UMBC CS 201, Spring 06

UMBC CMSC 201
Spring '06
CSEE | 201 | 201 S'06 | lectures | news | help

Booleans, Relational and Logical Operators

C does NOT have a Bool data type

but the ideas of TRUE and FALSE are necessary in any language.

In C, 0 is false, and anything other than 0 is true.

Variables that will only contain "true" or "false" are called Boolean variables and are sometimes called "flags" (ugh!)

Boolean operators

Operators on boolean values consist of:

relational operators: >, <, >=, <=, ==, !=
logical operators: !, &&, ||

Truth Tables for AND, OR and NOT

We define boolean operators by truth tables which give the desired output for every possible combination of inputs.

Truth table - (P and Q)
P	Q	P && Q
FALSE	FALSE	FALSE
FALSE	TRUE	FALSE
TRUE	FALSE	FALSE
TRUE	TRUE	TRUE

Truth table - (P or Q)

p Q P || Q

FALSE FALSE FALSE

FALSE TRUE TRUE

TRUE FALSE TRUE

TRUE TRUE TRUE

Truth table -
not P

P ! P

FALSE TRUE

TRUE FALSE

CSEE | 201 | 201 S'06 | lectures | news | help

Monday, 23-Jan-2006 09:13:30 EST