09-03-2012, 04:29 PM
Data Communication and Networking
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Introduction
Today computer is available in many offices and homes and therefore there is a
need to share data and programs among various computers. With the advancement
of data communication facilities the communication between computers has
increased and thus it has extended the power of computer beyond the computer
room. Now a user sitting at one place can communicate with computers of any
remote site through communication channel. The aim of this lesson is to
introduce you the various aspects of computer network.
Data Communication
We all are acquainted with some sorts of communication in our day to day life.
For communication of information and messages we use telephone and postal
communication systems. Similarly data and information from one computer
system can be transmitted to other systems across geographical areas. Thus data
transmission is the movement of information using some standard methods.
These methods include electrical signals carried along a conductor, optical
signals along an optical fibers and electromagnetic areas
Basic Elements of a Communication System
The following are the basic requirements for working of a communication
system.
1. The sender (source) who creates the message to be transmitted
2. A medium that carries the message
3. The receiver (sink) who receives the message
Communication Protocols
You may be wondering how computers send and receive data across
communication links. The answer is data communication software. It is this
software that enables us to communicate with other systems. The data
communication software instructs computer systems and devices as to how
exactly data is to be transferred from one place to another. The procedure of
data transformation in the form of software is commonly known as protocol.
The data transmission software or protocols perform the following functions
for the efficient and error free transmission of data.
Digital and Analog Transmission
Data is transmitted from one point to another point by means of electrical signals
that may be in digital and analog form. So one should know the fundamental
difference between analog and digital signals. In analog signal the transmission
power varies over a continuous range with respect to sound, light and radio waves.
On the other hand, a digital signal may assume only discrete set of values within
a given range. (see fig. 5.2 and 5.3) Examples are computer and computer related
equipment. Analog signal is measured in Volts and its frequency is in Hertz (Hz).
