Is type required when using malloc in C?

Possible duplicate:
Can I pass the result to malloc?

I just found out how to use the malloc function, and my teacher noted that when passing a memory address to a pointer, it is necessary to do a type listing. For example, here is the code to get 16 new bytes (4 intervals) using malloc:

#include <stdlib.h>

int main(){
   int *p;
   p = (int *)malloc(4*sizeof(int));

   return 0;
}

My question is: is there an (int *) listing on the right side of the attribution? After all, p is already a pointer to ints, so pointer arithmetic should work fine even without this.

thank