大多數情況下，把所有數據指定為私有，以實現信息屏蔽，而把函數指定為公用的。

#include <iostream> 
using namespace std;
class Student {
  private:
    int num;
    int score;
  public:
    void setData() {
      cin >> num;
      cin >> score;
    }
    void display() {
      cout << "num = " << num << endl;
      cout << "score =" << score<<endl;
    }
};
Student stud1, stud2;
int main() {
  stud1.setData();
  stud2.setData();
  stud1.display();
  stud2.display();
  return 0;
}