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:

The most common Boolean operators are AND, OR and NOT (always in capitals). They can be used to get more accurate search results.

• AND narrows down the search by adding more keywords that need to appear in your results, eg The words 'black' and 'shoes' will return results that contain the words 'black' and/or 'shoes'. You may get results that contain only one of the two words, eg 'purple shoes for sale' or 'black T-shirts for sale'.
• OR widens 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 'Pirates of the caribbean'. The results will contain the word 'film' but not 'Transformers'. Some search engines use a minus sign in front of the word instead of NOT, eg - Pirates of the caribbean.
• Quotation marks although not strictly a Boolean operator, quotation marks can be used to get more accurate results. For example, use 'black boots' to get results where the words 'black' and 'boots' appear together, eg 'black boots for sale'. By doing this, the result 'black shoes and purple boots for sale' will not be returned.

Task - Research

Find out about Dihydrogen Monoxide and write your opinion about it in a word document. Click on the link below to take you to the DHMO website

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