In C++, we can use the **`free()` function** to deallocate a memory block, making it available for further allocations. 

The memory can be allocated beforehand using the `calloc()`, `malloc()`, or `realloc()` functions. It does not change the `value` of the pointer and points to the exact memory location. 

# Syntax

``` c++
void free(void* ptr);
```

## `ptr`

* This represents the pointer to an allocated memory block. 

* If `ptr` is `null`, `free()` does nothing.

* If `ptr` is not pointing to an allocated memory block, `free()` causes undefined behavior.

# Return value

- The function `free()` returns `None`.

# Required headers

The function `free()` requires the following header to work properly:

``` c++
#include <cstdlib>
```

//Including headers
#include <cstdlib>
#include <iostream>
using namespace std;

int main() {

   //Allocating memory block
   int* ptr = (int*)calloc(3, sizeof(int));
   int* ptr1 = (int*)malloc(3*sizeof(int));
   int* ptr2;
   ptr2 = (int*)realloc(ptr2,3*sizeof(int));
   
   //Deallocating allocated memory
   free(ptr);
   free(ptr1);
   free(ptr2);

   return 0;
}

How to use free() in C++

Utilize free() to deallocate memory in C++; it needs #include <cstdlib> and accepts a pointer to allocated memory.

How to use free() in C++

Syntax

ptr

Return value

Required headers

Code

`ptr`