• Communication is the transfer of information from one person to another, whether  or not it elicits confidence. But the information transferred must be understandable to the receiver – G.G. Brown.
  • The exchanging of information by speaking, writing, or using some other medium.- Oxford Dictionary
Components of a Communication System

There are following major components a communication system has –

  • Sender/Source/Transmitter : A source who/which is trying to send a message to the receiver. It produces a message.
  • Message/Data/Signal : The actual content in communication for receiver.
  • Medium/Channel : The medium (mostly air/wire) through which data is transmitted in the form of signal.
  • Devices : Several related/networking devices are also used to transmit the data with certain specific modifications as per need. For example – Modem, Encoder, Decoder etc
  • Receiver/Destination : A destination who/which is trying to receive a message.
Data Transmission Types
(A) Serial Data Transmission

(a) Synchronous Data Transmission

(b) Asynchronous Data Transmission

(B) Parallel Parallel Transmission
Data Transmission/Communication Modes
(A) Simplex Transmission
    • Simplex transmission is one-way transmission.
    • It is also called unidirectional because the signal travels in only direction.
    • For example – Radio & TV Set. 
(B) Half Duplex Transmission
    • When data transmission can take place in both directions, but not at the same time rather one at a time  i.e.  only one side either sender or receiver can transmit at a time.
    • For example – walky-talky & citizen’s band.
(C) Full Duplex/Duplex Transmission
    • The transmission of data between sender and receiver can take place in both directions at the same time.
    • For example – telephone or mobile conversation is an example of full-duplex
      communication, where both sender and receiver can hear and say something to each other at the same time.


  • network is a collection of more than one computers, servers, mainframes, network  devices, peripherals, or other related devices connected to one another in pre-defined plan to allow the sharing of data/resources.
  • network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information.
  • An excellent example of a computer network is the Internet.


  • Increases productivity.
  • Store vast amounts of information and reduce waste.
  • Keeps us connected to all the nodes of a network.
  • Improves system abilities.
  • Save time & cost.


  • Viruses can spread to other computers throughout a computer network.
  • Purchasing the network cabling, equipment and file servers can be expensive.
  • Comparatively complex structure than standalone system. 
  • It lacks independence.
  • It poses security difficulties.
  • It lacks robustness.
  • It requires an efficient/skillful handler.
  • It requires an expensive set-up.

Applications/Uses of Computer Network

There are following general applications of a computer network in an environment: –

  • Resource sharing
    • It allows sharing of all programs, equipment and data available to anyone component on the network irrespective of the physical location of the resource and the user.
    • Using computer networks, we can share any resource, CPU processing power, peripherals (like printers, scanners, etc) information (like files and data and even software) etc among the components of that network. This sharing is done by communicating the machine through whom we want to share.
    • In hardware sharing, users can share devices present in that network such as printers, scanners, CD/DVD-ROM drives, hard drives etc.
  • Reliability/Flexibility
    • It provides high reliability in its service having alternative sources of data if one of them is unavailable due to hardware failure or any other reason, the other source is available and can be used.
  • Powerful communication
    • Using computer networks, users can share their personal communication/message through the computer networks as email, chatting, audio/video conferencing, etc.
    • It provides a powerful communication medium among widely separated users.
  • Inexpensive
    • Data transmission through a computer network is believed to be comparatively inexpensive.
  • Information Broadcasting and Search
    • This is also a mostly used applications these days to create a new website, blogs, social networking website, search engines, etc.
    • Computer network provide us tremendous opportunity for information broadcasting, display, searching and information retrieval. 
  • Storage capacity
    • A computer network provides a huge capacity to store data reliably.
  • Cost Efficient
    • The output of computer network is believed to be very cost efficient with respect to single/standalone system.
  • Some Specific Applications
    • To make Computer network environment for a Campus for computing and                     resources sharing work mainly.
    • In Collaborative research and development work.
    • In developing, Integrated system for design + manufacturing + inventory.
    • In making, Electronic commerce, publishing and digital libraries.
    • In Multimedia communication (tele-training, video conferencing etc.)
    • In Health-care delivery (remote diagnosis, telemedicine etc.)system.
    • To use Video-on-demand facility.
    • In On-line learning.

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