C++ Pointers Pointers

Syntax

A Pointer Pointer in C++ is a pointer to another pointer or a double pointer. The syntax for declaring a pointer pointer is as follows:

datatype** var_name;

Example

Here's an example of a pointer pointing to another pointer:

int main() {
    int a = 5;
    int* ptr1 = &a;
    int** ptr2 = &ptr1;

    cout << "The value of a: " << a << endl;
    cout << "The value of ptr1: " << *ptr1 << endl;
    cout << "The value of ptr2: " << **ptr2 << endl;

    return 0;
}

Output

The output of the above code will be:

The value of a: 5
The value of ptr1: 5
The value of ptr2: 5

Explanation

In the above code, we first declare an integer variable a and initialize it to 5.

Then, we declare a pointer ptr1 and assign it the address of a. This means that ptr1 is now pointing to a.

Next, we declare a pointer pointer ptr2 and assign it the address of ptr1. This means that ptr2 is now pointing to ptr1.

We then print the value of a, which is 5, by dereferencing a using the * operator on ptr1.

Similarly, we print the value of ptr1 by dereferencing ptr1 using the * operator on ptr2.

Finally, we print the value of a again by dereferencing a twice using the ** operator on ptr2.

Use

Pointer pointers are often used in advanced data structures such as trees and graphs.

They can also be used to create dynamic arrays of pointers.

Important Points

• A pointer pointer is a pointer to another pointer.
• The syntax for declaring a pointer pointer is datatype** var_name;.
• We can access the value of a pointer pointer by using the ** operator.
• Pointer pointers are often used in advanced data structures.

Summary

In this tutorial, we learned about pointer pointers in C++. We saw how to declare a pointer pointer, how to access its value, and where it is commonly used. We also saw an example and the output of a program that uses a pointer pointer.