INTERNET SEARCH ENGINE
Internet search engines
Internet search
engines are special sites on the web designed to help people find information
stored on other sites. These search engines allow users to enter search items (e.g.
causes of typhoid fever), by typing a keyword, phrase or sentence and the
program retrieves a list of World Wide Web sites, or documents associated with
the search item.
Functions of search engines
There are
differences in the ways various search engines work, but they all perform three
basic functions:
1. They search the internet based on the
important words specified.
2. They keep an index of the words they
find, and where they find them.
3. They allow users to look for words or
combinations of words found in that index.
Types of Search engines
Search engines
can be divided into two types:
1. Crawler (crawler – based search engines):- crawler – based search engines such as Google and Yahoo,
compile their listings automatically. They “craw” or “spider” the web, and
people search through their listings. These listings are what make up the
search engines index or catalogue. An index is a massive electronic filing
cabinet containing a copy of every web page the spider finds.
2.
Directories (human - powered results):- directories such as open directory
depend on human editors to compile their listings. Webmasters submit an address, title, and a brief description of
their sites, and then editors review the submission. Early search engines were
mostly directories. Now, Crawlers are more common.
Examples of search engines
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s/n
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Search Engine
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Web Address
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1.
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Google
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www.google.com
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2.
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Mamma
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www.mamma.com
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3.
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WebCrawler
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www.webcrawler.com
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4.
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Yahoo! search
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www.yahoo.com
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5.
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Find.com
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www.find.com
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6.
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Gigablast
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7.
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Getlyrics
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8.
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Snap.com
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9.
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Looksmart
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10.
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Infoseek
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Year 9, this is your lesson note for week one
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