14、 C pointer explanation (IV): pointer of pointer

One 、 The pointer of the pointer

Pointer is used to store the address of the variable , meanwhile , The pointer also has its own address , therefore , You can set a pointer variable , The address used to store the pointer , That's the pointer of the pointer , What he keeps is an address , Pass value character * You can take out the value of the corresponding position

• Format ：**p

• Picture explanation ：
  

• Code implementation ：

  #include<stdio.h>
  
  int main(){
        
      int a = 10;
      int *p1;
      int **p2;
      int ***p3;
      p1 = &a;
      p2 = &p1;
      p3 = &p2;
      printf("a Value ：%d\n",a);
      printf("p1 The value of the address （a The address of ）：%p\n",p1);
      printf("p1 The value of the address store （a Value ）：%d\n",*p1);
      printf("p2 The value of the address （p1 The address of ）：%p\n",p2);
      printf("p2 The value of the address store （p1 Value ,a The address of ）：%p\n",*p2);
      printf("p2 The value of the integer stored in the address （a Value ）：%d\n",**p2);
      printf("p3 The value of the address （p2 The address of ）：%p\n",p3);
      printf("p3 The value of the address store （p2 Value ,p1 The address of ）：%p\n",*p3);
      printf("p3 The value of the integer stored in the address （a Value ）：%d\n",***p3);
      return 0;
  }
  

• Running results ：

  a Value ：10
  p1 The value of the address （a The address of ）：0x7ffd25ad858c
  p1 The value of the address store （a Value ）：10
  p2 The value of the address （p1 The address of ）：0x7ffd25ad8590
  p2 The value of the address store （p1 Value ,a The address of ）：0x7ffd25ad858c
  p2 The value of the integer stored in the address （a Value ）：10
  p3 The value of the address （p2 The address of ）：0x7ffd25ad8598
  p3 The value of the address store （p2 Value ,p1 The address of ）：0x7ffd25ad8590
  p3 The value of the integer stored in the address （a Value ）：10