Such computer programs are called search engines, which seek information from the information stored on a computer system. These engines often offer results as a list that reveals the nature and position of the desired information. Search engines help us to reach a notice in a relatively short period of time. They also save us from 'information overload'.
The most popular form of a search engine is 'Web Search Engine', which is used to find information on the World Wide Web.
A search engine operates with the following command
Web search engines work on the basis of information stored in many web pages that retrieve their WWW. These pages are obtained by web crawler and (sometimes known as spider); An automated web browser that looks at every link can be redressed using robots.txt (robots.txt). An analysis of the content of each page can be determined by how it is indexed (for example, The word is attached to titles, specimens, or special fields called meta tags) for subsequent inquiries stored in the base content data index in web pages for subsequent inquiries. Some search engines like Google store some parts of the source pages or as part (cache) as well as information about web pages while others like AltaVista each word of each page There are also plates that store them. This cached page is always holding the actual search text since it has been listed in the original form, so when it is updated to the content of the current page and it will not be too long after searching the content it can be extremely useful. This problem of linkrot should be understood lightly and its usage in Google's operations is increased because it has given the search terms the return of web pages. Wind satisfies users' expectations. It satisfies the principle of minimum astonishment. Usually the user expects search results on the returned pages; Consolidated pages are increasing by increasing the relevant search. Useful, even data from outside of these facts can be any which is not available anywhere.
When a user enters the query in the search engine (usually using the key word), the search machine examines its index and indexes the appropriate web pages according to its criteria. Usually, with a short summary that is based on the parts of the document and the parts of the text, mostly search engine bullion operators AND, OR and NOT to calm down the search query Area to catch support. Some search engines provide advanced types of operators, which are called proximity search, which help the user define distances of keywords.
Utility (relevance) of this search engine is based on the suitability of its results. Although there are millions of web pages that contain special words or phrases, some pages may be more relevant, popular, or more authentic than others. Most search engines adopt such methods that their results are "best" and the first is how a search engine decides which page is most appropriate and from which many other engine engines Should show. Changes are also taking place over time as the use of the internet is changing and new technology is evolving.
Most web search engines are supported by business entrepreneurial income. As a result, some controversial methodology allows advertisers to earn the highest position/category in search results, depending on the payment of money. Those search engines who do not accept money for the results of their search make money with search related results running with search engine results. When someone clicks on any of their ads, the search engine makes money every time.
Most search engines are run by private companies and they use algorithms and closed data sets. However, some (some) are public sources.