Why is address zero used for the null pointer in C/C++?

In C/C++, a null pointer is a special pointer that does not point to any valid memory location. Address 0 is used for Null Pointers because address 0 is reserved by the system, and it is guaranteed not to be used for valid data.

So, when a pointer is assigned the value 0 (or nullptr), it means the pointer points to nothing.

Some uses of null pointers are:

• To initialize a pointer variable when that pointer variable isn't assigned any valid memory address yet.
• To pass a null pointer to a function argument when we don't want to pass any valid memory address.
• To check for null pointer before accessing any pointer variable. So that, we can perform error handling in pointer related code e.g. dereference pointer variable only if it's not NULL.

In C++ if we assign 0 in any pointer that means the pointer pointing to the NULL.

Initializing a Pointer with Zero

The address zero is reserved to represent a null pointer, and the following syntax shows how to initialize a pointer with a null (zero) address:

Float *p = 0 //initializing the pointer as NULL.

Algorithm

The following is the algorithm to Address Zero is used for Null Pointer in C/C++.

Begin.
   Declare a pointer p of the integer datatype.
      Initialize *p= NULL.
   Print "The value of pointer is".
      Print the value of the pointer p.
End.

Example

In this example, we create a null pointer and prints its value, which generates the output as 0 or nullptr.

#include <stdio.h>
int main() {
   int *p= NULL;//initialize the pointer as null.
   printf("The value of pointer is %p\n", (void*)p);
   return 0;
}

The value of pointer is (nil)

#include<iostream>
using namespace std;
int main() {
    int* p = NULL; // Initialize the pointer as null
    cout<<"The value of pointer is "<<p<<endl;
    return 0;
}

The value of pointer is 0.