Some notes on pointers in C

Note the following simple program and Its output on GCC 3.2.3:

#include 
#include 

int main(void)
{
 int *p;
 printf("%p %i\n",p, *p);
 
 int *p2 = malloc(sizeof(*p2));
 printf("%p %i\n",p2, *p2);
 
 int *p3 = NULL;
 printf("%p \n",p3);
 
 p3 = malloc(sizeof(*p3));
 printf("%p %i\n",p3, *p3);
 return 0;
}

The output is:

0x8048414 1474660693
0x8d3d008 0
(nil) 
0x8d3d018 0

So, when you declare a pointer, it points to some garbage data.
When you malloc memory, the pointer points to some memory-allocated location.
When you assign NULL to a pointer, it becomes NULL Pointer and its address is NULL, and you need to reallocate memory for before use.

So,