Pass a pointer to an integer

In this example we pass a pointer to a function so inside the function we'll be able to change the content of the variable in the caller.

#include<stdio.h>

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


int main() {
    int counter = 0;

    printf("Counter: %d\n", counter);

    increment(&counter);
    printf("Counter: %d\n", counter);

    increment(&counter);
    printf("Counter: %d\n", counter);

    return 0;
}

Counter: 0
Counter: 1
Counter: 2