二级指针修改一级指针的值

#include <stdio.h>#include <stdlib.h>#include<process.h>#include<windows.h>int a=10,b=20;change(int *p){    p=&b;}changepp(int **pp){    *pp=&b;}int main(){    int *p=&a;    change(p);    printf("%d\n",*p);    changepp(&p);    printf("%d\n",*p);    return 0;}