C++ 类与对象关系、生成

#include <iostream>
class student {
public:
  int No;
  int Score;
public:
  void setScore(int s) {
  Score = s;
  }
  int getScore() {
  return Score;
  }
  void setNo(int n) {
  No = n;
  }
  int getNo() {
  return No;
  }
};
int main(int argc, char *argv[])
{
  student s1;
  student s2;
  s1.setNo(1);
  s2.setNo(2);
  std::cout << s1.getNo() << std::endl;
  std::cout << s2.getNo() << std::endl;
  student *pS1;
  pS1 = new student;
  pS1->setNo(3);
  std::cout << pS1->getNo() << std::endl;
  return 0;
}