Boolean Logic (Digital)

Computers can make decisions using logical or boolean operators: Not, And, Or, and Exclusive Or.

Named after the nineteenth-century mathematician George Boole, Boolean logic is a form of algebra in which all values are reduced to either TRUE or FALSE. Boolean logic is especially important for computer science because of the binary numbering system in which each bit has a value of either 1 or 0. Another way of looking at it is that each bit has a value of either TRUE or FALSE.

Boolean Operators

x AND y Result is TRUE if both x and y are TRUE. Otherwise the result is FALSE.

Television AND Violence

All web pages about television violence.

x OR y Result is TRUE if either x or y is TRUE. Otherwise the result is FALSE.

Television OR Violence

All web pages about television, and all web pages about violence.

x XOR y Result is TRUE only if x and y have different values. Otherwise the result is FALSE.

TV, Television OR Violence

All web pages about TV, about Television and about Violence

NOT x Result is TRUE if x is FALSE. Result is FALSE if x is TRUE.

Television AND Violence NOT News

All web pages about television and violence, but not violence on the news.

Search engines operate using Boolean Operators to find and filter web pages according to your instructions. For example, if you were to search the web for all cites concerning television, your search results would number in the thousands with results such as Television, Telvision in New Jersey, Television Parts, Television Plays, etc. etc. Obvisouly this type of search would not be time effective: producing more frustration than useful information. However, if you were to type in "television and violence" using the boolean operator "x AND y" your results would be significantly less because you have narrowed your search paramaters. Moreover, if you type in "television and violence not news" your search would be limited by excluding all web pages about violence on the evening news. For thorough searches you should consider all the possible synonyms or allied terms for your research topic: television, tv, cartoons, sitcoms, etc.

For another explanation using moving Venn diagrams see Internet 101. You might want to print out the following search strategy planner that will help you build an effective search about your research question.

To find out if a search engine has special options, always read the help section or the advanced search options. These options will help you limit or define your search even more, thus saving you time and producing more useful results.