C++ Pointer to Pointer (Multiple Indirection)

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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:

Example

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:

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, Output Will Be :

Example

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


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