Definition of NULL in C and C + + languages

Statement A pointer variable does not automatically allocate any memory.  A null pointer is a pointer that does not point to anything. It can be assigned to a pointer to indicate that the pointer does not point to any position. The consequences of performing an indirect access operation on a null pointer vary depending on the compiler, and two common consequences are a value that returns zero in memory location and a terminating program.  I declare a pointer and assign a value of NULL to see the definition of NULL in VS2013, as follows:

/**/#ifndef null#ifdef __cplusplus#define NULL    0#else  / * __cplusplus */#define NULL    ((void *) 0)#endif/  * __cplusplus */#endif  /* NULL */

It contains some precompiled directives. If NULL is not defined in the preceding code, I define NULL in C + + with a value of 0, otherwise ((void *) 0);  You cannot dereference a null pointer at the same time. 

Definition of NULL in C and C + + languages