A computer network connects two or more autonomous computers. Networks supply their users with communication channels. Exchange of messages is controlled by communication protocols. Networking is needed to share computer files, to share computer peripheral, to enable different computers to communicate with each other. The three main components of network are the sender, communication channel and the receiver.
When computers are connected via telephones, a modem is also used to convert the computer generated signal (digital signal) into a form that can be carried by telephone cables (analog signal). When the cables connect two or more workstations it is known as transmission media or communication channels of network. The communication media is divided in two categories: guided media and unguided media. The three basic types of Guided Media are Twisted Pair, Coaxial Cable and Optical Fibre. Twisted pair cable consists of two identical wires wrapped together in a double helix. Coaxial Cable is a hollow outer cylindrical conductor surrounding a single view. It is used for TV, long distance telephone and LANs. Optical fibres consist of thin strands of glass like material, which are so constructed that they carry light from a source at one end of the fibre to a detector at the other end.
Unguided media can be categorized as Long distance media and Short distance media. Long distance wireless communication media includes: radio wave, microwave and satellite. Short distance wireless media includes infrared, laser, Bluetooth, Wi-Fi and WiMax. Modem is a device attached to computers that can convert digital signals to analog signal and vice-versa. A computer network is a collection of computing devices connected in order to communicate and share resources. There are three types of networks local area network, metropolitan area network and wide area network.