Pointer to Pointer in C

C Pointer to Pointer

• In C pointer to pointer concept, a pointer refers to the address of another pointer.
• In c language, a pointer can point to the address of another pointer which points to the address of a value. Let's understand it by the diagram given below:

Pointer to Pointer

• Let's see the syntax of pointer to pointer.

int **p2;  

C pointer to pointer example

• Let's see an example where one pointer points to the address of another pointer.

• As you can see in the above figure, p2 contains the address of p (fff2) and p contains the address of number variable (fff4).

Changing Value Pointed by Pointers

Let's take an example.

int* pc, c;

c = 5;

pc = &c;

c = 1;

printf("%d", c);    // Output: 1

printf("%d", *pc);  // Ouptut: 1

• We have assigned the address of c to the pc pointer.
• Then, we changed the value of c to 1. Since pc and the address of c is the same, *pc gives us 1.

#include <stdio.h>        
#include <conio.h>      
void main(){        
int number=50;    
int *p;//pointer to int  
int **p2;//pointer to pointer      
clrscr();    
p=&number;//stores the address of number variable    
p2=&p;  
        
printf("Address of number variable is %x \n",&number);    
printf("Address of p variable is %x \n",p);    
printf("Value of *p variable is %d \n",*p);    
printf("Address of p2 variable is %x \n",p2);    
printf("Value of **p2 variable is %d \n",**p);    
    
getch();        
}

Expected Output:-

 Address of number variable is fff4

Address of p variable is fff4

Value of *p variable is 50

Address of p2 variable is fff2

Value of **p variable is 50