May 5, 2013

SEARCH ENGINES

Definition :
A search engine is a program that searches through a database of web pages for particular information.


                            Until now, you were surfing internet by visiting sites known to you. What if you want to view particular information, but you do not know which site would provide you that information. In that case, you need to search for that information on the web. And this can be done through search engines, a program used for searching information on the internet.

SOME POPULAR SEARCH ENGINES :
www.Google.com
www.Bing.com
www.Yahoo.com
www.Ask.com
www.Duckduckgo.com
www.Dogpile.com
www.Blekko.com
www.Aol.com
www.Webopedia.com
www.Altavista.com
www.Teoma.com
www.Entireweb.com


Search Engines

FINDING INFORMATION USING A SEARCH ENGINE :
There are many search engines on the web.The searching process is similar on these search engines. To search for web pages pertaining to a specific information, all you have to do is .............

1. Go to the home page of the search engine.
2. Type the information to be searched for in the box provided for it.
3. Now click at Search button next to it. Within a few seconds, the search engine will search for that information and display the links to the web pages, which are linked to your desired information in some way.

HOW SEARCH ENGINE WORKS :
In a search engine, you can type keywords to search for and a search engine searches them, on the web and provides you the details. A search engine works with the help of following three elements.

1. Spiders or Webcrawler or Bots or Agents : The search engines use a software called spider or webcrawler or Robot or bot or Agent which comb the internet looking for documents and their web addresses. The spiders or webcrawlers perform the methodical searches needed to find information.

                         The bots or spiders are given direction by the search engine and they crawl from one server to another, compiling the huge lists of URLs (based upon the directions) given by search engine.

2.Indexing Software and Database : The lists of documents and web addresses collected by bots are sent to the indexing software. The indexing software extracts information from the documents and web addresses, prepares on index of it and stores in a database.

                          The kind of information indexed depends upon the particular search engine. Some index every word in the document, others index the document title only.

3.Search Algorithm : When you perform a search by entering keywords, the search engine software searches its database (in which indexing software stores its entries) using a particular search method called Search Algorithm. And then it displays the matching documents or web addresses.

SOME SEARCHING TIPS :
To effectively search for desired information, you must learn the art of framing search queries. in the following lines, we are going to discuss some tips for the same..............

1. Do not ask questions. For example, if you want to find out some information about home minister of India and if you type in the search box, then you may end up getting lakhs of matches but most being useless.
                          
                              This is because the search engine searches for each word in the search query separately. That is, in this case, your search will search for words "who", "home", "minister", "India" separately and then display all the results. Common words like "a", "and", "is", "the" etc. are dropped.

2. Surround your query in quotes or put some punctuation marks (, . ; - ) if you want it to be treated as single phrase rather than a series of individual search terms. For example, if you want to search for the book titled God of Small Things then you may write it as
                       "god of small things"
   or as              god-of-small-things
   or as              god ; of ; small ; things

3. Use wildcard * for pattern matching. For instance, if you want to search for certain things starting with dir, then you may write

                 dir*

In the search box and your search engine will search for many words starting with dir . Example: dire, direct, direction, directive, director etc.

4. The lowercase word matches are not case-sensitive but uppercase words are case-sensitive for example, if you write

                           program

It will match with program or programs or PRogram ....... and PROGRAM .

But if you write

      PROgram

Then it will match PROgram only.

5. To specify that a word or phrase must appear in matched documents, put a plus sign (+) immediately before it. For example, the following query

+boston +university

Will match with web pages having both the words boston and university.

6. To specify that a word or phrase must not appear in matched documents, put a minus sign (-) immediately before it.

Example:
                    +asia-china


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