Dereferencing Pointers in C/C++

A pointer is a variable, which stores a memory address. This memory can be from stack, or from heap.

In this lecture, we’ll explain how to initialise a pointer in C++, using the address operator i.e. & operator. Then we will also discuss how to access the data in the memory through a pointer, which contains the address of that memory location. For this we will use the Dereference Operator i.e. * operator.

Using Address Operator (&) to Initialize a Pointer

the symbol &, represents the address operator. It is a unary operator, and when applied on a variable, then it returns the memory address of that variable.

When you declare a variable in C++, the system reserves a memory space in stack for that variable, and by applying the & operator before that variable, we can get address of that memory space. Then we can store that memory address into a pointer.

For example,

#include <iostream>

int main() 
{
    // Create a Variable
    int num = 77;

    // Initialize a Pointer with the 
    // memory address of variable num
    int* ptr = &num;

    std::cout << "Address of num: " << ptr << std::endl;

    return 0;
}

Output:

Address of num: 0x7ffe17223d8c

This will print the memory address where num is stored. The output could be something like: 0x7ffe17223d8c.

Using Dereference Operator (*) to Access Data in Memory

Suppose we have a pointer, that points to a memory location. Now we want to access the data at that memory location. We can do that, by applying a dereference operator(*) on that pointer.

#include <iostream>

int main() 
{
    // Create a Variable
    int num = 77;

    // Initialize a Pointer with the 
    // memory address of variable num
    int* ptr = &num;

    std::cout << "Value at Memory Address: " << *ptr << std::endl;

    return 0;
}

Output:

Value at Memory Address: 77

This will print the value of num by using the pointer ptr. The output will be: 77.

The dereference operator, denoted by *, is used to access the value stored at the memory location pointed to by a pointer.

Difference b/w Address Operator (&) and Dereference Operator (*)

Although both the & and * operators are related to pointers, but still they are very much different. The main difference is as follows:

• The Address Operator (&), is used to get the memory address of a variable. Whereas, the Dereference Operator (*) is used to access the value of the variable located at the address specified by the pointer.

Summary

Pointers helps a developer in managing and manipulating data in C++. We learned how to initialize a pointer using Address Operator and how to access the value value of the variable located at the address specified by the pointer, using a Dereference Operator.