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Chapter 12 (Historical Perspective 12.2 (Developing the internet (Although…
Chapter 12
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12.4
Types of search engines
Companies have developed special programs called search engines which 'read' this vast number of pages and index them, although no search engine has ever indexed everything on the internet
How search engines work
Each search engine works in different ways in an attempt to offer unique features. Some robots 'bot' programs called spiders or crawlers to tack web pages, follow lings, add information to the search engine database.
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12.8
Security
Encryption
Encryption techniques prevent unauthorised access by changing data into a form that is unreliable without a 'key'
Virus protection
Computer viruses can spread when you
- launch an infected application
-use a disk that has infected files
-download from the internet
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Equity
Not everyone has equal access to the internet and not everyone has the skill to use the sophisticated techniques needed ti efficiently access that information
Cookies
A cookie is just one or more pieces of information stored as text stings on a users computer. it is used to keep track of data needed in the future
Digital certificates
There are issued by organizations know as certificate authorities. the user requests a certificate with the users name a serial number and the issuing authority.
Certificates can then be used to verify that you are the person you claim to be
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12.1
Describing the Internet
The internet is not only one network. It consists of thousands of connected networks of varying sizes
The power of information
The internet is one of the most dramatic examples of our 'shrinking' world.
With one click it is possible to book an overseas trip check the weather before a plane flight
12.3
World Wide Web
The World wide web (WWW) is the best know part of the internet and is a network of sites that can be searched and retrieved by special protocol know as hypertext transfer protocol
Connecting
It is possible to connect to the internet in a number of different ways. Whichever method is used, the basic equipment includes a computer, some kind of data connection, software for access, an account with an internet service provider and a modem
12.6
Transfer protocols
Although we have already encountered the transfer protocol in sections 12.2 and 12.3 we will summarize them here:
HTTP is the underlying protocol used by the world wide web. It defines how messages are formatted and transmitted and what actions web services and browser should take
SMTP controls the delivery of email. most emails systems use SMTP to send messages from one server to another.
FTP is an internet protocol that allows the upload and download of files
Communication protocols
You may have heard about TCP/IP whitch every computerusig the internet needs, and imagine it to be one protocol.
12.7
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Hyperlinks
It was during the late 1960s that Ted Nelson first thought of the idea of words with attached explanations. later Tim Berner-Lee imagined that documents might be able to be linked
12.5
Browser
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Marc Anderessen who founded Netscape created Mozilla the first web browser. A browser has one central function - to interpret coding language HTML
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