Question

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

Answer 1

NULL macro is same as any other macros which will be replaced by its macro body during preprocessor stage of compilation.
Following may be the declaration for NULL Macro depending on the compiler

#define NULL ((char *)0)

or

#define NULL 0L

or

#define NULL 0

NULL Pointer is pointer pointing to NULL location,

int *p=NULL;

Answer 2

http://tech.queryhome.com/123075/what-is-the-difference-between-a-null-pointer-and-null-macro

Answer 3

For me these are as following:

define NULL 0 /* Null macro */

define NULLP (void*)0 /* Null pointer */