2.11: Boolean Data Type

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Overview

A Boolean data type has one of two possible values (usually denoted true and false), intended to represent the two truth values of logic and Boolean algebra. It is named after George Boole, who first defined an algebraic system of logic in the mid 19th century. The Boolean data type is primarily associated with conditional statements, which allow different actions by changing control flow depending on whether a programmer-specified Boolean condition evaluates to true or false.^[1]

Discussion

The Boolean data type is also known as the logical data type and represents the concepts of true and false. The name “Boolean” comes from the mathematician George Boole; who in 1854 published: An Investigation of the Laws of Thought. Boolean algebra is the area of mathematics that deals with the logical representation of true and false using the numbers 0 and 1. The importance of the Boolean data type within programming is that it is used to control programming structures (if then else, while loops, etc.) that allow us to implement “choice” into our algorithms.

The Boolean data type has the same attributes and acts or behaves similarly in all programming languages. However, while all languages recognize false as 0, some languages define true as -1 rather than 1. This is the result of storing the Boolean values as an integer and using a one’s complement representation that negates all bits rather than only the rightmost bit. To simplify processing, most programming languages recognize any non-zero value as being true.

Language	Reserved Word	True	False
C++	`bool`	`true`	`false`
C#	`bool` or `Boolean`	`true`	`false`
Java	`bool`	`true`	`false`
JavaScript	`Boolean()`	`true`	`false`
Python	`bool()`	`True`	`False`
Swift	`Bool`	`true`	`false`

Key Terms

Boolean: A data type representing the concepts of true or false.

one’s complement: The value obtained by inverting all the bits in the binary representation of a number (swapping 0s for 1s and vice versa).

References

cnx.org: Programming Fundamentals – A Modular Structured Approach using C++

Wikipedia: Boolean data type ↵