Search engines

The internet is a fantastic tool that helps you to learn, to share, to communicate and to find entertainment. It has billions of pages filled with information, in the form of words, images, videos and sound. Finding the information you need from these billions of pages can be tricky. If you had to look through each page, it would take many years to find the information you seek. Search engines make the task much simpler.

Search engines are programs that are designed to search the internet for us. They scour through all the billions of webpages, looking for information that matches what you are seeking. By using a search engine you can find information in seconds.

Finding information without using a searching algorithm can take a very long time. By using a searching algorithm, information can be found a lot quicker.Search engines quickly find relevant information from billions of webpages

How search engines work

When you use a search engine to find information, you type in a search term which consists of one or more keywords that are specific to the information you seek. For example, if you wanted to learn more about how to eat healthily, your search term might include the keywords ‘eating’ and ‘healthily’. The search engine would look through all the webpages on the internet and create a list of links (or results) to all pages that contain these keywords. The list is sorted into order, with the most popular (or most visited) results at the top. You can then choose to follow any of the listed links and websites to see what information they contain.

Search engines such as Google use very complex page ranking algorithms to decide the exact order in which results should appear. The biggest factor is the number of sites linking to that web page.

Refining searches using Boolean expressions

Keywords are used to tell a search engine what information you are looking for. However, the resulting list of websites a search engine returns is often not quite what you want. Boolean expressions, such as AND, OR and NOT, allow you to make your search terms more specific.

Suppose you live in Manchester, and want to go to the cinema to watch a film. You might search for this information using the search term ‘films’. This would generate millions of results, because the keyword ‘films’ is very common – lots of websites would mention that word.

Boolean expressions, such as AND, OR and NOT, allow you to refine your searches further:

  • AND narrows down the search by adding more keywords that need to appear in your results, eg ‘film’ AND ‘Manchester’. The results will contain both these keywords.
  • OR widen the search by including alternate words, eg ‘film’ OR ‘movie’. The results will contain either of these words.
  • NOT excludes certain information, eg ‘film’ AND NOT ‘Transformers’. The results will contain the word ‘film’ but not ‘Transformers’.

Using these expressions often gives you a better chance of finding what you are looking for.