C++ LANGUAGE POINTER TO POINTER

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C++ LANGUAGE POINTER TO POINTER

Pointer to a Pointer 


A pointer to a pointer is a form of multiple indirection 
or a chain of pointers. Normally, a pointer contains the 
address of a variable. When we define a pointer to a pointer, 
the first pointer contains the address of the second pointer, 
which points to the location that contains the actual value 
as shown below. 
 
A variable that is a pointer to a pointer must be declared 
as such. This is done by placing an additional asterisk in 
front of its name. For example, following is the declaration 
to declare a pointer to a pointer of type int: 

int **var; 

When a target value is indirectly pointed to by a pointer to 
a pointer, accessing that value requires that the asterisk 
operator be applied twice, as is shown below in the example: 

#include <iostream> 
  
using namespace std; 
  
int main () 
{ 
   int  var; 
   int  *ptr; 
   int  **pptr; 
 
   var = 3000; 
 
   // take the address of var 
   ptr = &var; 
 
   // take the address of ptr using address of operator & 
   pptr = &ptr; 
 
   // take the value using pptr 
   cout << "Value of var :" << var << endl; 
   cout << "Value available at *ptr :" << *ptr << endl; 
   cout << "Value available at **pptr :" << **pptr << endl; 
 
   return 0; 
} 
When the above code is compiled and executed, 
it produces the following result: 

Value of var :3000 
Value available at *ptr :3000 
Value available at **pptr :3000