#include <stdio.h>

// pass a number to an array by reference, do math on it then return it

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

int main()
{
        int num = 0;
        printf("the address of int num is 0x%x\n", &num);
        add(&num);
        printf("num after add() is %d\n\n", num);

        printf("nexxxxxxxxxxxxxxxxxxxxxt\n");
        printf("------------------------\n");

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

        ptr = &num2;    // pointer now holds the address of num
        printf("num2 is %d\n", num2);
        printf("the pointer of num2 is 0x%x\n", ptr);

        num2 = 20;              // i is now 20
        printf("num2 is now %d\n", num2);
        *ptr = 22;
        printf("num2 (*p = 22) is now %d\n", num2);

        add(&num2);
        printf("num2 passed to add() is %d\n", num2);
}