CBSE NOTES CLASS 12 PHYSICS
CHAPTER 15 COMMUNICATION SYSTEMS
It is an interconnection of billions of (users) systems worldwide. It permits communication and sharing of all types of information between any two or more computers connected through a large and complex network. It was started in 1960’s and opened for public use in 1990’s.
Main applications of Internet
- E mail – It permits exchange of text/graphic material using email software. We can write a letter and send it to the recipient through ISP’s (Internet Service Providers) who work like the dispatching and receiving post offices.
- File transfer – FTP (File Transfer Protocol) allows transfer of files/software from one computer to another connected to the Internet.
- World Wide Web (WWW) – Computers that store specific information for sharing with others provide websites either directly or through web service providers. Government departments, companies, NGO’s (Non-Government Organisations) and individuals can post information about their activities for restricted or free use on their websites. This information becomes accessible to the users. Several search engines like Google, Yahoo! etc. help us in finding information by listing the related websites.
- Hypertext is a powerful feature of the web that automatically links relevant information from one page on the web to another using HTML (hypertext markup language).
- E-commerce – Use of the Internet to promote business using electronic means such as using credit cards is called E-commerce. Customers view images and receive all the information about various products or services of companies through their websites. They can do on-line shopping from home/office. Goods are dispatched or services are provided by the company through mail/courier.
- Chat – Real time conversation among people with common interests through typed messages is called chat. Everyone belonging to the chat group gets the message instantaneously and can respond rapidly.