A computer network is a system of interconnected computers. The computers of a network communicate with one another and share applications, data, voice and videos, and hardware components. There are three main types of computer networks, they are:

LAN: It provides high speed communication between computers situated in a limited area, normally within a building or a small area like a college/university campus. LANs are typically owned and managed by a single organization.

WAN: This network spreads over a large geographical region and may attach computers within a country or cover many countries. WANs may be provided by telegraph and telephone organizations, they may be private to a single association or they may be controlled by a group of organizations. Usually, WANs have been implemented using packet switching and circuit switching technologies. A WAN can link a number of LANs. The internet is a popular example of WAN.

MAN: These networks cover an area of a typical city or town. They offer a trouble-free and fast way to connection different sites of a society for exchange of information. Mans use technologies similar to LAN technologies.

Uses of Computer Networks:Computer networks provide many benefits. Major uses of computer networks are:

• Simultaneous access to programs and data.
• Sharing peripheral devices like printers, scanners etc.
• Personal communications using e-mail
• Aiding communication by teleconferencing and video-conferencing.
• Protecting information by account name and password.

Some Network Terminologies: Network Topology: Topology of a network describes the way the computers and the nodes of the network are interconnected. There are a number of possible topologies:

• Bus topology
• Star topology
• Tree topology
• Ring topology
• Mesh topology.

Links: The physical connections that connect the nodes are known as links. A link may be through a pair of wires, a coaxial cable, and an optical fiber or through a satellite. The data transmission rates of the links are expressed by kbps (kilo bits per second), Mbps (Mega bits per second), Gbps (Giga bits per second) or Tbps (Tera bits per second). Examples are 64 kbps, 2 Mbps and 2.4 Gbps etc.

Media: The most commonly used media for computer networks are twisted pair, co-axial cable and optical fibre. Wireless techniques include broad-cast radio waves, microwaves and infrared.

Network Protocols: Computers of a network must obey some rules when communicating with each other. This set of rules forms the protocol for a computer network. The structural set of modules that implements the communication functions is called protocol architecture. An example of common protocol architecture is the TCP/IP protocol suite.