A communication service enables the exchange of information between users at different locations.
Communication services & applications are everywhere. Some examples are given below
Need for Computer Communication over Distances
Computer communication has become essential for the following reasons:
(a) Computers can send data at a very fast speed over long distances using satellite and microwave links. Therefore, the cost of transfer of documents using computers is cheaper than
other conventional means like telegrams.
(b) Computers can have fax system integrated with them. This allows them to send pictures along with the text. Thus the newspaper reports can be prepared and sent all over the world at a very high speed by composing and publishing them from different centers.
(c) The time taken to transmit the messages is very small. Hence different computers can be
connected together and the users can work together as a group. Software packages have
been developed for group working in Data Base Management (DBMS) and graphic works.
(d) Different departments of an organization may be separated physically being at distant places
but their data could be stored on a central computer. This data is accessed by computers
located in different departments. The data at the central computer may be updated from time to time and accessed by all users. This prevents any bottlenecks in the smooth functioning of the organization. The latest data (say for inventory) will be easily available at all times to all the users.
(e) Fluctuations of prices in foreign exchange and shares/equities can be communicated instantaneously
using the medium of computer communications only. The transfer can be accelerated and verified at any instant of time.
Data Communication is defined as the exchange of data between two devices via some form of transmission medium such as a wire cable. The communicating devices must be a part of a communication system made up of a combination of hardware ( physical equipment) and software (programs).
Characteristics of data Communication :
The effectiveness of a data communication depends on three characteristics
Delivery : The system must deliver data to correct destination.
Accuracy: The system must deliver data accurately.
Timeliness: The system must deliver data in a timely manner. Data delivered late are useless. Timely delivery means delivering data as they are produced, in the same order that they are produced. and without significant delay. This kind of delivery is called real –time transmission.
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