#include <stdio.h>

int * pGlobal;

void foo(void)
{
    *pGlobal = 900;
}

int main(void)
{
    int num = 15;

    pGlobal = &num;

    printf("\n%d", *pGlobal);
    printf("\n%d", num);

    *pGlobal = 5;

    printf("\n%d", *pGlobal);
    printf("\n%d", num);

    foo();

    printf("\n%d", *pGlobal);
    printf("\n%d", num);

    return 0;
}