Pointer to pointer in C programming language

The concept of pointer can be extended further. Pointer can hold the address of another variable. But what will happen if the variable itself is a pointer. The address of a pointer can be stored on a variable which is called pointer to pointer.

#include< stdio.h >

void main()

{

 int i,*j,**k;

 /* here j is a pointer and k is pointer to pointer*/

 i=5;

 j=&i;

 k=&j;

  printf("\nAddress of 'i'=%u",&i);

  printf("\nAddress of 'i'(displayed through 'j')=%u",j);

  printf("\nAddress of 'i'(displayed through 'k')=%u",*k);

  printf("\nAddress of 'j'=%u",&j);

  printf("\nAddress of 'j'(displayed through 'k')=%u",k);

  printf("\nAddress of 'k'=%u",&k);

  printf("\nNow the values...\n");

  printf("\nValue of 'j'( this will be the address of 'i')=%u",j);

  printf("\nValue of 'k' (this will be the address of 'j')=%u",k);

  printf("\nValue of 'i' displayed through 'j'=%d",*j);

  printf("\nValue of 'i' displayed through 'k'=%d",**k);

 }

A chart will demonstrate this feature

Location

 Name       i          j          k

Value      5       1002     1000       

Address 1002  1000      998

Difference between *ptr++ and ++*ptr  (assume ptr is a pointer and pointing to some location)

*ptr++ statement increments the pointer means the pointer moves to the next location while ++*ptr statement increments the value of the location pointed by the pointer by 1.

++*ptr statement can be also written as (*ptr)++

Another example using C Language

#include< stdio.h >

void main()

{

 int x,*y;

 void *z;

 x=10;

 z=&x;

 y=(int *)z;

printf("\nAddress of 'x'=%u",&x);

printf("\nAddress of 'x'through 'y'=%u",y);

printf("\nAddress of 'x' through 'z'=%u",z);

}

 all the three statements will generate the same output, address of the variable ‘x’