This keyword is a built-in type. A variable of this type can have values true and false. Conditional expressions have the type bool and so have values of type bool. For example, i!=0 now has true or false depending on the value of i.
The values true and false have the following relationship:
!false == true !true == false
In the following statement:
if (condexpr1) statement1;
If condexpr1 is true, statement1 is always executed; if condexpr1 is false, statement1 is never executed.
When a postfix or prefix ++ operator is applied to a variable of type bool, the variable is set to true. The postfix or prefix -- operator cannot be applied to a variable of this type.
The bool type participates in integral promotions. An r-value of type bool can be converted to an r-value of type int, with false becoming zero and true becoming one. As a distinct type, bool participates in overload resolution.