Boolean Logic: Boolean Logic

Boolean Logic is Algebra that works with logical rather than numeric relationships.

• Boolean algebra was introduced in 1854 by George Boole
• Boole devised a mathematical language to deal with questions of logic.
• Boole is now considered the father of modern information technology

Algebra comes from the Arabic al-jebr meaning "reunion of broken parts" (jebr can be pronounced either gobre or jobre)

• Algebra uses letters to represent unknown numbers
• In Algebra variables like x and y = numerical values
  • for example x + 4 = 8

Boolean Logic is a form of algebra in which the variables have a logical value of TRUE or FALSE.

• In Boolean algebra x and y = classes of objects
  • for example x = triangles and y = circles   

Boolean Operators

AND = Can be thought of as BOTH.  It requires that both or all objects (search terms) be present in the results.  In online searching AND serves to narrow the search and is used for combining differing concepts.

OR = Can be thought of as EITHER.  It is used to find either one term or another.  In online searching OR serves to broaden a search and is used to search synonymous or closely related terms.

NOT = Can be thought of as AND NOT.  It is used to eliminate records.  In online searching it serves to narrow a search.  Exercise caution when using the Boolean NOT as needed concepts may be eliminated unintentionally.