What is the difference between a NULL Pointer and a NULL Macro?

Question

What is a NULL Macro? What is the difference between a NULL Pointer and a NULL Macro?

Answer 1

Null macro is defined in stdio.h and stddef.h.It is used to represent a null pointer in code. its value is zero.

Null pointer is a pointer which has 0 or NULL value stored and points to points to 0x00 i.e. the first memory location of the OS.
A null pointer should not be confused with an uninitialized pointer.

Comments

thanks for the answers.
Hey Can you explain when to use NULL macro.

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Consider the sample 'C' program to demonstrate utilities of NULL macro

#include <stdio.h>      /* printf, scanf, NULL */
#include <stdlib.h>     /* malloc, free */

int main ()
{
  int i,len;
  char * buffer;

  printf (" string length?");
  scanf ("%d", &len);

  buffer = (char*) malloc (len+1);
  if (buffer == NULL)
        exit (1);

  for (i=0; i<len; i++)
    buffer[i]='i'+i;
  buffer[len]='\0';    //or buffer[len]=NULL is also valid

  printf ("string: %s\n",buffer);
  free (buffer);
  buffer = NULL;
}