simple question about the function memcmp in kernel

Dear All:      int memcmp(const void *cs, const void *ct, size_t count) {      const unsigned char *su1, *su2;      int res = 0;      for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)           if ((res = *su1 - *su2) != 0)                break;      return res; } I want to know why it use the temp pointer su1, su2? why it doesn't directly use the cs and ct pointer?