the internet computer studies higher grade grades 11 + 12
TRANSCRIPT
The Internet
Computer Studies Higher Grade
Grades 11 + 12
What is the Internet?wake up Neo…
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 computerA modemAn account with an ISPA phone line
A modem converts digital signals from your computer into analogue signals that can be transmitted via phonelines
How does the Internet Connection work?
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 e-mails for you and it does the job and sends the data back to your computer
Your ISP accesses information on your behalf
How?
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
YourPC
YOURISP
Web-Server
Web-Server
AnotherISP
Chat Server
AnotherPC
The other ISP is inreality also connectedto the other servers
Still confused?
Check these sites out:
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. It is possible to have a permanent connection (leased line), and this often the situation in large business organizations and universities
2. 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)TelnetInternet Relay Chat (IRC)
World Wide Web
A collection of multimedia documents connected with hyperlinks
Largest growing area of the InternetPopularity is high due to it’s easy to use
interface
World Wide Web 2
Web-sites are made up of inter-related web-pages
These pages are connected using hyper-links
Hyper-links are text or images that you click on to display a related web-page
World Wide Web 3
You need a web-browser to access web-sites on the InternetA 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
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
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
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
World Wide Web 6
There are two ways of getting to a web-site
1. Typing the address straight into the address-box in your web-browser
2. Using a search engine
World Wide Web 7
Typing the address into the address box
World Wide Web 8
Search EnginesYou 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
World Wide Web 9
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. 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
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
The following are available on the WWWResearch and EducationNewsShoppingBankingGames and HobbiesAdvertisingCommunications
Electronic Mail
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 e-
mail actually gets sent to the ISP that hosts that e-mail address and not directly to the user
Example
Your ISP is MWeb You send an e-mail to [email protected]
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
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
YourPC
MWeb
iAfrica
Bob’sPC
You send an e-mailfrom your PC [email protected]
Your ISP sends thee-mail to the destination
e-mail server
Bob checks his e-mail
Web-mail
Web-mail works much the same wayThe 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.
Advantages of E-mail
FasterMore reliableCan send to multiple people at onceMultimedia attachmentsCheaper
Disadvantages of E-mail
Viruses!ImpersonalNot everyone has an e-mail addressSpamSpamSpam
Newsgroups
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
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
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.
Software on the Internet
Freeware This is totally free software that you never have to
pay for :) Source-code is often included
Shareware Programs with limited functionality or limited time
period which you may use Allows you to try a program out before you buy it
Upgrades Download upgrades for existing software Microsoft Updates (waste of time and bandwidth)
Creating your own web-site
You needWeb Authoring software
Dreamweaver, Frontpage, notepadA domain name
www.mykewlpage.co.zaA 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/channel.htm?ch=computer&sub=sub-internet