CPP Tutorials

Explore the ‘delete’ Operator in CPP


Welcome to the world of C++ programming, where we’re about to unravel the secrets of the “delete” keyword! In this article, we’re going to dive into all the important aspects: why we need it, what it actually is, and how we can use it to our advantage. Just like when we create something with the “new” operator, sometimes we need to clean up after ourselves in the world of programming. The “delete” keyword is like a magic spell that helps us properly remove things we’ve created, ensuring our programs stay efficient and tidy. So, let’s embark on this journey and master the art of using the “delete” keyword in C++!

What is the ‘delete’ Operator in C++?

In C++, the ‘delete’ operator is a crucial tool used to manage memory allocated dynamically during program execution. When we create variables or objects dynamically using keywords like ‘new’, the memory space they occupy is allocated on the heap. It’s the programmer’s responsibility to free up this memory once it’s no longer needed to prevent memory leaks.

The ‘delete’ operator is used to deallocate memory that was previously allocated using the ‘new’ operator. It returns the memory back to the system’s memory pool, making it available for other parts of the program or other processes to use. Failing to ‘delete’ dynamically allocated memory can result in memory leaks, where memory is not properly released, leading to inefficient memory usage and performance problems over time.

Here’s the syntax for using the ‘delete’ operator:

delete pointer;

In this syntax, ‘pointer’ is a pointer variable pointing to the dynamically allocated memory that you want to deallocate.

Let’s look at a simple code example to understand its usage:

using namespace std;

int main() {
    int* ptr = new int;  // Allocating memory on the heap
    *ptr = 10;  // Assigning a value

    cout << "Value before delete: " << *ptr << endl;

    delete ptr;  // Deallocating memory

    // Attempting to access the memory after deletion can result in undefined behavior
    // cout << "Value after delete: " << *ptr << endl; 

    return 0;


Value before delete: 10


  • Memory Allocation: The code allocates memory on the heap for an integer using the ‘new’ operator.
  • Value Assignment: A value of 10 is assigned to the dynamically allocated memory using the pointer.
  • Memory Deallocation: The ‘delete’ operator is used to free the allocated memory after it’s no longer needed.
  • Avoid After Deletion: Trying to access the memory after using ‘delete’ can result in unpredictable behavior, as the memory is no longer valid.
  • Proper Memory Management: Using ‘delete’ is crucial for preventing memory leaks and ensuring efficient memory usage in programs. Always use ‘delete’ for every ‘new’ to manage memory correctly.

Here, Below are examples where we can apply delete operator:

Deleting Array Objects

Deleting array objects in programming is an important concept, and it refers to the process of freeing up memory that was allocated for an array. When you create an array dynamically using memory allocation functions like ‘new‘ in C++ or ‘malloc‘ in C, you need to ensure that you release that memory when you’re done using the array to avoid memory leaks.

Here’s how you do it:

  • Memory Allocation: When you create an array using dynamic memory allocation, you allocate memory on the heap, which is a region of memory separate from the stack where local variables reside.
  • Using the Array: You use the array as needed, performing various operations on its elements.
  • Deletion: After you’re done using the array, it’s crucial to release the memory allocated for it to prevent memory leaks. For this, you use the delete[] operator in C++ and the free() function in C.

In C++:

   int* dynamicArray = new int[5];
   // ... perform operations on the array
   delete[] dynamicArray;

In C:

   int* dynamicArray = (int*)malloc(5 * sizeof(int));
   // ... perform operations on the array

It’s important to note that using delete[] or free() deallocates the memory, making it available for other uses.

Points to Remember:

  • Deleting an array doesn’t delete the array variable itself; it releases the memory it holds.
  • If you forget to delete the dynamically allocated array, it can lead to memory leaks, causing your program to consume more and more memory over time.
  • After the memory is deleted, the values in the array are no longer accessible or valid.
  • Accessing memory after it has been deleted results in undefined behavior and crashes.


using namespace std;

int main() {
    int* dynamicArray = new int[3];

    dynamicArray[0] = 10;
    dynamicArray[1] = 20;
    dynamicArray[2] = 30;

    delete[] dynamicArray; // Deleting the array

    // Accessing the array after deletion will cause undefined behavior
    // dynamicArray[0] = 50;

    return 0;

In this example, the dynamicArray is allocated using new, and then it’s deleted using delete[]. Attempting to access the array after deletion will lead to unpredictable behavior.


(no output, as the program runs successfully without errors)

Deleting NULL pointer

Deleting a NULL pointer is a crucial concept in C++ programming, as it ensures that memory allocated to a pointer is properly freed even if the pointer doesn’t point to any valid memory location. A pointer that doesn’t point to anything is referred to as a NULL pointer. If we try to delete a NULL pointer, nothing will happen, as there’s no memory to release, and it won’t result in any errors or issues.

Here’s a breakdown of how this process works:

Understanding NULL Pointer: In C++, a NULL pointer is a pointer tha˝t doesn’t point to any valid memory location. It’s usually assigned when a pointer is declared but not initialized.

Importance of Deleting NULL Pointers: When we allocate memory dynamically using the new operator, it’s important to clean up the allocated memory using the delete operator. This prevents memory leaks and ensures efficient memory management. However, if a pointer remains uninitialized or is assigned NULL, attempting to delete it will have no effect.

Syntax for Deleting NULL Pointer:

   int* ptr = nullptr; // Declaring a NULL pointer
   delete ptr; // Deleting a NULL pointer

Code Example and Output:

   using namespace std;

   int main() {
       int* ptr = nullptr; // Declare a NULL pointer
       delete ptr; // Deleting a NULL pointer

       cout << "Pointer deleted successfully" << endl;
       return 0;


   Pointer deleted successfully

Safe Practices: It’s always a good practice to set a pointer to NULL after deleting it. This helps avoid accidental use of a deleted pointer, as attempting to access memory through a deleted pointer leads to undefined behavior.

Deleting pointer with or without value

When working with pointers in C++, it’s important to properly manage memory to avoid memory leaks and undefined behavior. Deleting a pointer involves freeing up the memory that the pointer is pointing to. There are two scenarios to consider when deleting pointers: deleting a pointer with a value and deleting a pointer without a value (also known as a null pointer).

Deleting a Pointer with a Value:
When you have a pointer that points to a valid memory address, you can delete it using the delete keyword followed by the pointer’s name. This releases the memory associated with the pointed-to object.

   int *numPtr = new int; // Creating a dynamic integer variable
   *numPtr = 5; // Assigning a value to the dynamic variable

   // Deleting the pointer with a value
   delete numPtr;

   // Now the pointer is not pointing to anything

Output: No specific output, but the memory occupied by the dynamic integer variable is released.

Deleting a Null Pointer:
Deleting a null pointer is safe and has no effect. It’s a good practice to set pointers to null after deleting them to avoid accidental reuse.

   int *emptyPtr = nullptr; // Creating a null pointer

   // Deleting the null pointer (no effect)
   delete emptyPtr;

   // No change, the pointer is still null

Output: No specific output, and the null pointer remains unchanged.

Remember these points when deleting pointers:

  • Always set a pointer to ‘nullptr‘ after deleting it to avoid using it accidentally.
  • Never delete the same pointer more than once. It leads to undefined behavior.
  • Deleting a pointer doesn’t delete the pointer variable itself; it deallocates the memory it points to.
  • When you delete a pointer, any associated resources (like dynamic memory) are released.

Properly managing dynamic memory is crucial in C++ to prevent memory leaks and ensure the efficient use of resources. Always make sure to delete pointers when they’re no longer needed to maintain a clean and well-structured program.

Understand by Detailed Diagram

Horizontal Diagram of using 'delete' Operator in C++
  1. Start: The process begins.
  2. Create a pointer to dynamically allocated memory using ‘new’ operator: A pointer is created, and memory is allocated dynamically using the ‘new’ operator.
  3. Use ‘delete’ operator to deallocate the memory: The ‘delete’ operator is used to free the memory that was previously allocated.
  4. Pointer now points to an undefined location: After deleting the memory, the pointer still exists but points to an undefined location.
  5. End: The process ends.

The Pros and Cons of Using the ‘delete’ Operator

Pros of Using ‘delete’ OperatorCons of Using ‘delete’ Operator
Efficient Memory ManagementCan Cause Memory Leaks
Prevents Memory WastageRequires Proper Usage
Helps Avoid Dangling PointersCan Lead to Undefined Behavior
More Control Over Memory UsageComplex in Some Situations
Reduces the Risk of Memory ErrorsCan Be Tricky for Beginners
The Pros and Cons ‘delete’ Operator

Key Takeaways

  • The ‘delete’ operator is used in C++ to deallocate memory that was previously allocated using the ‘new’ operator.
  • It helps prevent memory leaks by freeing up memory that is no longer needed.
  • Using ‘delete’ properly can improve memory management and reduce memory wastage.
  • It helps avoid dangling pointers, which are pointers that point to memory that has been deallocated.
  • Understanding how to use the ‘delete’ operator is crucial for writing efficient and reliable C++ programs.


In conclusion, the ‘delete’ operator is a crucial part of C++. It allows us to manage our memory efficiently, freeing up space when we no longer need it. So keep practicing, and soon you’ll be a pro at using the ‘delete’ operator!


What is the ‘delete’ operator in C++?
The ‘delete’ operator in C++ is used to free up memory that was previously allocated using the ‘new’ operator.

Why do we use the ‘delete’ operator in C++?
We use the ‘delete’ operator in C++ to manage our memory more efficiently. It allows us to free up space on the heap that we no longer need.

How do we use the ‘delete’ operator in C++?
We use the ‘delete’ operator in C++ by writing ‘delete pointer;’. This frees up the memory that was previously allocated to the pointer.

Can using the ‘delete’ operator cause problems?
Yes, if used incorrectly, the ‘delete’ operator can lead to problems such as dangling pointers and memory leaks. It’s important to understand how the ‘delete’ operator works and when to use it.

What are some examples of using the ‘delete’ operator in C++?
Some examples include using the ‘delete’ operator to delete array objects, deleting a NULL pointer, and deleting pointers with or without values.

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