Changing address contained by pointer using function

Question

If I\'ve declared a pointer p as int *p; in main module, I can change the address contained by p by assigning p=&a; w

Answer 1

In C, variables are passed by value - a copy of the pointer is passed to the function. Use another pointer to the pointer instead:

void change(int **p, int *someOtherAddress)
{
    *p = someOtherAddress;
}

int a = 1, b = 2;
int *p = &a;

printf("*p = %d\n", *p);
change(&p, &b);
printf("*p = %d\n", *p);

This prints

*p = 1
*p = 2