Demystifying C++ Booleans: Data Types and Logic Operators Guide - w9school

Unlock the potential of C++ Booleans! Dive into data logic, grasp Boolean types, and elevate your coding with essential logical operators. Explore true and false in C++ for robust, efficient programming.

Demystifying C++ Booleans: Data Types and Logic Operators Guide - w9school

C++ Booleans

Booleans form the cornerstone of many programming language control structures, from if/else to loops. Utilizing appropriate types for boolean inputs helps maintain clean code that clearly communicates your intentions to callers.

Boolean values only offer two states: true or false. Although Booleans seem limited in scope, there are several predefined values which can be assigned to a variable of this data type (referred to as an enumerator or element). Examples may include genre such as rock and jazz music as well as specific items on shopping lists such as bananas or peanut butter.

C programming language defines Boolean values with the bool type. You can create variables directly using std::cin functions, but for greater expression use bool as the return type for one of your functions - it will allow you to communicate more precisely your intentions than an int.

There are three boolean operators you can use to combine or evaluate boolean expressions: the AND (and), OR (or), and NOT (not).

By performing explicit or implicit type conversion, it's also possible to convert non-bool values to bools. Zero is considered false while any non-zero integer or floating point number can be converted using constructs like bool(value) or value!= 0. However, precision constraints do apply so be mindful when making conversions such as this as precision restrictions apply. Furthermore, bools provide memory efficiency as they store only 1 of 2 different values without taking up space with extraneous data.

Often, when programming, you'll require a data type that may be limited to two options, for example:

  • YES / NO
  • ON / OFF

To do this, C++ has an boll data type that can accept either false (1) as well as false (0).

Boolean Values

A boolean value is identified by the word bool keyword. It can only be used to determine the values either true either true or:


bool isCodingFun = true;
bool isFishTasty = false;
cout << isCodingFun;  // Outputs 1 (true)
cout << isFishTasty;  // Outputs 0 (false)

In the above example you can see that the real value will return 1 True returns 1, while the false value returns zero.

It is however more typical to return a boolean number through comparison of the values with variables (See Below).

C++ Boolean Expressions

Boolean Expression

A Boolean function yields a boolean value that is one of either (true) as well as zero (false).

This helps to develop the ability to think and come up with answers.

You can employ an comparison Operator for example, like greater than ( >) operator greater than ( >) operator, to figure whether an phrase (or variables) can be said to be true or not:


int x = 10;
int y = 9;
cout << (x > y); // returns 1 (true), because 10 is higher than 9

Perhaps even more simple:


cout << (10 > 9); // returns 1 (true), because 10 is higher than 9

In the following examples we will use in the examples below, we use equal ( ==) operator to assess an expression like:


int x = 10;
cout << (x == 10);  // returns 1 (true), because the value of x is equal to 10


cout << (10 == 15);  // returns 0 (false), because 10 is not equal to 15

Real-life Example

Let's imagine a "real-life example" where we must determine the age of a person to be able to vote.

In the following example, we will use an = compare operator in order to figure out whether you are ( 25) is more than or equivalent to the age limit for voting that is set to 18, which is:


int myAge = 25;
int votingAge = 18;

cout << (myAge >= votingAge); // returns 1 (true), meaning 25 year olds are allowed to vote!

Cool, right? Another option (since we're having a blast right now) is to wrap the code above into the form of an if...else statement, in order to take different actions based on the results:


Output "Old enough to vote!" If your age is higher that or less than 18.. If not, output "Not old enough to vote. ":

int myAge = 25;
int votingAge = 18;

if (myAge >= votingAge) {
  cout << "Old enough to vote!";
} else {
  cout << "Not old enough to vote.";

// Outputs: Old enough to vote!

Booleans are the foundation for every C++ comparison and condition.

The details about the conditions ( if...else) in the coming blog.

How to Avoid Mistakes When Using Booleans in C++

  • Booleans can be an invaluable addition to your code and can make things run more quickly. However, improper use may result in errors. So in this article we'll offer some helpful hints for using booleans correctly and avoiding mistakes when doing so.

  • Modern C++ offers a Boolean data type that can accept either true or false values, making them useful for checking conditions in loops and if/else statements; however, newcomers to the language may find them confusing.

  • C++ differs from other programming languages by not providing an inherent Boolean data type; therefore, Booleans must be manually declared and assigned using either keywords such as bool and boolean_true or logic operators such as AND, OR, XOR, or NOT to declare and assign their values.

  • C++ makes an unusual distinction when it comes to evaluating booleans: instead of being evaluated simultaneously with other integer values, they're short-circuited at the time of evaluating an AND or OR operator; specifically, if one expression evaluates to a boolean value of one and another expression on the right-hand side evaluates to a boolean variable of one, then both will always be evaluated as being equivalent - something new programmers are often caught out by. This common miscalculation often catches newcomers by surprise!

  • Beginning programmers often find booleans to be rather confusing, as their behavior differs significantly from a number. However, this can actually help create greater clarity of intent, as a boolean value indicates whether a function returns something either true or false and not simply numbers.

  • Newcomers often struggle with inputting Boolean variables using std::cin, as it only accepts inputs that are either true or false. When trying to enter non-boolean values, it will simply fail and print "0" at that line in your program.

  • To avoid this scenario, new programmers are advised to compile their code using the boolalpha flag. This will cause std::cin to treat all inputs as booleans instead of failing when receiving non-boolean values.

  • There are other features that aid clarity of intent when working with booleans in your code, too. While using the boolalpha flag may cause bugs and unexpected behavior on certain CPU architectures, it should only be used when needed, for instance, to detect exceptional conditions like failed resource allocation or severe input failures as exceptions. Otherwise, it would be more appropriate to return an integer for functions' return values; this will make the language less confusing for newcomers while still taking advantage of other features like function overloading.

C++ Exercises

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