What is true and what is false?

In C, the concepts of true and false are represented using integers. The integer value 0 is considered false, and any non-zero value is considered true. However, C99 introduced the <stdbool.h> header, which defines the _Bool type and introduces the bool type and the constants true and false. Here are examples using both approaches:

Using integers:

#include <stdio.h>

int main() {
    // Using integers
    int trueValue = 1;
    int falseValue = 0;

    if (trueValue) {
        printf("This statement is true\n");
    } else {
        printf("This statement is false\n");
    }

    if (falseValue) {
        printf("This statement is true\n");
    } else {
        printf("This statement is false\n");
    }

    return 0;
}

In this example, the conditions inside the if statements are evaluated based on the truthiness or falsiness of the integer values.

Using <stdbool.h>:

#include <stdio.h>
#include <stdbool.h>

int main() {
    // Using <stdbool.h>
    bool trueValue = true;
    bool falseValue = false;

    if (trueValue) {
        printf("This statement is true\n");
    } else {
        printf("This statement is false\n");
    }

    if (falseValue) {
        printf("This statement is true\n");
    } else {
        printf("This statement is false\n");
    }

    return 0;
}

Here, the <stdbool.h> header is included, and the bool type is used with true and false constants. This makes the code more readable and expressive.

Both examples will produce the same output:

This statement is true
This statement is false

In C, it's common to see the integer approach, especially in older codebases. However, using bool from <stdbool.h> provides better readability and is preferred in modern C programming.

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Written by

Jyotiprakash Mishra
Jyotiprakash Mishra

I am Jyotiprakash, a deeply driven computer systems engineer, software developer, teacher, and philosopher. With a decade of professional experience, I have contributed to various cutting-edge software products in network security, mobile apps, and healthcare software at renowned companies like Oracle, Yahoo, and Epic. My academic journey has taken me to prestigious institutions such as the University of Wisconsin-Madison and BITS Pilani in India, where I consistently ranked among the top of my class. At my core, I am a computer enthusiast with a profound interest in understanding the intricacies of computer programming. My skills are not limited to application programming in Java; I have also delved deeply into computer hardware, learning about various architectures, low-level assembly programming, Linux kernel implementation, and writing device drivers. The contributions of Linus Torvalds, Ken Thompson, and Dennis Ritchie—who revolutionized the computer industry—inspire me. I believe that real contributions to computer science are made by mastering all levels of abstraction and understanding systems inside out. In addition to my professional pursuits, I am passionate about teaching and sharing knowledge. I have spent two years as a teaching assistant at UW Madison, where I taught complex concepts in operating systems, computer graphics, and data structures to both graduate and undergraduate students. Currently, I am an assistant professor at KIIT, Bhubaneswar, where I continue to teach computer science to undergraduate and graduate students. I am also working on writing a few free books on systems programming, as I believe in freely sharing knowledge to empower others.