✅ <stdbool.h> — Boolean Type (C99+)

Adds the bool type and true/false constants to C. Available since C99.

Include: #include <stdbool.h> | Compile: gcc -Wall -o prog prog.c

📋 Functions & Macros

Name	Prototype / Value	Description
bool	typedef _Bool bool	Boolean type (0 or 1)
true	#define true 1	Boolean true constant
false	#define false 0	Boolean false constant

💡 Example Program

Copy, save as demo.c, and compile with the command shown at the bottom.

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

bool is_even(int n)  { return (n % 2 == 0); }
bool is_prime(int n) {
    if (n < 2) return false;
    for (int i = 2; i * i <= n; i++)
        if (n % i == 0) return false;
    return true;
}

int main(void) {
    for (int i = 1; i <= 20; i++) {
        printf("%2d: even=%-5s prime=%s\n",
               i,
               is_even(i)  ? "true" : "false",
               is_prime(i) ? "true" : "false");
    }
    return 0;
}
/* Compile: gcc -Wall -std=c99 -o bool_demo bool_demo.c */

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