VOID POINTER , NULL POINTER

A void pointer is a special type of pointer. It can point to any data type, from an integer value or a float to a string of characters.

Void pointer limitation is that the pointed data cannot be referenced directly (the asterisk * operator cannot be used on them) since its length is always undetermined.

type casting or assignment must be used to turn the void pointer to a pointer of a concrete data type

 #include <stdio.h>

int main()

{

int a=5,

double b=3.1415;

void *vp;

vp=&a;

printf(“\n a= %d”, *((int *)vp));

vp=&b;

printf(“\n a= %d”, *((double *)vp));

return 0;

}

Output:

a= 5

b= 3.141500

 

NULL POINTER

 A null pointer is a special pointer that points nowhere. That is, no other valid pointer to any other variable or array cell or anything else will ever be equal to a null pointer.

 To initialize a pointer to a null pointer, code such as the following can be used.

 #include <stdio.h>

int *ip = NULL;