# Booleans — primitive type

George Boole developed the true/false system logic in the 19^{th} century. Consequently, the word *Boolean* is derived from his name.

In JavaScript, Boolean logic allows your program to make decisions. A Boolean logic statement consists of a condition that evaluates to either *true* or *false*. You can think of the condition as a question that has one of two possible answers:

- yes or no,
- ON or OFF, or
- positive or negative
- true or false

When working with Boolean logic, keep in mind there is no "maybe" or third possibility. Thus a Boolean type a can be used anytime there is only one possible outcome out of two possible outcomes.

A Boolean type is useful in situations where you want the program to act according to the value it represents. For instance, let's say our program has to determine whether a person is at least 18 years of age to apply for a driving license. In the program, we would ask the applicant's date of birth and then we would calculate applicant's age. Then we would ask the following questions programmatically: is this applicant's age at least 18 years of age. The answer to this question would be either yes or no. In this case, we could use a Boolean type to store our response. If our response is *yes* to our question, then, the applicant does meet the minimum age requirement for the license. If, however, our response if *no*, then the applicant does not meet the minimum age requirement. The following summarizes our Boolean logic example: