我想请教一下，这个程序应该怎么改，才能得到正确的答案。

#include"iostream"
using namespace std;
class Student/*构造一个学生类*/
{
private:
    int num;
protected:
    char name[12];
    char sex;
    int age;
public:
    void display()
    {
        cout<<"学号:"<<num<<endl;
        
        cout<<"姓名:"<<name<<endl;
        
        cout<<"性别:"<<sex<<endl;
        
        cout<<"年龄:"<<age<<endl;
        
    }
    void Set_data()
    {
        cout<<"请输入学号:"<<endl;
        cin>>num;
        cout<<"请输入姓名:"<<endl;
        cin>>name;
        cout<<"请输入性别:"<<endl;
        cin>>sex;
        cout<<"请输入年龄:"<<endl;        
        cin>>age;
   
    }
};
class CollegeStudent:private Student/*私有继承学生类*/
{
private:
    char department[20];
    char speciafy[20];
public:
    void display1(CollegeStudent stu1)
    {
        stu1.display();
        cout<<"姓名:"<<name<<endl;
        cout<<"院系:"<<department<<endl;
        cout<<"专业:"<<speciafy<<endl;
    }
    void Set_data1(CollegeStudent &stu2)
    {
        stu2.Set_data();
        
        cout<<"请输入院系:"<<endl;
        cin>>department;
        cout<<"请输入专业:"<<endl;
        cin>>speciafy;
    }
};
void main()
{
    CollegeStudent stu;
    stu.Set_data1(stu);
    stu.display1(stu);
}
运行的时候，没有得到相应的结果。帮忙看一下，谢谢！！