Chapter 2

cowphysicistInternet και Εφαρμογές Web

4 Δεκ 2013 (πριν από 3 χρόνια και 6 μήνες)

105 εμφανίσεις

The Internet & the World Wide
Web

Chapter 2

Exploring Cyberspace


Chapter 2: Key Questions

2.1 What are the means of connecting to the Internet, and
how fast are they?

2.2 What are the three types of Internet service provider,
and what kinds of service do they provide?

2.3 What are the components of an e
-
mail address, and
what are netiquette and spam?

2.4 What are Web sites, Web pages, browsers, URLs,
and search engines?

2.5 What are FTP, Telnet, newsgroups, real
-
time chat,
and e
-
commerce?

To Access the Internet, You Need



An
access device


A
physical connection


An
Internet Service Provider (ISP)


Can you give examples of each?

Physical Connection


Telephone (dial
-
up) modem


Several high
-
speed phone lines


ISDN


DSL


T1


Cable modem


Wireless

Data Transmission Speeds


Upload


data from local computer to remote


Download


data from remote to local


Bandwidth


Data that is sent through a communications channel in a given
amount of time


Data transmission speeds:


Bps


bits per second




Kbps


kilobits per second


Mbps


megabits per second


Gbps


gigabits per second


8 bits = 1 byte = 1 character

Telephone Modem

High Speed Phone Lines


ISDN (Integrated Services Digital Network)


Hardware & software


Uses traditional telephone lines
(128 Kbps)


DSL (digital subscriber line)


Always on


Transmission rate is consistent
(1.5
-
8.4 Mbps)


Must live within 3.3 miles of a phone company switching office


T1 line
(1.5 Mbps)


Used by corporate, government, and academic sites

Cable Modems


Connects a PC to a cable
-
TV system that
offers Internet access


Always on


Competes with DSL


Transmission rate may not be consistent
during peak hours


Speed:10 Mbps

Wireless Systems


Communications satellite


Radio waves (microwaves) transmitted from earth
-
based stations


Receives data at 400 Kbps & sends data at 56 Kbps
(with phone line)


Other wireless connections


Radio waves for cellular phones


Sends data up to 155 Mbps



Three Types of ISP Services


Free
-
service providers


NetZero, AltaVista, BlueLight.com


Advertisements and personal info


Basic
-
service providers


Offer local connection


Full
-
service providers


AOL, Earthlink, MSN


More technical support and international access


How to Get E
-
mail Software?


Purchase


MS Outlook express, Lotus Notes


Get as a part of other package


Netscape Communicator


Provided by your ISP


AOL


Free Email Services


Yahoo, Hotmail

E
-
mail Addresses

Joe_Black@earthlink.net.us

User ID

Domain Name

Domain Top
-
level domain Country

(location) (domain type)

E
-
mail


Attachments


Attached to emails


Formatting preserved


Recipient must have software to read them


Instant messaging


Cross between e
-
mail and phone


Message pops up instantly on the screen if user is
logged on

Netiquette


Use FAQs


Avoid flaming


Don’t shout


Avoid sloppiness


Make attachments small




Quote only relevant
portion when replying


Avoid spams

World Wide Web


Uses of the WWW


E
-
mail


Entertainment


E
-
commerce


E
-
tailing, auction, online finance, on
-
line job hunting, B2B


Why the WWW is inviting & easy to use


Multimedia format : graphics, video, audio, text


Use of hypertext

Web Terms


Web site


a computer with a domain name is called a site


Web pages


a document that can include text, pictures, sound, and video


Browsers


software that enables users to view Web pages URLs


URLs (Universal Resource Locator)


a string of characters that point to a specific Web page


Web portals


Web sites that group together popular features

Web Terms


Multimedia format


graphics, video, audio, text


HTML (
hypertext markup language)


A language used to specify document structure,
formatting, and links to other documents


HTTP



hypertext transfer protocol

rules that allow
browsers to connect with Web servers


Search Engine Types


Human
-
organized search sites


subject experts (humans) do the indexing


Yahoo!. AOL, MSN, Netscape, Lycos


Computer
-
created search sites


software "spiders" (software) do the indexing


Northern Light, Excite, WebCrawler, FAST Search, Inktomi


Hybrid search sties


humans supplemented by computer indexes


AskJeeves, Direct Hit, Go, GoTo.com, Google, HotBot, Snap


Metasearch sites


sends query to other search tools and compile the results


Go2Net/MetaCrawler, SavvySearch, Dogpile, Inference

Multimedia on the Web


Plug
-
ins & helper applications


Multimedia development


Applets, Java, JavaScript, ActiveX


Text and images


Animation


Video


Audio

More Internet Resources


FTP


File Transfer Protocol


a program that can transfer files to one compute to another


Telnet


a program that allows you to connect to remote computers on
the Internet


Newsgroups


a giant electronic bulletin board on which users conduct written
discussions about a specific subject


Real
-
time chat


participants have a typed discussion while online at the same
time