eolas/zk/Booleans_in_C.md

tags
C

Booleans are a bit weird in C. Oficially they don't exist as a core primitive data type. Instead you use integers on the basis that:

0 is false and any non-zero value is true (but typically indicated with 1)

Hence why the int main() entrypoint returns int, because "success" is 1 and "error" is 0.

A common example of this approach:

int is_running = 1; // true
int has_error = 0; // false

if (is_running) {
    // Do stuff
}

Since the C99 standard, a dedicated Boolean type has been available.

#include <stdbool.h>

bool is_running = true;
bool has_error = false;

if (is_running) {
     // Do stuff
}

Note, you must include the bool header file which is part of the core in order to have access to the bool, true, and false keywords.

This is just syntactic sugar though, and underneath it is just int values for 0 and 1.