Chapter 9 Computer Network IP 12 | Important Notes Computer Network

What is Internet?

“Interconnected Network”

Internet is independent global network system of countless computers and electronic devices scattered around the globe connected to each other wirelessly or wirely with the help of various devices such as satellite, routers, wires and modems, for sharing information and communicating with each other.

Evolution of Internet

Application of Internet

• WWW
• Email
• Chat
• VoIP

World Wide Web

World Wide Web popularly called ‘Web’ is a leading information sharing service of the Internet, which was developed by Tim Berners Lee in 1989 to give user access to wide range of documents that are connected to each other by hyperlink and written in HTML.

• Content of HTML documents can be any text, graphics, audio or video.
• Every HTML Document is can be accessed by its unique address known as URL
• To read HTML Documents Web Browser is used.
• HTTP is used to transfer documents from Server to Client.

Difference between Internet and WWW

Internet	WWW
Internet is primarily hardware based	WWW is primarily software based
Internet is networking infrastructure that connects devices together	WWW is collection of information that can be access through Internet
Internet uses TCP/IP for communication	WWW uses HTTP/HTTPS for communication

Website

A website is collection of web pages which can be interlinked with each other, hosted on a web server and written using HTML.

Content of a Website

• Web Page
• Home Page
• Hyperlink
• Hypertext
• Web Address (URL)
• Content
• Design

Web Page

• A Web page is a document written in HTML and available on the WWW that can be viewed in Browser by anyone connected to Internet.
• Content of a Web page can be of any type such as text, graphics, audio or video etc.
• Web pages can be linked with each other using hyperlink.

Home Page

• A Home Page is basically a Web Page of a website that appears first of all when a user opens that website.
• A Home page allows us to navigate to other page via menu system or links.
• A Home page sets the appearance of the website.

Types of Web Pages

• Static Web Page: The Web page which content is fixed and remain same for all the user every time it is viewed.
• Dynamic Web Page: The Web page which content is not fixed and display different content to different user every time is opened.

Difference between Static and Dynamic web page

Static Web Page	Dynamic Web Page
Content of it is fixed every time it is viewed	Display different content every time it is viewed
It is written using HTML Code.	It is written using HTML and scripting language like PHP, Java etc.
It is updated rarely	It is updated frequently
It takes less time for uploading	It takes more time compared to static web page for uploading

URL

A URL stands for Uniform Resource Locator also referred to as web address is a unique identifier used to specify unique address of a website. For example https://www.microsoft.com

Compoents of URL:

• Protocol
• Name or Address of Server
• Location of File on Server

Absolute and Relative URL

Absolute URL contains complete address from HTTP(Protocol) to domain name and directory/page path that gives the complete information about the file location path.

For example : https://www.techtipnow.in/download.php

Relative URL does not use complete address but contains the file path excluding the domain name. It tells the URL location in terms of the current location. It assumes that the link you add is on the same site and is part of root domain.

For exp: download/index.html

Web Server

Web Server: A web server is a computer used to store and respond to web related request. It handles HTTP request and deliver web pages.

• Web Server is used for Web hosting or hosting for website or web application.
• Web Server can also support FTP and SMTP.
• A Web Server may consist of Hardware and Software both.
• Web Server hardware is basically a computer which stores Web Server software and content related to website such as text, images, html and css code, script code, audio/video files etc.
• Web Server software are programs that accept http request from web browser and respond those request.

Web Hosting

Web hosting is a service that provide resources such as CPU, RAM, Storage, connection and necessary services to store, manage and serve a website or application in Internet and make it part of www. Once a website or application is hosted, it can be accessed from any computer connected to Internet.

Web Browser

A Web browser is an application software which enable use to view information available in Internet. It display information retrieved from web server in HTML format.

Examples-

• Google Chrome
• Mozilla Firefox
• Internet Explorer
• Opera

Email

Email stands for Electronic mail. It is an application of Internet used to send written messages to individual or many located at different places.

Email Address

The structure of an email address consists of two parts:

• Username
• Domain name

‘@’ is used to separate these two parts.

Email Components (Structure of Email)

The structure of an email message contain following components:

• To: specifies the email address of the recipients
• Cc: stands for Carbon Copy. It specifies the email addresses of people to whom we are sending copy of email.
• Bcc: stands for Blind Carbon Copy. It also specifies the email addresses of people to whom we are sending copy of email. However email address appearing in the bcc field will not appear in the email header.
• Subject: specifies the subject of email.
• Message Body: specify actual message being sent.
• Attachment: allows you to attach files and images in the email.

Difference between cc and bcc

CC	BCC
Email addresses in cc are visible to all the recipients	Email address in bcc field are not displayed to any of the recipients.
If Reply To All is selected, All recipients receive reply	If Reply To All is selected, recipients do not receive reply.

VoIP

Voice Over Internet Protocol is a technology that makes audio and video calls possible from any internet-connected device having a microphone and speakers.

It is useful because of its-

• Lower cost
• Increased functionality

Advantages/Disadvantages of VoIP

Advantages:

• It is cost effective.
• It is easily available.

Disadvantages:

• There is no guarantee of audio/video quality.
• It may not work for emergency service numbers like police or fire services.
• It depends upon Internet Protocol.

Chat

Chat is a real time communication service on the Internet that offers an instant transfer of messages between people at different geographic location.

For chatting all who are communicating must be online at the same time and using same application.

Some popular chat software are-

• Google Talk
• Skype
• Yahoo Messenger
• WhatsApp
• Google Hangout
• rediff Messenger etc.

Cookies

Cookies are small text files stored on a user’s computer and created and used by websites to remember basic information or to record the user’s browsing activity.