#include<iostream>
#include<Time.h>
using namespace std;

void  printTime( Time &t)   //  D:\C++\例子\之中.cpp(5) : error C2065: 'Time' : undeclared identifier

class Time
{
    friend void printTime (Time &t);
public:
 Time (int hour ,int min, int sec);
private:
    int m_ihour;
    int m_iminte;
    int m_isecond;
}
int main(void)
{
    Time t(6,34,25);
    printTime(t);

    systerm("pause");
    return 0;
}
void printTime (TIme &t)
cout << t.m_ihour<< ":"<< t.m_iminte << ":" << t.m_isecond <<endl;

根据你的代码原样修改

#include <iostream>
#include <ctime>
using namespace std;

class Time;
void PrintTime( const Time& t );

class Time
{
    friend void PrintTime( const Time& t );
public:
    Time( int hour, int min, int sec ) : m_ihour(hour), m_iminte(min), m_isecond(sec)
    {
    }
private:
    int m_ihour;
    int m_iminte;
    int m_isecond;
};

int main( void )
{
    Time t(6,34,25);
    PrintTime(t);

    return 0;
}

void PrintTime( const Time& t )
{
    cout << t.m_ihour<< ":"<< t.m_iminte << ":" << t.m_isecond <<endl;
}

按照C++风格写代码

#include <iostream>
#include <iomanip>

class Time
{
public:
    Time( int hour, int minute, int second )
        : hour_(hour), minute_(minute), second_(second)
    {
    }
private:
    int hour_;
    int minute_;
    int second_;

    friend std::ostream& operator<<( std::ostream& os, const Time& t );
};

std::ostream& operator<<( std::ostream& os, const Time& t )
{
    char save = os.fill('0');
    os << std::setw(2) << t.hour_ << ':' << std::setw(2) << t.minute_ << ':' << std::setw(2) << t.second_;
    os.fill( save );
    return os;
}

using namespace std;

int main( void )
{
    Time t( 6,34,25 );
    cout << t << endl;

    return 0;
}

我在你原基础上改的；


#include<iostream>
#include<time.h>
using namespace std;

class Time;
void  printTime( Time &t);  

class Time
{
    friend void printTime (Time &t);
public:
    Time (int hour ,int min, int sec)
    {
        m_ihour=hour;
        m_iminte=min;
        m_isecond=sec;
    };
private:
    int m_ihour;
    int m_iminte;
    int m_isecond;
};

void printTime (Time &t)
{
    cout << t.m_ihour<< ":"<< t.m_iminte << ":" << t.m_isecond <<endl;
}
int main(void)
{
    Time t(6,34,25);
    printTime(t);
   
    system("pause");
    return 0;
}


构造函数要把值赋给成员变量。

这个程序楼主要实现的功能其实就是把输入的三个数字用冒号隔开再输出。可以写得更简单的，也不用包含time.h