# 指向指针的指针

指针可以指向一份普通类型的数据，例如 int、double、char 等，也可以指向一份指针类型的数据，例如 int *、double *、char * 等。如果一个指针指向的是另外一个指针，我们就称它为二级指针，或者指向指针的指针。

指针变量也是一种变量，也会占用存储空间，也可以使用`&`获取它的地址。C语言不限制指针的级数，每增加一级指针，在定义指针变量时就得增加一个星号`*`。p1 是一级指针，指向普通类型的数据，定义时有一个`*`；p2 是二级指针，指向一级指针 p1，定义时有两个`*`。

实际开发中会经常使用一级指针和二级指针，几乎用不到高级指针。

想要获取指针指向的数据时，一级指针加一个`*`，二级指针加两个`*`，三级指针加三个`*`，以此类推，请看代码：

```c
#include <stdio.h>
int main(){
    int a =100;
    int *p1 = &a;
    int **p2 = &p1;
    int ***p3 = &p2;
    printf("%d, %d, %d, %d\n", a, *p1, **p2, ***p3);
    printf("&p2 = %#X, p3 = %#X\n", &p2, p3);
    printf("&p1 = %#X, p2 = %#X, *p3 = %#X\n", &p1, p2, *p3);
    printf(" &a = %#X, p1 = %#X, *p2 = %#X, **p3 = %#X\n", &a, p1, *p2, **p3);
    return 0;
}
```


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