Address and dereference operators in C++

Introduction

We use address and dereference operators to work with memory locations directly. This helps us access or change the value stored in a specific place in the computer's memory.

When you want to find the memory address of a variable.

When you want to access or change the value stored at a specific memory address.

When working with pointers to manage dynamic memory.

When passing large data to functions efficiently by using pointers.

When implementing data structures like linked lists or trees.

Syntax

C++

int* ptr = &variable;  // & is address operator
int value = *ptr;        // * is dereference operator

The & operator gives the memory address of a variable.

The * operator accesses the value stored at the memory address a pointer holds.

Examples

Here, p points to x. Using *p gets the value of x.

C++

int x = 10;
int* p = &x;  // p stores address of x
int y = *p;   // y gets value 10 from address stored in p

Dereferencing ptr lets us change a through the pointer.

C++

int a = 5;
int* ptr = &a;
*ptr = 20;  // changes value of a to 20

Prints the memory address of num and its value using pointer.

C++

int num = 7;
int* pNum = #
std::cout << "Address: " << pNum << " Value: " << *pNum << std::endl;

Sample Program

This program shows how to get the address of a variable, access its value through a pointer, and change the value using the dereference operator.

C++

#include <iostream>

int main() {
    int value = 42;
    int* pointer = &value;  // store address of value

    std::cout << "Value: " << value << "\n";
    std::cout << "Address of value: " << pointer << "\n";
    std::cout << "Value via pointer: " << *pointer << "\n";

    *pointer = 100;  // change value using pointer
    std::cout << "New value: " << value << "\n";

    return 0;
}

Important Notes

Memory addresses shown when running may look different each time.

Always initialize pointers before dereferencing to avoid errors.

Using * on a pointer accesses or changes the value at that memory location.

Summary

The & operator gets the address of a variable.

The * operator accesses or changes the value at the address a pointer holds.

Pointers let you work directly with memory, which is useful for efficient programming.