pointer to constant: If a pointer is pointing to constant it is called as pointer to constant.In this case we cannot change the content of constant.

eg :  const int n=5;

  int *p=&n;

in this case we cannot change the value of n.

constant pointer:  If we declare a pointer as constant we can change the contents of memory pointed by pointer.But we cannot change the pointer value i.e incrementing or decrementing of pointer address.

Eg : const int *p=n;

Here we can change the content of n,but we cannot increment or decrement of pointer p(p++ or ++p).