CHAPTER 1
Internet &
World Wide Web
Topics
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A Brief Introduction to the Internet
The World Wide Web
Web Browsers
Web Servers
Uniform Resource Locator
Tools and Web Programming Languages
Learning Outcomes
At the end of this lesson, students should be
able to:
• Understand history and concepts related
to Internet and World Wide Web.
• Understand a number of tools and web
programming languages that are used in
web development.
A Brief Introduction to the Internet
Origins
• ARPAnet - late 1960s and early 1970s.
• For ARPA-funded research organizations.
• BITnet, CSnet - late 1970s & early 1980s.
• Was built for email and file transfer for
other institutions.
A Brief Introduction to the Internet
• NSFnet - 1986
• Originally for non-DOD funded places.
• Initially connected five supercomputer
centers.
• By 1990, NSFnet had replaced ARPAnet for
non-military uses.
• Soon became the network for all (by 1990).
• NSFnet eventually became known as the
Internet.
A Brief Introduction to the Internet
What the Internet Is
• A world-wide network of computer
networks.
• At the lowest level, since 1982, all
connections use TCP/IP.
• TCP/IP hides the differences among
devices connected to the Internet.
• Internet is actually a network of networks
rather than a network of computers.
A Brief Introduction to the Internet
IP Address
• Every node has a unique numeric address.
• Form: 32-bit binary number.
• Usually written as four 8-bit numbers,
separated by periods.
• Example: 191.57.126.0
8 bits 8 bits 8 bits 8 bits
A Brief Introduction to the Internet
• New standard, IPv6, has 128 bits (1998)
• Organizations are assigned groups of IPs
for their computers.
• Example: A small organization may be
assigned 256 IP addresses, such as
191.57.126.0 to 191.57.126.255.
The World Wide Web
Origins
• Tim Berners-Lee at CERN proposed the
Web in 1989.
• Purpose: to allow scientists to have
access to many databases of scientific
work through their own computers.
The World Wide Web
• Hypertext- text with embedded links to text
in other documents to allow nonsequential browsing of textual material.
• Hypermedia – more than just text –
images, sound, etc.
Web Browser
• Mosaic - NCSA (Univ. of Illinois), in early
1993.
• First to use a GUI, led to explosion of Web
use initially for X-Windows, under UNIX,
but was ported to other platforms by late
1993.
• Browsers are clients - always initiate,
servers react (although sometimes servers
require responses).
Web Browser
• Most requests are for existing documents,
using HyperText Transfer Protocol
(HTTP).
• But some requests are for program
execution, with the output being returned
as a document.
• Example of web browsers: Netscape,
Opera, Internet Explorer, Mozilla, Firefox,
Google Chrome, Safari.
Web Server
• Provide responses to browser requests,
either existing documents or dynamically
built documents.
• Example of web server: Apache, Microsoft
Internet Information Server.
Uniform Resource Locator (URL)
The Structure of URLs
• Taking http://www.mydomain.net/~rdralph/rdralph/ as
an example.
HOW
WHERE
WHO/WHAT
Protocol
Host Domain Name
Directory Path
http://
www.mydomain.net ~rdralph/rdralph/
Uniform Resource Locator (URL)
Common Internet Protocols
• There are several protocols used
commonly on the Internet to get to a
variety of sites which support them.
• The protocol which supports the World
Wide Web - just one component of the
Internet - is http - hypertext transfer
protocol.
Uniform Resource Locator (URL)
Common Internet Protocols
Protocol
file:///
ftp://
http://
mailto:
Type
Example
Local
file:///c|/netscape/bookmark.htm
File
File
ftp://oak.oakland.edu/SimTel/
Transfer
Protocol
Description/Function
•Loads a local file from PC or from a network.
•Opens a file transfer session that allows
user to download and upload (if allowed)
between local PC and the remote computer.
•Anonymous access may be permitted.
•Some FTP sites will require valid accounts.
Hyper
http://www.uncg.edu/~bucknall/tim/ •The protocol for transfer of hypertext
Text
documents written in HTML and JAVA.
Transfer
• The primary protocol for the WWW.
Protocol
Email
mailto:[email protected]
•This protocol calls up the browser's email
screen and posts the completed message to
the email address provided.
•The browser needs to be set up properly to
identify the email server and the identity of
the sender.
Uniform Resource Locator (URL)
Common Internet Protocols
Protocol
Type
Example
Description/Function
news:
Newsgroups news:comp.infosystems
•Provides access to Bitnet, Usenet and
other newsgroup systems.
•User need to know the name of the
newsgroup that they want to access.
•Internet service provider has to allow
access.
•Some newsgroups are not for everyone.
telnet://
Telnet
•Telnet provides a link to a remote
computer.
• In many cases an account to login is
needed.
•In others, user may be allowed to login
as a guest or with a special visitor's ID.
•User needs to know login procedures.
•User also needs to have a telnet
application set up for their browser.
telnet://steffi.uncg.edu/
Uniform Resource Locator (URL)
Host Domain Names
• Form of host domain names:
Service/Machine
Location
Domain
www
uncg
edu
Example: www.uncg.edu
• The Location name is almost always mnemonic an abbreviation of the location name or an
acronym for it.
• A lot of the time the location name is not
abbreviated at all.
Uniform Resource Locator (URL)
• The domain can tell us what type of site we can
expect to be visiting.
Common Domain Acronyms
Domain
Description
.com
Commercial or corporate sites.
.edu
Educational institutions.
.gov
Government sites.
.mil
Military sites.
.org
Sites of associations, organizations, etc.
.net
Network sites.
.fm
Frequency Modulation
Uniform Resource Locator (URL)
• Some sites use a geographical approach
in their domains.
• The last two positions in the domain of a
WWW site outside the US often
represents the country.
• Universal two-letter country codes are
used. For example: my= Malaysia, sa =
Saudi Arabia, uk = The United Kingdom,
sg = Singapore
Uniform Resource Locator (URL)
Paths in URLs
• The tilde (~) generally precedes the name
of a directory assigned to a person.
• In the URL
http://metalab.uniten.edu.my/~mia, for
example, the mia part indicates an
account name associated with the author
mia.
Tools and Web Programming Languages
HTML
• To describe the general form and layout of
documents.
• An HTML document is a mix of content
and controls.
• Controls are tags and their attributes.
Tools and Web Programming Languages
• Tags often delimit content and specify
something about how the content should
be arranged in the document.
• Attributes provide additional information
about the content of a tag.
Tools and Web Programming Languages
XML
• A meta-markup language.
• Used to create a new markup language for
a particular purpose or area.
• Because the tags are designed for a
specific area, they can be meaningful.
• No presentation details.
• A simple and universal way of representing
data of any textual kind.
Tools and Web Programming Languages
JavaScript
• A client-side HTML-embedded scripting
language.
• Only related to Java through syntax.
• Dynamically typed and not object-oriented.
• Provides a way to access elements of
HTML documents and dynamically change
them.
Tools and Web Programming Languages
Java
• General purpose object-oriented
programming language.
• Based on C++, but simpler and safer.
• Focus is on applets and servlets.
Tools and Web Programming Languages
Perl
• Provides server-side computation for HTML
documents, through CGI.
• Perl is good for CGI programming because:
– Direct access to operating systems functions
– Powerful character string pattern-matching
operations
– Access to database systems
Tools and Web Programming Languages
• Perl is highly platform independent, and
has been ported to all common platforms.
• Perl is not just for CGI.
Tools and Web Programming Languages
PHP
• A server-side scripting language.
• An alternative to CGI.
• Similar to JavaScript.
• Great for form processing and database
access through the Web.
Tools and Web Programming Languages
Recent technology in web development:
• AJAX
• Java Web Software (e.g: servlets,
NetBeans, JavaBeans)
• ASP.NET
• Ruby
• Rails
Tools and Web Programming Languages
Tools for Creating Web Page
• Adobe Dreamweaver (Latest version CS5)
• Microsoft Front Page
• Adobe PageMill
References
• Programming the World Wide Web, Sixth Edition
Author: Robert W. Sebesta
Publisher: Addison-Wesley
• NetStrider Tutorial: Uniform Resource Locators
<http://www.netstrider.com/tutorials/URL/>
Last accessed: 22nd June 2009
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