#include <stdio.h>
void add(int *x)
{
        *x = *x + 1;
}

int main()
{
        int num = 0;
        add(&num);

        int num2 = 15;
        int *ptr;       // integer pointer - points to an int, stores a memory address

        ptr = &num2;    // pointer now holds the address of num

        num2 = 20;              // i is now 20

        *ptr = 22;

        add(&num2);
}