CHAPTER 1 Internet & World Wide Web. Topics A Brief Introduction to the Internet The World Wide Web Web Browsers Web Servers Uniform Resource Locator

CHAPTER 1Internet &

World Wide Web

Topics

• 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.


• 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.


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.


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: 191.57.126.08 bits8 bits 8 bits 8 bits


• 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 non-sequential 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/


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.


Protocol Type Example Description/Function

file:/// Local File

file:///c|/netscape/bookmark.htm •Loads a local file from PC or from a network.

ftp:// File Transfer Protocol

ftp://oak.oakland.edu/SimTel/ •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.

http:// HyperText Transfer Protocol

http://www.uncg.edu/~bucknall/tim/ •The protocol for transfer of hypertext documents written in HTML and JAVA.• The primary protocol for the WWW.

mailto: 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.



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://steffi.uncg.edu/ •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.



Host Domain Names• Form of host domain names:

• 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.

Service/Machine Location Domain

www uncg edu

Example: www.uncg.edu


• The domain can tell us what type of site we can expect to be visiting.

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

Common Domain Acronyms


• 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


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.


• 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.


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.


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.


Java

• General purpose object-oriented programming language.

• Based on C++, but simpler and safer.

• Focus is on applets and servlets.


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


• Perl is highly platform independent, and has been ported to all common platforms.

• Perl is not just for CGI.


PHP

• A server-side scripting language.

• An alternative to CGI.

• Similar to JavaScript.

• Great for form processing and database access through the Web.


Recent technology in web development:

• AJAX

• Java Web Software (e.g: servlets, NetBeans, JavaBeans)

• ASP.NET

• Ruby

• Rails


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

Documents

CHAPTER 1 Internet & World Wide Web. Topics A Brief Introduction to the Internet The World Wide Web Web Browsers Web Servers Uniform Resource Locator