A Boolean expression is a symbolic expression in a programming language that returns a value of either TRUE or FALSE (1 or 0). It generally includes variables grouped (as appropriate) by parentheses and separated from each other by operators such as AND, OR, NOT, <, and >. For example, the expression "p < q" is a Boolean expression because the state of affairs it expresses must, for definite values of p and q, be either TRUE or FALSE. If, for example, p = 2 and q = 5, then the value of "p < q" is TRUE. The expression "A AND B" is another Boolean expression. This statement is meaningful only if A and B are each restricted to the two possible values of TRUE and FALSE; if either A or B is false, the expression "A AND B" has the value FALSE.

Boolean expressions employ Boolean algebra, a two-valued system of algebra that represents logical...