NULL Pointer in C: Definition and Usage

Null Pointer 

• NULL Pointer is a pointer which is pointing to nothing.
• The NULL pointer points the base address of the segment.
• In case, if you don’t have an address to be assigned to a pointer then you can simply use NULL
• The pointer which is initialized with the NULL value is considered as a NULL pointer.
• NULL is a macro constant defined in following header files –

stdio.h

alloc.h

mem.h

stddef.h

stdlib.h

Defining NULL Value

#define NULL 0

Below are some of the variable representations of a NULL pointer.

float *ptr  = (float *)0;
char  *ptr  = (char *)0;
double *ptr = (double *)0;
char *ptr   = '\0';
int *ptr    = NULL;

Example of NULL Pointer

#include 
int main()
{
   int  *ptr = NULL;
   printf("The value of ptr is %u",ptr);

   return 0;
}

Output :

The value of ptr is 0

#define NULL 0