c语言---const搭配指针问题

如果const在'*'左边，则表示指针指向的变量的值不可变;   保存的值不变。

如果const在'*'右边，则表示指针的值是不可变的;  即是地址不变。

void test()

{
int a = 10;
int b = 20;

int * const p1 = &a;
printf("p1=%d\n",*p1); //10

//int * const p1; p1 read only
//p1 = &a;

//p1 = &b; error 

a = 100;
printf("p1=%d\n",*p1); //100

*p1 = 1000;
printf("p1=%d\n",*p1); //1000

int const *p2;
p2 = &b;
printf("p2=%d\n",*p2); //20

b = 200;
printf("p2=%d\n",*p2); //200

p2 = &a;
printf("p2=%d\n",*p2); //1000

//*p2 = 30; error

}