hts.StevenWood.com

Boolean expressions

Boolean expression can have only two possible values,
true or false.

A Boolean expression may be a single Boolean variable or consist of a comparison. A simple comparison comparison has the form:

expression    comparison operator    expression

The comparison operators are:

You can indicate the opposite by using the exclamation mark (!) in front of the boolean value. The ! mean "not". e.g. if you have two boolean variables x and y and

x = true; then
y= !x; means that y = false ( "not" true);

Boolean variables, or comparisons can be combined using the boolean or logical operators && for and, and || for or. If two boolean expressions are combined using the operator && then both must be true before the compound expression is true. If they are combined using the || operator then at least one of the two must be true before the compound expression is true. The Boolean logic is shown here.

Here is a Boolean expression which will test whether an exam mark submitted is a number between 0 and 100:

( 0 <= mark ) &&  ( mark <= 100 )

The value is true if mark is in this range.