Transcript The Internet

The Internet
Computer Studies Higher Grade
Grades 11 + 12
What is the Internet?
wake up Neo…
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A world-wide network of
Computers and
Computer networks
Connected via telephone lines or other
mediums
In order to provide certain services
To those connected to the network
http://www.exclaim.it/glossary.php?firstletter=A
What do I need to connect to the
Internet?
A computer
 A modem
 An account with an ISP
 A phone line
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A modem converts digital signals from your
computer into analogue signals that can
be transmitted via phonelines
How does the Internet Connection
work?
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Your computer connects to your ISP using
your modem and your phone-line
 Once your ISP has verified your user-name,
password and account details you are ready to
use the Internet
 You ask your ISP to get web-pages and emails for you and it does the job and sends the
data back to your computer
 Your ISP accesses information on your behalf
How?
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Web-pages are stored on web-servers all
over the world.
When you want a web-page your ISP
knows where to find it and goes and
fetches it for you.
Your browser then displays it on your
screen.
Your ISP also locates other resources such
as other e-mail servers and chat servers.
Diagram of the whole thing
Your
PC
Web-Server
YOUR
ISP
Another
ISP
Chat
Server
Web-Server
Another
PC
The other ISP is in
reality also connected
to the other servers
Still confused?
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Check these sites out:
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http://computer.howstuffworks.com/internet-infrastructure.htm
http://www.learnthenet.com/english/animate/connect.html
http://www.mids.org/what.html
Two types of connections
1.
2.
It is possible to have a permanent
connection (leased line), and this often
the situation in large business
organizations and universities
Other users use a modem that converts
digital signals of a computer to the
analogue signals required for normal
voice-carrying telephone lines
Things to do on the Internet
World Wide Web (WWW)
 Electronic Mail (e-mail)
 Newsgroups (Mailing Lists)
 File Transfer Protocol (FTP)
 Telnet
 Internet Relay Chat (IRC)
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World Wide Web
A collection of multimedia documents
connected with hyperlinks
 Largest growing area of the Internet
 Popularity is high due to it’s easy to use
interface
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World Wide Web 2
Web-sites are made up of inter-related
web-pages
 These pages are connected using hyperlinks
 Hyper-links are text or images that you
click on to display a related web-page
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World Wide Web 3
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You need a web-browser to access websites on the Internet
A web-browser is a program that displays
web-pages and their related links in a
window with an easy to use interface
 Web-browsers allow you to go back to a
previously visited page, print web-pages
and keep a list of your favourite and
regularly visited web-sites
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World Wide Web 4
Each web-site has a unique address
sometimes referred to as the URL
(Uniform Resource Locator)
 Each URL consists of various parts
separated by dots (.) or slashes (/)
 See example on next slide
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World Wide Web 5
http://www.cs.uct.ac.za/~dgruijte/index.html
http – Hyper Text Transfer Protocol… this tells the
web-browser that you’re accessing a web-site
 www – World Wide Web
 cs.uct – The domain name… usually linked to the
institution involved
 ac – Academic institution
 za – South African
 /~dgruijte/ - Location of web-page on the domain
 index.html – web-page to be viewed
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Some domains
.gov – government sites
 .org – organisations
 .com – usually big businesses
 .net – usually soley internet based
organisations or groups
 .edu – education (also .ac)
 .co.za – South Africa Site
 .co.uk – UK Site
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World Wide Web 6
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There are two ways of getting to a website
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2.
Typing the address straight into the
address-box in your web-browser
Using a search engine
World Wide Web 7
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Typing the address
into the address box
World Wide Web 8
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Search Engines
You type in what you’re looking for and the
search engine will search the web for all
web-pages related to your search
 The search engine then displays the results
as hyper-links which you can click on to
view the web-sites
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World Wide Web 9
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Many, but not all search engines allow you to use so-called
Boolean operators to refine your search. These are the logical
terms AND, OR, NOT, and the so-called proximal locators, NEAR
and FOLLOWED BY.
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Boolean AND means that all the terms you specify must appear in
the documents, i.e., "heart" AND "attack." You might use this if you
wanted to exclude common hits that would be irrelevant to your
query.
Boolean OR means that at least one of the terms you specify must
appear in the documents, i.e., bronchitis, acute OR chronic. You
might use this if you didn't want to rule out too much.
Boolean NOT means that at least one of the terms you specify must
not appear in the documents. You might use this if you anticipated
results that would be totally off-base, i.e., nirvana AND Buddhism,
NOT Cobain.
+ and - Some search engines use the characters + and - instead of
Boolean operators to include and exclude terms.
World Wide Web 10
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NEAR means that the terms you enter should be within a
certain number of words of each other. FOLLOWED BY
means that one term must directly follow the other. ADJ, for
adjacent, serves the same function. A search engine that will
allow you to search on phrases uses, essentially, the same
method (i.e., determining adjacency of keywords).
Phrases: The ability to query on phrases is very important in
a search engine. Those that allow it usually require that you
enclose the phrase in quotation marks, i.e., "space the final
frontier."
Capitalization: This is essential for searching on proper
names of people, companies or products. Unfortunately, many
words in English are used both as proper and common nouns-Bill, bill, Gates, gates, Oracle, oracle, Lotus, lotus, Digital,
digital--the list is endless.
World Wide Web Services
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The following are available on the WWW
Research and Education
 News
 Shopping
 Banking
 Games and Hobbies
 Advertising
 Communications
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Electronic Mail
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Sends messages containing text, pictures and
other media
Each e-mail address is unique
An e-mail server (usually your ISP) manages
your e-mail address for you
Web-based e-mail servers are also available
e.g. hotmail.com, webmail.co.za
When an e-mail is sent to an address the email actually gets sent to the ISP that hosts
that e-mail address and not directly to the user
Example
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Your ISP is MWeb
You send an e-mail to [email protected]
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When you click “send” the e-mail is sent to your ISP’s e-mail
server
Your ISP looks at the address and sees that the e-mail must
be sent to someone at iafrica.com
The e-mail is then transferred to the destination server
Bob checks his e-mail
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When Bob checks his e-mail his e-mail client sends a request
to his ISP asking if there is any e-mail for him
Because his e-mail is kept on the iafrica server his ISP knows
immediately if there are new messages.
These messages are then sent from iafrica.com to Bob’s pc.
Diagram
Your
PC
You send an e-mail
from your PC to
[email protected]
MWeb
Your ISP sends the
e-mail to the destination
e-mail server
iAfrica
Bob checks his
e-mail
Bob’s
PC
Web-mail
Web-mail works much the same way
 The only difference is that the e-mail
stays on the destination server
 The user has to use a web-browser to
read, send and manage those e-mails on
the server.
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Advantages of E-mail
Faster
 More reliable
 Can send to multiple people at once
 Multimedia attachments
 Cheaper
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Disadvantages of E-mail
Viruses!
 Impersonal
 Not everyone has an e-mail address
 Spam
 Spam
 Spam
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Newsgroups
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Newsgroups are places for people to post
messages of a common topic.
Any user can view the news group and read
the messages there.
The messages stay permanently on the
newsgroup and each user must check the
newsgroup for new messages.
Any user can post a message to the news
group.
Requires you to have a news-reader installed.
Mailing Lists
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A list of e-mail addresses identified by a single name,
such as [email protected]
When an e-mail message is sent to the mailing list
name, it is automatically forwarded to all the addresses
in the list.
When you subscribe to a mailing list then your e-mail
address is added.
When someone sends a mail to the mailing list then all
members of the list receive it.
You can send to the mailing list simply by sending your
e-mail to the list address.
This requires only an e-mail client and no special
software.
Internet Relay Chat
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These are more commonly known as chat
servers.
The user uses a chat client to connect to a
chat server.
Once connected to that chat server the user
can join a number of chat-rooms or channels
of interest.
When a user types a message it is broadcast
to all users currently in that room/channel.
Private chats are also possible.
http://www.mirc.co.za – Give it a try!
Telnet
A way of remotely using another
computer!
 A telnet client is used to connect to
another machine on the internet.
 You can then use that machine exactly
like you would if you were sitting right at
the machine.
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Software on the Internet
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Freeware
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Shareware
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This is totally free software that you never have to
pay for :)
Source-code is often included
Programs with limited functionality or limited time
period which you may use
Allows you to try a program out before you buy it
Upgrades
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Download upgrades for existing software
Microsoft Updates (waste of time and bandwidth)
Creating your own web-site
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You need
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Web Authoring software
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A domain name
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Dreamweaver, Frontpage, notepad
www.mykewlpage.co.za
A web-server to host your web-site on
Your ISP usually will provide the last two
items.
End
If you want more info take a look at:
http://computer.howstuffworks.com/channe
l.htm?ch=computer&sub=sub-internet