Transcript Lecture - Available courses

Computer Fundamentals 1
Computing Fundamentals 1
The Internet
1
Computer Fundamentals 1
What is the Internet?
• A global network connecting millions of
computers (from more than 100
countries).
• Used to exchange data, news and
opinions, as well as perform electronic
business
• Each computer that is connected to the
internet is called a host and is
independent
2
Computer Fundamentals 1
Internet Design & History
• Internet was designed by the US Military
1960’s
• In-built multiple redundancy
• If data can’t get down one link, it will try and go
around the problem
• Wider academic use occurred later
• 1980’s uniform protocols developed
• 1990’s widespread take-up of the technology
3
Computer Fundamentals 1
Capabilities of the Internet I
• Communicate
•
•
•
•
•
Email
Usenet (worldwide discussion groups)
Chat (live and interactive discussions)
Mailing Lists
Telnet (means of remotely accessing a
computer from any other computer on the
Internet
4
Computer Fundamentals 1
Capabilities of the Internet II
• Retrieve
• File Transfer Protocol (FTP) – allows
connection to a computer on the Internet and
transferring files from it to your computer
(also allows uploads, but this requires
account information)
• World Wide Web (WWW) – websites and
web pages: billions of pages of information
stored on the internet
5
Computer Fundamentals 1
What is the difference between an
Intranet and the Internet?
• An intranet is a network that is accessed
by the people within an organisation
• Intra means ‘on the inside, within’
• Will essentially refer to the local part of the
network that is separated from the internet
by a firewall, router etc.
• The internet refers to the whole
worldwide publicly available network
6
Computer Fundamentals 1
Types of Internet Data
• Text
• Hypertext Mark-up Language (HTML)
• Web pages
• Internet Relay Chat (IRC)
• Chat rooms
• Newsgroups
• Emails
• Multimedia (images, sound, animation)
7
Computer Fundamentals 1
Internet Addresses
• Each computer has an IP (Internet
Protocol) address
• IPv4 comprised of four groups of up to
three numbers (1-255) separated by dots
• Example:
193.60.77.235
• IPv6 – Eight groups of four hexadecimal
digits.
• Example:
2001:0DB8:85A3:0000:0000:8A2E:0370:7334
8
Computer Fundamentals 1
Domain Names
• IP addresses is the basis for
transmission
• Names given to be more user friendly
• Servers can resolve between domain
names and IP addresses from local lists,
or if name or number not listed a global
list from a DNS (Domain Name Server)
• Example of a domain name
greenwich.ac.uk
9
Computer Fundamentals 1
Domain Name System hierarchy
Sample of the
Domain Name
System hierarchy,
starting from the root
“.“
Each domain name is composed of one or more labels e.g.
• Country: .de = Germany, .uk = United Kingdom
• UK company e.g.: .co.uk
• Commercial organisation e.g.: sun.com
The list is endless
10
Computer Fundamentals 1
Top-level domain (TLD)
• Top-level domain names allow us to identify the
type of domain
• .com = commercial operation or business (usually US
sites, but not necessarily).
In some countries (including the UK) .co is used instead of
.com
• .org = organisations – charities, professional associations
that operate on a non-commercial basis
• .edu = educational institution, normally universities
In some countries (including the UK) .ac is used instead of
.edu
• .gov = government
• .net = internet service provider (ISP)
11
Computer Fundamentals 1
Domain Name Example
• www.gre.ac.uk
• A site in the United Kingdom (.uk)
• Educational institution (.ac)
• “gre” is the name or abbreviation
representing the institution’s web space
• “www” denotes a web server
12
Computer Fundamentals 1
Subdomains
• No real limit to number of sub-domains
• address is read right to left (i.e.
subdomain.domain.com)
• Each domain knows the location of it’s
sub-domains
• e.g. java.sun.com – java is the
subdomain which is part of the root
domain sun.com
13
Computer Fundamentals 1
Accessing the Internet
• Computer connected directly through a
permanent connection (e.g. Intranet connected
to Internet)
• Modem that dials an Internet Service Provider
(ISP) eg. BT, FreeServe
• Access bandwidths:
• Standard connection (up to 57,600 bps)
• ISDN (64,000 bps – 1.5 Mbps)
• ADSL (1.5 – 9 Mbps)
14
Computer Fundamentals 1
World Wide Web (www)
A system of Internet servers that supports
specially formatted documents
• Originally a text based service,
developed into graphical system
• Cross-platform
• Low bandwidth (quick to load!)
• Fastest-growing part of the Internet
15
Computer Fundamentals 1
Internet ≠ World Wide Web I
• The Internet and the WWW are not the
same
• The Internet is a massive network of
networks, a networking infrastructure.
• The World Wide Web is a way of
accessing information over the medium
of the Internet. It is an informationsharing model that is built on top of the
Internet.
16
Computer Fundamentals 1
Internet ≠ World Wide Web II
• Examples of other Internet uses:
• FTP – File Transport Protocol, used to
transfer files directly between computers
• SMTP – Simple Mail Transport Protocol,
used to send emails
17
Computer Fundamentals 1
Web Pages
• Interconnected electronic documents
• Actually text files
• Contain formatting tags to define
• Formatting
• Images
• Links to other pages (hyperlinks)
• Other variations exist (XHTML)
18
Computer Fundamentals 1
Example of a HTML file
<html>
<head>
<title>Hello World HTML example</title>
</head>
<body>
<p>Hello world</p>
<img source="img/HelloWorld.gif">
</body>
</html>
19
Computer Fundamentals 1
Viewing Web Pages - Browsers
• To view web pages a browser is required
• A browser interprets the web page and
displays it
• Examples of browsers:
•
•
•
•
•
Internet Explorer
Google Chrome
Netscape Navigator
Firefox
Opera
20
Computer Fundamentals 1
Security
• By default information is transmitted as sent
• Possible to examine packets passing through the
internet and read contents
• Methods available for encryption
• Secure Sockets Layer (SSL)
• Address is https:// rather
than http://
• Also look for the yellow
padlock icon. It is
recommended that you don’t
supply details such as your
credit card number if this is
not showing
21
Computer Fundamentals 1
Favourites
• Web addresses of pages that you visit often can be
stored, by adding them to the Favorites list.
• Can be organised into folders
Favourites
To add a page to Favorites in IE:
1.
Choose Favorites /Add to
Favorites from the menu
Or:
2. Click on the Favorites icon
from the tool bar and then
click “Add to favorites”…
22
Computer Fundamentals 1
History
• The addresses of the web
pages you visit are stored
on the computer in the
History folder for a certain
period of time.
• It is expressed in days, from
0 to 999
• It can be changed by going
to:
Tools > Internet options >
Browsing History Settings
23
Computer Fundamentals 1
Temporary Internet Files
• The web pages you visit, including images, sounds,
animations, etc. are stored in locally on the computer in
a Temporary Internet Files folder.
• Storing the files locally means that they don’t have to be
downloaded from scratch every time you visit the page.
• Go to Tools > Internet Options > Browsing history… to
delete or change the Temporary Internet Files settings
24
Computer Fundamentals 1
Task for next week:
In preparation for your coursework:
• You will be writing about a famous person of
your choice
• All students please email me the name of the
famous person that you intend to write about
• [email protected]
• Sports personalities and actors are not allowed
i.e. Michael Jordan, Jackie Chan, Mohammed
Ali, Paris Hilton, Sachin Tendulkar, Wasim
Akram and Steven Gerrard etc.
25
Computer Fundamentals 1
Choose from one of the following:
A writer
A composer
A painter
A mathematician
A philosopher
A physician
A chemist
An economist
A geologist
An astronomer
An anthropologist
A botanist
A zoologist
An inventor
An architect
A computer scientist
A sociologist
The course web page is:
http://moodlecurrent.gre.ac.uk/course/view.php?id=2160
26