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The Internet and the The Internet and the World Wide WebWorld Wide Web
The Internet and the The Internet and the World Wide WebWorld Wide Web
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What is the Internet?
• A collection of networks (LANS and WANS) around the world that can to communicate with each other
• The physical infrastructure or backbone is made up of:– Computers– Cables– Satellites
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The Global Network
Satellites
Computers
Cables
Servers
Users
ISPs
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WWW Structure
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What is The Word Wide Web (WWW)?
• The URL or web address uses a set of protocols that allows different types of computers and operating systems to ‘talk’ to each other
• The URL is a ‘translating’ device
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Hypertext
• Hypertext is the code used to prepare pages for viewing (HTML tags etc)
• Hypertext links are placed throughout web pages that allow the user to jump from place to place (site to site)
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Browser
• The Browser is the software used to explore the internet– Internet Explorer (Microsoft)– Netscape Navigator (Mark
Andreesen)
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Protocols
• Are the rules followed to communicate over the WWW– http – hypertext transfer protocol– URL – Uniform Resource Locator– FTP – File transfer protocol– TCP/IP – Transmission Control
Protocol/ Internet Protocol
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URL – Uniform Resource Locator
• A URL or Web Address is made up of a number of parts
• It represents the unique address of an internet site or file
http://http://www.intel.com/pressroom/links.htm
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ISP – Internet Service Provider
• A company that provides access• A monthly fee (or sometimes free) gives
you– The necessary software package– A username and password– An access phone number
• Equipped with a modem, you can then log on to the internet and browse the WWW and send and receive emails
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Web Server
• This is a very large computer which holds website files
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HTTP• HTTP (Hypertext Transfer Protocol)
– It transports ‘hypertext’ documents over the internet
– The user enters an address (URL) in the browser, which identifies a file on a web server
– The file is located, sent to the users computer and interpreted by the browser, after which it can be displayed on the screen
http://http://www.intel.com/pressroom/links.htm
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HTTP
• With HTTP the file itself is not sent to us – only a copy that is held in the browser’s ‘cache’ or temporary memory
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IP Address• Every computer connected to
the internet needs an IP address– Example (234.208.12.129)
• For intuitive reasons these are often replaced by Domain Names such as intel.com or microsoft.com
http://www.intel.com/pressroom/links.htmpressroom/links.htm
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The URL
In order to find a particular file the system needs to know the path, folder, and file name of what is being requested (its exact location on the server)
http://www.intel.com/pressroom/links.htmpressroom/links.htm
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FTP
• We use FTP (File Transfer Protocol) to ‘download’ files from a web server to our own computer
• If we want a permanent copy of a file from the internet stored on our computer we must use FTP
• FTP is also used to ‘upload’ files to a web server
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Downloading Files
•We need to consider copyright issues before downloading and using files from the internet
•Viruses can infect your computer from downloaded files or emails
•Lots of files - programs, text, graphics, images, even sounds - are available to be copied without restriction
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TCP/IP
• Transmission Control Protocol / Internet Protocol
• Controls all traffic on the internet• A standard method for transferring
data
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TCP/IP
• ISPs have fixed IP addresses but ordinary users will have dynamic IP addresses
• A large file is broken up to be transported across the internet
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TCP/IP - a two-layer program
TCP • Breaks messages into smaller
‘packets’ for transmission• Ensures that all the bits are put
together at the other end
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IP
IP • Handles the address part of
each ‘packet’ so that it gets to the right destination
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People
• Tim Berners-Lee– developed the system of hyper-
linking• Mark Andreesen
– developed the first web browser
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Factors leading to Growth of the WWW
– Fall in cost of computers – Smaller computers– Development of protocols and
standards– Hypertext – clickable links– New web browser software– Growth in networking – LANs and
WANs
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Uses of Internet
• E-mail• E-commerce/Shopping• Making Bookings (travel)• Research/Education• News• Chat/Entertainment
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Today
• About 4.3 billion IP addresses at present
• Millions spent every day online• Millions do business and
communicate every day over the ‘net’
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Reading
From S: drive•Domain Names•Brief History of the WWW•Lecture NotesComputers – Tools for an
Information Age by H L Capron and J A Johnson Ch 8