WWW: The World Wide Web (WWW) is a repository of information linked together from points all over the world. The WWW has a unique combination of flexibility , portability, and user-friendly features that distinguish it from other services provided by the Internet.

1. World Wide Web
By Dr R Jegadeesan
Jyothishmathi Institute of technology and
Science karimnagar

2. • The World Wide Web (WWW) is a repository of
information linked together from points all over the
world.
• The WWW has a unique combination of flexibility ,
portability, and user-friendly features that
distinguish it from other services provided by the
Internet.
• The WWW project was initiated by CERN (Conseil
Européen pour la Recherche Nucléaire) European
Organization for Nuclear Research.

3. ARCHITECTURE

4. • Each site holds one or more documents,
referred to as Web pages.
• Each Web page can contain a link to other
pages in the same site or at other sites.
• The pages can be retrieved and viewed by
using browsers.

5. • In the above figure the client needs to see some
information that it belongs to site A.
• It sends a request through its browser, a
program that is designed to fetch Web
documents.
• The request, among other information,
includes the address of the site and the Web
page, called the URL

6. • The server at site A finds the document and
sends it to the client.
• When the user views the document, she/he
finds some references to other documents,
including a Web page at site B.
• The reference has the URL for the new site.
• The user is also interested in seeing this
document.
• The client sends another request to the new
site and the new page is retrieved.

7. Client (Browser)
• A variety of vendors offer commercial browsers
• Each browser usually consists of three parts:
Controller
 Client Protocol
 Interpreters.

8. Client (Browser)

9. • The controller receives input from the keyboard or
the mouse and uses the client programs to access
the document.
• The client protocol can be one of the protocols
such as FTP , HTTP, SMTP, TELNET
• After the document has been accessed, the
controller uses one of the interpreters to display
the document on the screen.
• The interpreter can be HTML, Java, or
JavaScript, depending on the type of document.

10. Server
• The Web page is stored at the server.
• Each time a client request arrives, the
corresponding document is sent to the client.
• To improve efficiency, servers normally store
requested files in a cache in memory;
memory is faster to access than disk.
• A server can also become more efficient
through multiprocessing.
• In this case, a server can answer more than
one request at a time.

11. • A client that wants to access a Web page
needs the address.
• URL is the global address of documents on
the World Wide Web.
• The URL defines four things:
Protocol
Host Computer
 Port
 Path

12. Uniform Resource Locator

13. Protocol
• The protocol is the client/server program
used to retrieve the document.
• Many different protocols can retrieve a
document; among them are FTP or HTTP.
• The most common today is HTTP.

14. Host
• The hostname is basically the “domain” to
which the URL is referring.
• The hostname can actually be broken down into
several parts:
• .com .edu .net— this is actually the “top level
domain.”
• “example.com” is often referred to as the “sub
domain” for the .com top level domain..
• Host names are usually begin with the
characters "www".

15. Port
• The URL can optionally contain the port
number of the server.
• If the port is included, it is inserted between the
host and the path, and it is separated from the
host by a colon(:)
• URL : http://www.example.com:8080/path/

16. Path
• Path is the pathname of the file where the
information is located. Note that the path can
itself contain slashes
• For example
• https://en.wikipedia.org/wiki/Main_Page#/me
dia/File:Irises-Vincent_van_Gogh.jpg

17. WEB DOCUMENTS
• The documents in the WWW can be grouped
into three broad categories:
Static documents
 Dynamic documents

18. Static documents
• Static documents are fixed-content documents that are created
and stored in a server.
• The client can get only a copy of the document.
• In other words, the contents of the file are determined when
the file is created, not when it is used.
• Of course, the contents in the server can be changed, but the
user cannot change them.
• When a client accesses the document, a copy of the document
is sent.
• The user can then use a browsing program to display the
document

19. • Hypertext Mark-up Language (HTML) is a
language used to create static Web pages

20. Dynamic documents
• A dynamic document is created by a Web
server whenever a browser requests the
document.
• When a request arrives, the Web server runs
an application program or a script that
creates the dynamic document.
• A very simple example of a dynamic
document is the retrieval of the time and date
from a server.

22. • The Common Gateway Interface (CGI) is a
standard for creating and handling dynamic
Web documents.
• A CGI program with its embedded CGI
interface tags can be written in a language
such as C, C++, Shell Script, or Perl.