Dangling pointer

A pointer pointing to a memory location that has been deleted (or freed) is called dangling pointer.

// Deallocating a memory pointed by ptr causes 
// dangling pointer 
#include <stdlib.h> 
#include <stdio.h> 
int main() 
{ 
    int *ptr = (int *)malloc(sizeof(int)); 
  
    // After below free call, ptr becomes a  
    // dangling pointer 
    free(ptr);  
      
    // No more a dangling pointer 
    ptr = NULL; 
}