Demonstraing passing by reference in C.

incr.c

#include <stdio.h>

void incr(int *x){
    *x += 1;
}

int main(){
    // initialize i to be equal to 6
    int i = 6;
    printf("i = %d\n", i);
    // increment it by passing it's value by reference
    incr(&i);
    printf("i = %d\n", i);

    return 0;
}