pointer to pointer

#include <stdio.h>
#include <stdlib.h>

void f1(int *v)
{
    printf("f1: %d\n", *v);
}

void f2(int *v1, int **v2)
{
    *v2 = v1;
}


int main()
{

    int a = 123;
    int b = 789;
    int *p;

    p=&a;

    printf("a: %d\n", a);
    printf("b: %d\n", b);

    f1(p);

    printf("*p: %d\n", *p);

    f2(&b, &p);

    printf("*p: %d\n", *p);

    return 0;
}

/*
output:

a: 123
b: 789
f1: 123
*p: 123
*p: 789

*/