A Communication is the process of transferring messages from one point to another. It is a very vital process in a network. When two networks are connected with each others they have to share data to each others so this process of communication system has three basic elements which are as follows - 1. A sender (source), which creates the message to be transmitted. 2. A medium, which carries the message, 3. A receiver (sink), which receives the message. Data communication is the function of transmitting data from one point to another. In this case, the sender and receiver are normally machines, in particular, computer devices (computers, terminals, peripheral devices like printers, plotters, disks, etc), and the transmission medium may be telephone lines, microwave links, satellite links, etc. However, the messages that are transmitted are only in data form, but not in voice conversations form. Hence, the electronic systems, which transfer data from one point to another, are called dat