A data communication system is made up of five components.They are:-
1.Message
2.Sender
3.Receiver
4.Medium
5.protocol

A typical data communication system components is shown in the figure below:

1.Message:The message is the information(data)to be communicated.It can consist of text,numbers,pictures,sound or video- or any combination o these.

2.Sender:The senderis the device that sends the data message.It can be a computer,workstation,telephone handset,video camera and so on.

3.Receiver:The receiveris the device that receives the message.It can be a computer,workstation,telephone handset,television and so on.

4.Medium:The transmission mediumis the physical path by which a message travels from sender to receiver.It can sonsist of twisted pair wire,coaxial cable,fiber-optic cable,laser or radio waves(terrestrial or satellite microwave).

5.Protocol:A protocolis a set of rules that govern data communication.It represents an agreement between the communication devices.Without a protocol,two devices may be connected but not communicating,just as a person speaking French cannot be understood by a person who speaks only Japanese.