What are Search Engines?
Search engines are programs that search document for
specified keywords and return a list of document where keywords were found.
These are designed to search for information on World Wide
Web. The search results generally presented in a line of results referred to
SERP (search engine results page).
Search engines are very critical key element to find out
specific and relevant information through huge extend of World Wide Web.
For example: google, yahoo, bing, msn etc
How Search Engine works?
Search engines have robots (spiders, crawlers) that scour
the internet and send back the results and links to the search engines. Usually
a webpage may have pdf, jpg, image or other files, but search engines need to
crawl all types of webpage so they use the best paths-links.
There are total five steps of working:
Crawling:
First of all search engines crawl the web to see what is
there on webpage. So a piece of software called robots crawl the whole webpage
and follow links from one page to another. Crawlers can reach millions of
interconnected documents following links.
Spider (robots, crawler):
A set of computer
program that browses www in methodical way and automatically scan the webpage
& website for updated content & downloaded a copy of its data centre to
index.
Every search engines have their robots like google has
googlebot, yahoo has yahoo slurp and bing has bingbot etc.
Indexing:
The process of indexing is identifying the words and
expressions that describe the page and assigns the page to a particular
keyword.
After search engine index everything they found on the way
according to their relevancy and important links. And indexed page is stored in
a giant database from where it can later be retrieved.
Processing:
When visitors enter for a search query, the search engine
processes it. They compare the search request with the indexed pages in
database. They search the relevant information from their database as we search
meaning of a specific word from the dictionary.
Calculating Relevancy:
It might be possible that more than one page contains search
string. So search engines starts calculating relevancy of each page according
to their unique contain and important links. They calculate relevancy with the
help of various algorithms like keyword density, links, Meta tags etc.
Websites with unique and updated contents get higher
preference than others.
Retrieving:
After choose pages for search query, they display the
results in the browser with most important sites to least important sites.