This was first created by an English mathematician named George Boole in 1847 and yet, in one of the strange quirks of the computer industry, is now used in everything from circuit design to searching the Internet. In essence Boole developed a system for reducing complex questions into simple yes or no answers by using what are known as truth tables, sometimes called gates.
Although these truth tables or gates can take several forms the three that are relevant to Internet searches are AND, OR and NOT. Each one operates differently.
and
This produces an output only if two specified conditions are met. For example if a search was made on the words ‘Economic’ AND ‘Policy’ the truth table would be as follows:
1st Condition 2nd Condition Output
(Economic) (Policy)
NO NO NO
YES NO NO
NO YES NO
YES YES YES
Only if both words were found on the same website would a match be returned.
or
This produces an output if either specified condition is met. In the same example as above the truth table would be:
1st Condition 2nd Condition Output
(Economic) (Policy)
NO NO NO
YES NO YES
NO YES YES
YES YES YES
If either word is found on a website a match would be returned.
not
This returns an output only if a specified condition is not met. To continue the above example if a search was made on the words ‘Economic’ NOT ‘Policy’ the truth table would be:
1st Condition 2nd Condition Output
(Economic) (Policy)
YES YES NO
NO YES NO
YES NO YES
NO NO NO
Only websites which contain the word ‘Economic’ but do not contain the word ‘Policy’ will be returned.
In electronics the output from one set of gates can become the input to others to produce complex switching arrangements which forms the basis of the computer microchip itself. Away from that it is by combining these various logical operators (as AND, OR and NOT are known) that highly precise Internet searches can be conducted, as will soon become clear.
Dinesh Thakur holds an B.C.A, MCDBA, MCSD certifications. Dinesh authors the hugely popular