对指针的理解

int main(void)

{

　　int a;

　　int *p;

　　int **p1;

　　a = 5;

　　p = &a;

　　p1 = &p;

 

　　printf("\n");

　　printf("the address of a is %p\n", &a);

　　printf("the value of p is %p and the adress of p is %p\n", p, &p);

　　printf("the value of p1 is %p and the address of p1 is %p\n",p1, &p1);

 

　　printf("\n\n");

 

　　printf("a's value is %d\n", a);

　　printf("a's value is %d access by first pointer\n", *p);

　　printf("a's value is %d access by second pointer\n",*(*p1));

 

　　printf("\n");

}

输出结果如下：

the address of a is 0x7fffd57a181c

the value of p is 0x7fffd57a181c and the adress of p is 0x7fffd57a1808

the value of p1 is 0x7fffd57a1808 and the address of p1 is 0x7fffd57a1810

 

 

a's value is 5

a's value is 5 access by first pointer

a's value is 5 access by second pointer

解析：
p = &a;
p = 变量 a的地址 = 0x7fffd57a181c
*p = a的值 = 5  //一级指针

p1 = &p;
p1 = 变量p的地址
*p1 = 变量p的值=a变量的地址
*(*p1) = *(变量p的值)=*(变量a的地址)=5