Transcript The World Wide Web

World Wide Web
World Wide Web
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The World Wide Web is a system of
interlinked hypertext documents
accessed via the Internet
With a web browser, one can view
Web pages that may contain text,
images, videos, and other
multimedia and navigate between
them using hyperlinks.
World Wide Web
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These documents are hypertext
documents which can contain built-in
applications, links to databases, text,
pictures, sounds, graphics, animations
and movies.
World Wide Web (www)
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These documents are written in a Web
authoring language.
The simplest language is called HTML
(HyperText Markup Language). The
documents are therefore saved as HTML
type (index.html)
The World Wide Web also uses a set of
rules (protocol) that govern how
documents written in HTML are displayed.
This protocol is the HyperText Transfer
Protocol (HTTP)
Browsers
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A turning point for the World Wide
Web began with the introduction of
the Mosaic web browser in 1993, a
graphical browser developed by a
team at the National Center for
Supercomputing Applications at the
University of Illinois at UrbanaChampaign.
This allowed the distribution of
images and the standard text-only
format from previous browsers.
Protocols
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The computers that run and are
attached to the internet must follow
a set of rules of communication so
they can exchange information.
These rules are called protocols,
which essentially set the standard for
computer communication.
Protocols may be found in software
and/or hardware.
URLs
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URL Definition:
A URL (Uniform Resource Locator)
is defined as the absolute address
of a web page or web resource on
the Internet.
URLs
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URLs can be divided into three main
parts
• PROTOCOL + DOMAIN NAME + PATH or
FILE
• Example:
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http://www.globeandmail.com/index.html
In this example we have the following:
Protocol: HTTP
Domain Name: globeandmail.com (the
www is assumed)
Path or File: index.html
Domain Name System
Domain Name
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What is a Domain Name:
• strings of letters and numbers
(separated by periods) that are used to
name organizations and computers and
addresses on the internet
• a unique, case-insensitive, name,
consisting of a string made up of
alphanumeric characters and dashes
separated by periods.
Domain Names
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The Domain Name System maps to IP
numbers and other information; an
identifier of a computer or site on the
Internet.
IP Address are unique number (like
telephone numbers) that are assigned to
computers or devices on the network or
internet.
The Domain Name System transfers the
Domain Name to the correct IP Address so
that the Domain Name can be found on
the internet
Domain Name System
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Within a domain name, there are
various levels.
• Example 1: www.globeandmail.com
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com is the Top Level
globeandmail is the Second Level
• Example2:
www.invest.globeandmail.com
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com is the Top Level
globeandmail is the Second Level
invest is the subdomain
Subdomains
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Subdomains are created by the owner of a
domain to create more address on the one
address.
For example, www.globeandmail.com may
want separate sections for
• Autos, Investing, Entertainment and sports
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Rather than having for different domains,
they will create subdomains as:
• autos.globeandmail.com,
investing.globeandmail.com and so on.
Common Protocols
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TCP/IP – used to connect to a network,
the Transmission Control Protocol/Internet
Protocol is used for packet distribution, to
acquire an Internet Protocol Address (IP
Address)
HTTP – the Hyper Text Transfer Protocol is
a request/response protocol between the
client and the server in requesting web
documents
Common Protocols
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FTP – the File Transfer Protocol is
used to exchange (send and receive)
documents over a network and to
manipulate documents residing on a
server
SMTP – Simple Mail Transfer Protocol
is used to set the guidelines that
computers must follow to send and
receive emails