WWW (World Wide Web)

History of World Wide Web:
 In 1989-1990, Tim Berners-Lee invents the World
Wide Web at CERN.
 It is published in 1992.
 It is used for transferring text and graphics
simultaneously.
 It is simple and easy to use.

What is World Wide Web?
 The World Wide Web is a way of exchanging
information between computers on the Internet.
 The World Wide Web can be viewed as a huge
distributed system consisting of millions of clients
and servers for accessing linked documents.


The WWW is essentially a huge client-server system
with millions of servers distributed world wide.
 Each server maintains a collection of documents.
 Each document is stored as a file.
 A server accepts requests for fetching a document and
transfers it to the client.

Uniform Resource Locator:
The simplest way to refer the document is by means of
a reference called a “Uniform Resource Locator (URL)”.
 It is defined as the global address of document and
other resource on the WWW.
 A URL is one type of Uniform Resource Identifier
(URI) i.e; the generic term for all types of names and
addresses.

Document Model:
 The Web is that all information is represented by
means of documents.
 Some documents are as simple as an ASCII text file,
while others are expressed by a collection of scripts that
are automatically executed when the document is
downloaded into a browser.
 Most Web documents are expressed by means of a
special language called HTML.

Simple HTML Program:
<html>
<body>
<H1> Hello World </H1>
<script type=“text/java script”>
document.writeln (“<H1>Hello World</H1>”);
</script>
</body>
</html>

Document Types:
 There are many other types of documents besides
HTML and XML.
 For example, a script can also be considered as a
document.
 The other examples include documents formatted in
postscript or PDE, images in JPEG or GIF or audio
documents in mp3 format.

Communication:
All communications in the Web between clients and
servers is based on the HTTP.
HTTP is a relatively simple client-server protocol.
 A client sends a request message to a server and waits
for a response message.
 An important property of HTTP is that it is stateless.

Advantages:
Availability of mainly free information.
 It helps us for fast browsing .
 It provides security.
 lt is accessible from anywhere, so it became the global
media.

WWW (World Wide Web)

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