Transcript The Internet: A Resource for All of Us

The Internet:
A Resource for All of Us
Chapter 8
Objectives
• Briefly describe the history of the Internet
• Explain what is needed to get on the Internet
• Describe generally what an Internet service provider
does
• Describe the rudimentary functions of a browser
• Describe how to search the Internet
• List and describe the non-Web parts of the Internet
• Explain some of the ongoing problems associated
with the Internet
Contents
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History of the Internet
URL
Getting Started
Internet Service Provider
Browser
Browser Support
Moving Between Sites
Searching the Internet
Other Uses of the Internet
Internet Issues
History of the Internet
• Government and Universities over 30 years
• Who’s connected today?
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Individuals
Educational institutions
Government
Research
Medical
Businesses
Everyone!
ARPANet
Advanced Research Projects Agency Network
• 1969 – US Department of Defense and Rand
Corporation
• Origins
– Cold War – fear that a bomb could demolish
computing capabilities
– Several computers, geographically dispersed,
networked together
– Plan – if one computer was disabled, others could
carry on using alternative communication routes
ARPANet
Transmitting the Message
• Messages divided into packets
• TCP/IP protocol
– TCP – does the packeting and
reassembling of the message
– IP – handles the addressing
ARPANet
Expands Beyond the Military
• Research computers from universities
• Defense contractors
• Needed technical expertise to work on
Internet
Tim Berners-Lee
• 1990
• Perceived a spider’s web of computers with
links from computer to computer
• CERN site
– Dr. Berners-Lee’s physics laboratory
– Birthplace of the World Wide Web
• Easy movement due to links
– Hypertext
– Hyper-region
Marc Andreessen
• 1993
• Created browser software
• Mosaic – first browser
• Provided attractive images and a graphical
interface permitting users to click on pictures as
well as text
ARPANet to Internet
• TCP/IP software is public domain
• Network became more valuable as it
embraced other networks
• ARPANet disappears
Internet Explosion
• Mid 1990s
• Estimate over 333 million users worldwide
• Part of our daily lives
• Four factors
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TCP/IP standard
Ability to link from site to site
Ease of use of browser
Growth of PC and LANs that can connect
URL
Uniform Resource Locator
http://domain-name.top-level-domain/last-section
• Unique address of a web page or file on the
Internet
• Case-sensitive
http
hypertext transfer protocol
http://domain-name.top-level-domain/last-section
• Protocol – rules
• Communication using links
Domain name
http://domain-name.top-level-domain/last-section
• Address of the ISP
• Domain names are registered
• Ongoing fee is paid for each domain name
Top-level Domain
Represent the purpose of the organization of entity
.com
.gov
.edu
.org
.net
May be a two-letter country code
Last section
http://domain-name.top-level-domain/last-section
Directories and file names that specify a
particular web page
Getting Started
• Computer with a modem or NIC
• Internet service provider (ISP)
• Browser
• Related software
Internet Service Provider
• Vehicle to access the Internet
• Provides
– Server computer
– Software to connect
Online service
• ISP
• Members-only services and information
• Simple interface with clickable topics
• Parent controls
Wireless Internet Access
• Supports mobile handheld devices
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Text pagers
PDAs
Pocket computers
Web-enabled cellular phones
• Applications
– E-mail
– Checking weather
– Making airline reservations
Wireless Internet Access
• Need
– Account with wireless access provider
– Cellular modem card or adapter
• Wireless Application Protocol (WAP)
– Convert web pages into format for mobile devices
– Resized for limited display area
– Fewer graphics transmitted
• Slow download speeds
Browser
Netscape Communicator
Microsoft Internet Explorer
Browser
• Used to explore the Internet
• Dials the ISP
• Display web pages
Browser
Parts of the screen
Browser
Functions and Features
• Browser display window
– Displays contents of web page from each Internet
site visited
– Screen limits how much of the site you can view at
a time. The page can be scrolled using the scroll
bar to see its entire contents
• Status line – progress of data being
transferred and other messages
Browser
Functions and Features
• Welcome banner on title bar
• Browser logo – animation indicates you are in
the process of moving to a new site
• Hot list
– Bookmark
– Favorites
– Store your favorite URLs
• Browser control panel – menus and buttons
Browser
Menus and Buttons
• Pull-down menu
• Buttons
– Convenient shortcuts for commonly used
functions
– Click button rather than locate command
from pull-down menu
Browser Support
Frames
• Divides page into rectangular sections
• Each section displays web pages independently
• Several small pages on one screen
– Can be scrolled independently
– Can be replaced with other pages independently
Plug-ins
• Software that increases the functionality of a
browser
– Audio-video
– Image viewing
• Download from web sites
• Install
• Example
– Adobe Acrobat Reader
– Shockwave
Programming
Java
• Write software that is machine independent
• Programming language
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Dancing icons
Sound clips
Flashing messages
Banners that scroll
• Applets – Permits dynamic web pages
– Display animations
– Receive input
– Perform calculations
Programming
ActiveX Controls
Capabilities similar to Java
Browser must be enabled to support
applets / ActiveX Controls
Security issues
Moving Between Sites
• Clickable categories in the browser
– Sports
– Weather
– News
– Technology
– Comic strips
• Enter the URL in the address text box
and press <Enter>
Processing Requests
URL
• User enters a URL
• User computer sends request to the ISP
server
• ISP server sends request across networks of
TCP/IP computers
• Destination site is reached
• Content is transmitted back to your computer
(process in reverse)
Searching the Internet
Search engine
• User specifies a search request
• Browser links to Search Engine
• Request returns matching pages based
upon the Search Engine’s database
• Results presented
Processing Requests
Search Engine Database
• Search Engine builds database
– Searchable terms
– Related web sites
• Spider, robot, bot
– Follows links across the web
– Automatically indexes pages to a database
• One word
• All words
• Pages may be submitted by the owner
Processing Requests
Search Engine Database
• Request same search using different engines
yields different results
• Databases built independently
– Size
– Content
– Search methodology
• Metasearch – atomically puts the same
request to several search engines
Processing Requests
Directory vs. Search Engine
• Directory
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Human involvement
Sites organized by content category
May concentrate on specific content areas
Subjective decisions regarding inclusion and
importance
• Search Engine
– Spider, robot, or bot automatically builds database
– Index on a few keywords
– Index on all words on web page
Processing Requests
Search Engine Limitations
• Index only a fraction of the Web
• Approximately 20% to 33% of sites
• More web pages added daily
• Solution
– Same request to several search engines
– Metasearch
Search Tools
Directories
Search Engines
• Yahoo!
• AltaVista
• NetGuide
• Excite
• Google
Metasearch Sites
• HotBot
• MetaCrawler
• Infoseek
• Dogpile
• Lycos
• Northern Light
Refine the Search
• Add words
• Enclose words in “quotes”
• Use Boolean logic
• Examples
– “World Trade Center”
– Jordan AND NOT Michael
Other Uses of the Internet
• Newsgroups
• FTP
• Telnet
• E-mail
• Internet Relay Chat (IRC)
Newsgroups / Usenet
• Large bulletin board divided by category
• Posting and reading of messages that focus
on specific topics
• Over 20,000 newsgroups
• Functions
– Conversation
– File download
• Newsreader software required (included
with most browsers)
Newsgroup Operations
• Lurking
• Posting material
– Inappropriate material
• Flame
• Flame war
– Moderated newsgroup
FTP
File Transfer Protocol
• Download files to your local computer
• Upload files to another computer
• Requirements to download file
– Permission to download from a site
– File is available for copying
• Anonymous FTP – do not need to identify
yourself to the remote computer
Public Archives
Free files provided by educational
institution or the government
Telnet
• Use your PC as a terminal providing remote
access to another computer
• Permits
– Log on to a host
– Use as if you are sitting at a local terminal
• Need account on the host system
• Telnet software required (provided with most
browsers)
e-mail
• Send/receive written messages
• Most used feature of the Internet
• Mail server – Collects and stores e-mail
• Mailbox – Assigned to each user
• E-mail address
– User name
– @
– Domain of the mail server
e-mail
Client Software Functions
Retrieve
Print
Create
Delete
Send
Address book
Store
Attach files
Filters
IRC
Internet Relay Chat
Not Quite Perfect Yet
• Unregulated
• Useless web sites
• Misinformation and misstatements on web
sites
• Concern over government censorship
Not Quite Perfect Yet
Social Issues
• Behavior problems
– Who is out there?
– What are they doing?
• Netiquette
– Suggestions for appropriate behavior
– Example: TYPING IN CAPS is shouting