WP SESSION 2 PPT.ppt

Web
Programming
Karnataka LMS 1
Programme B.Sc
Subject COMPUTER SCIENCE
Semester VI
Session No. 2
Topic WWW, Web Browsers, and Web
Servers
Created by Dr Hamela K

Web
• The Web (World Wide Web) consists of information
organized into Web pages containing text and graphic
images.
• It contains hypertext links, or highlighted keywords and
images that lead to related information.
• A collection of linked Web pages that has a common
theme or focus is called a Web site.
• The main page that all of the pages on a particular Web
site are organized around and link back to is called the
site’s home page.
Karnataka LMS 2

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 WWW is the acronym for the World Wide Web.
 It is also commonly known as ‘The Web’.
 The WWW is hypertext based information retrieval tool.
 One can easily surf the Web by jumping from one document to another
using the links in those documents.
 These documents can be in many formats, such as text, graphics,
animation, sound and latest is video.
 They may also be a combination of all these.
 All the information on Internet are presented to the user as a document
or more popularly known as Web Page.
 All these Web Pages are link to each other or even to section within a
Web Page and these links are known as Hyper Links.
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 The tool used to view these Web Pages on Internet is known as Internet
browser or simply browser
 It is a software program specifically developed to extract information on user
request from the Internet and present them as a Web Page to the viewer.
 There are several browsers available in the market.
 The most popular are Internet Explorer from Microsoft and Netscape from
Netscape Inc.
 The process of using browser to view information on Internet is known as
Browsing
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Client/Server Structure of the Web
 Web is a collection of files that reside on computers, called
Web servers, that are located all over the world and are
connected to each other through the Internet.
 When we use our Internet connection to become part of the
Web, our computer becomes a Web client in a worldwide
client/server network.
 A Web browser is the software that you run on your computer
to make it work as a web client.
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WEB BROWSER
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*Source:https://networkencyclopedia.com/web-browser/
Fig 1: Web Browser*

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 A software application used to access information on the World Wide Web is
called a Web Browser. When a user requests some information, the web browser
fetches the data from a web server and then displays the webpage on the user’s
screen.
 The main function is to retrieve information from the World Wide Web and
making it available for users
 Visiting any website can be done using a web browser. When a URL is entered in
a browser, the web server takes us to that website
 To run Java applets and flash content, plugins are available on the web browser
 It makes Internet surfing easy as once we reach a website we can easily check the
hyperlinks and get more and more useful data online
 Multiple webpages can be opened at the same time on a web browser
 Options like back, forward, reload, stop reload, home, etc. are available on these
web browsers, which make using them easy and convenient
WEB BROWSER

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 Google Chrome
 Microsoft Edge
 Mozilla Firefox
 Apple’s Safari
 Sogou Explorer
 UC Browser
 Opera
Popular Web Browsers

Architecture of a Browser
The browser’s main functionality is to fetch the files from the
server and to display them on the screen.
It basically displays html files containing images, PDF, videos,
flashes, etc in an ordered layout.
A browser is a group of structured codes that performs plenty
of tasks to display a webpage on the screen.
These codes are separated in to different components
according to their tasks performed.
The Architecture of a browser is shown in the below image.
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Fig 2: Web Browser Architecture*
*Source: https://medium.com/@monica1109/how-does-web-browsers-work

1. User Interface – It is the space where interaction between users and the browser occurs.
Most of the browsers have common inputs for user interface. Some of them are - an address bar,
next and back buttons, buttons for home, refresh and stop, options to bookmark web pages, etc.
2. Browser Engine – It is the piece of code that communicates the inputs of user interface
with the rendering engine. It is responsible for querying and manipulating the rendering engine
according to the inputs from various user interfaces.
3. Rendering Engine – It is the part thoroughly responsible for displaying the requested
content on the screen. It first parses the html tags and then using the styles, it builds a render
tree and finally a render layout, which displays the content on the screen.
4. Networking – The fraction of the code written in the browser, responsible to send various
network calls. For example sending the http requests to the server.
5. Java Script Interpreter – It is the component of the browser written to interpret the java
script code presented in a web page.
6. UI Backend – This draws basic widgets on the browser like combo boxes, windows, etc.
7. Data Storage – It is small database created on the local drive of the computer where the
browser is installed. This database stores various files like cache, cookies, etc.
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WEB SERVERS
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 A Web server is a program that generates and transmits
responses to client requests for Web resources.
 Handling a client request consists of several key steps:
 Parsing the request message
 Checking that the request is authorized
 Associating the URL in the request with a file name
 Constructing the response message
 Transmitting the response message to the requesting client

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 The server can generate the
response message in a variety of
ways:
 The server simply retrieves the
file associated with the URL and
returns the contents to the
client.
 The server may invoke a script
that communicates with other
servers or a back-end database
to construct the response
message.
Fig : Web Server Architecture*
*Source:https://docs.oracle.com/cd/B10501_01/network.920/a96580/intro.htm

IIS WEB SERVER APACHE TOMCAT SERVER
IIS Webserver is operating system
dependent. It runs in only windows
environment
Apache webserver is operating system
independent. (i.e.) Apache can run on
almost any OS including UIX, Apple OS, and
on Linus OS
IIS is developed by Microsoft Apache is developed by Apache Foundation
IIS server runs in user space and kernel
space
Apache server runs in user space
IIS is not Open Source Apache Webserver is open source
IIS is both webserver and application server Apache tomcat server is only webserver
IIS has a dedicated staff to answer most
problems
Support for Apache comes from the
community itself
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Session Overview
• WWW
• Web Browser
• Web Server

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References
Robert W Sebesta, “Programming the World Wide Web”, 4th Edition, Pearson
Education, 2008.
M.Deitel, P.J.Deitel, A.B.Goldberg, “Internet & World Wide Web How to program”, 3rd
Edition, Pearson Education / PHI, 2004.
Chris Bates, “Web Programming Building Internet Applications”, 3rd Edition, Wiley
India, 2006.
Web Programming, Chitra Ravi, Subhas Stores, Bangalore
Web Programming in Simple steps, Srikanth S, Skyward Publishers, Bangalore
Web Programming, Dr. K Murugan, Sunstar Publication, Bangalore
https://byjus.com/govt-exams/web-browser/

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