對指針的理解，指針理解

對指針的理解，指針理解

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"); }
輸出結果如下：
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 = 變量 a的地址 = 0x7fffd57a181c
*p = a的值 = 5  //一級指針

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