error C2065: 'set_time' : undeclared identifier是什么意思？

[wweilinux]

代码如下：

#include <iostream>
using namespace std;

class Time
{
public:
void set_time();
void show_time();
private:
int hour;
int minute;
int sec;
};

int main()
{
Time t1;
set_time();
show_time();
system("pause");

Time t2;
set_time();
show_time();
system("pause");

return 0;
}

void Time::set_time()
{
cin>>hour;
cin>>minute;
cin>>sec;
}

void Time::show_time()
{
cout<<hour<<":"<<minute<<":"<<sec<<endl;
}

编译提示：

d:\vc\project\console\8_1\8_1.cpp(18) : error C2065: 'set_time' : undeclared identifier
d:\vc\project\console\8_1\8_1.cpp(19) : error C2065: 'show_time' : undeclared identifier

是什么意思？怎么解决？

[「已注销」]

#include <iostream>
using namespace std;

class Time
{
public:
void set_time();
void show_time();
private:
int hour;
int minute;
int sec;
};

int main()
{
Time t1;
t1.set_time();
t1.show_time();
system("pause");

Time t2;
t2.set_time();
t2.show_time();
system("pause");

return 0;
}

void Time::set_time()
{
cin>>hour;
cin>>minute;
cin>>sec;
}

void Time::show_time()
{
cout<<hour<<":"<<minute<<":"<<sec<<endl;
}

[「已注销」]

Time t1;
set_time();
show_time();
system("pause");

Time t2;
set_time();
show_time();
system("pause");
------------------------------
set_time();
show_time();这俩个是成员函数。。要通过实例对象来引用。。