C++ Pointers

Pointers are an important part of C++. They allow a program to work directly with memory addresses. Pointers may look confusing at first, but the basic idea is simple. A normal variable stores a value, while a pointer stores the address of another variable. Let’s start understanding C++ Pointers.

What is a Pointer?

Suppose we have:

int age = 14;

The variable age stores the value 14.

Every variable is stored somewhere in the computer’s memory. A pointer can store the memory address of that variable.

Think of it like this:

age     → 14
pointer → address of age

Creating a Pointer

A pointer is declared using *.

int* ptr;

Here, ptr is a pointer that can store the address of an int variable.

To store the address of a variable, use the & operator.

int age = 14;
int* ptr = &age;

Here:

• age stores 14.
• &age gets the address of age.
• ptr stores that address.

Getting the Address of a Variable

The & operator is called the address-of operator.

Example:

#include <iostream>
using namespace std;

int main() {
    int age = 14;

    cout << &age;

    return 0;
}

The output will be a memory address, which may look something like:

0x7ffca1234567

The exact address will be different each time the program runs.

Accessing a Value Using a Pointer

The * operator can also be used to get the value stored at the address held by a pointer.

This is called dereferencing.

#include <iostream>
using namespace std;

int main() {
    int age = 14;
    int* ptr = &age;

    cout << *ptr;

    return 0;
}

Output:

14

Here, ptr stores the address of age, and *ptr gives us the value stored at that address.

Changing a Value Using a Pointer

A pointer can also be used to change the value of a variable.

#include <iostream>
using namespace std;

int main() {
    int age = 14;
    int* ptr = &age;

    *ptr = 15;

    cout << age;

    return 0;
}

Output:

15

Changing *ptr changes the value of age because both refer to the same memory location.

Pointer Example

Let’s look at the address, pointer, and value together.

#include <iostream>
using namespace std;

int main() {
    int number = 25;
    int* ptr = &number;

    cout << "Value: " << number << "\n";
    cout << "Address: " << &number << "\n";
    cout << "Pointer: " << ptr << "\n";
    cout << "Value using pointer: " << *ptr;

    return 0;
}

The output will look similar to:

Value: 25
Address: 0x7ffca1234567
Pointer: 0x7ffca1234567
Value using pointer: 25

The exact memory address will be different on different systems and program runs.

Pointers and Arrays

Pointers are closely related to arrays.

For example:

#include <iostream>
using namespace std;

int main() {
    int numbers[3] = {10, 20, 30};

    int* ptr = numbers;

    cout << *ptr;

    return 0;
}

Output:

10

Here, ptr points to the first element of the array.

Pointers become especially useful when working with arrays, functions, and dynamic memory.

Null Pointer

A pointer that does not point to a valid object can be set to nullptr.

#include <iostream>
using namespace std;

int main() {
    int* ptr = nullptr;

    cout << "Pointer is not pointing to a value.";

    return 0;
}

nullptr is safer and clearer than leaving a pointer uninitialized.

A Simple Example

Let’s use a pointer to change a number.

#include <iostream>
using namespace std;

int main() {
    int number = 10;
    int* ptr = &number;

    cout << "Before: " << number << "\n";

    *ptr = 50;

    cout << "After: " << number;

    return 0;
}

Output:

Before: 10
After: 50

The pointer points to number, so changing *ptr changes the original variable.

Key Points to Remember

• A pointer stores the address of another variable.
• & gets the address of a variable.
• * is used to access the value at an address.
• Pointers can be used to change the original value.
• Pointers are closely related to arrays and memory management.
• nullptr represents a pointer that is not pointing to an object.

Mini Quiz

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C++ PROGRAMMING - QUIZ 11

1 / 5

Q1. What is a pointer in C++?

A variable that stores the address of another variable

A variable that stores only text

A function that changes values

A loop that repeats code

2 / 5

Q2. What does the & operator do when used with a variable?

It changes the variable's value

It gives the memory address of the variable

It deletes the variable

It creates a new pointer

3 / 5

Q3. What does dereferencing a pointer allow you to do?

Find the name of the pointer

Create a new variable

Access the value stored at the pointer's address

Stop the program

4 / 5

Q4. What can you do by changing the value through a pointer?

Change the original variable's value

Change the variable's data type

Delete the pointer

Create a new array

5 / 5

Q5. What does nullptr mean for a pointer?

The pointer contains a number

The pointer points to the first array element

The pointer is pointing to a valid value

The pointer is not pointing to a valid object

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#include <iostream>
using namespace std;

int main() {

    int number = 10;

    int* ptr = &number;

    cout << "Before: " << number << "\n";

    *ptr = 50;

    cout << "After: " << number;

    return 0;
}

What’s Next?

In the next chapter, we will learn about C++ Structures and see another simple way to create an alias for an existing variable.

Frequently Asked Questions (FAQs)

Written by Shubhranshu Shekhar, who has trained 20000+ students in coding.

Nidhi Srivastav