程序代码：

#include"stdio.h"
#include"iostream.h"
#include "string.h"
typedef char string80[80];
class Date
{
public:
    Date() {}
    Date(int y,int m,int d)
    {
    SetDate(y,m,d);
    }
     void SetDate(int y,int m,int d)
     {     Year=y;
        Month=m;
        Day=d;
     }
    string80& GetStringDate(string80 &Date)
    {
    sprintf(Date,"%d/%d/%d",Year,Month,Day);
    return Date;

    }
protected:
    int Year,Month,Day;
};
class Time
{
public:
    Time() {}
    Time(int h,int m,int s)
    {
    SetTime(h,m,s);
    }
     void SetTime(int h,int m,int s)
     {     Hours=h;
        Minutes=m;
        Seconds=s;
     }
    string80& GetStringTime(string80 &Time)
    {
    sprintf(Time,"%d:%d:%d",Hours,Minutes,Seconds);
    return Time;

    }
protected:
    int Hours,Minutes,Seconds;
};
class TimeDate:public Date,public Time
{
public:
    TimeDate():Date() {}
    TimeDate(int y,int mo,int d,int h,int mi,int s):Date(y,mo,d),Time(h,mi,s) {}
    string80&  GetStringDT(string80 &DTstr)
    {
    sprintf(DTstr,"%d/%d/%d;%d:%d:%d",Year,Month,Day,Hours,Minutes,Seconds);
    return DTstr;

    }
};
void main()
{
TimeDate date1,date2(2008,6,5,10,15,05);
string80 DemoStr;
date1.SetDate(2008,9,10);
date1.SetTime(19,07,30);
cout<<"the date1 date and time is:"<<date1.GetStringDT(DemoStr)<<endl;
cout<<"the date1 date is:"<<date1.GetStringDate(DemoStr)<<endl;
cout<<"the date1 time is:"<<date1.GetStringTime(DemoStr)<<endl;
cout<<"the date2 date and time is:"<<date2.GetStringDT(DemoStr)<<endl;
}

string80&  GetStringDT(string80 &DTstr) 这里面第一个&和第二个&分别有什么意思啊 不理解