#include <stdio.h>
int main ()
{
int *ptr = NULL;
printf(“The value of ptr is : %x\n”, ptr );
return 0;
}
The value of ptr is 0
On most of the operating systems, programs are not permitted to access memory at address 0 because that memory is reserved by the operating system. However, the memory address 0 has special significance; it signals that the pointer is not intended to point to an accessible memory location. But by convention, if a pointer contains the null (zero) value, it is assumed to point to nothing.
To check for a null pointer you can use an, if statement as follows :
if(ptr) /* succeeds if p is not null */
if(!ptr) /* succeeds if p is null */