers included the military radar system Semi-Automatic Ground Environment (SAGE), started in the late 1950s, and its relative the commercial airline reservation system Semi-Autom atic Business Research Environment (SABRE) which went online with two connected mainframes in 1960.[1][2]  Later in the 1960s, the Advanced Research Projects Agency (ARPA) started funding the design of the Advanced Research Projects Agency Network (ARPANET) for the United States Department of Defense. Development of the network began in 1969.[3] The ARPANET evolved into the modern Internet.

[edit] Purpose

Computer networks can be used for a variety of purposes:

Facilitating communications Using a network, people can communicate efficiently and easily via email, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.Sharing hardware In a networked environment, each computer on a network may access and use hardware resources on the network, such as printing a document on a shared network printer.

; Sharing files, data, and information : In a network environment, authorized user may access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks. ; Sharing software : Users connected to a network may run application programs on remote computers. ==Network classification== The following list presents categories used for classifying networks.

[edit] Connection method

Computer networks can be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as optical fiber, Ethernet, wireless LAN, HomePNA, power line communication or G.hn.