又是关于类的。

请帮忙解释下注释的那一条语句，就一条，非常感谢 。
单冒号的作用...

#include<iostream.h>
#include<string.h>
const int LEN=50;
class Station
{
protected:
    char from_station[LEN];
    char to_station[LEN];
public:
    Station(char fs[],char ts[])
    {
        strcpy(from_station,fs);
        strcpy(to_station,ts);
    }
    void input_value()
    {
        cout<<"Enter from station:"<<endl;
        cin>>from_station;
        cout<<"Enter to station:"<<endl;
        cin>>to_station;
    }
    void display()
    {
        cout<<"Going from "<<from_station<<"station to "<<to_station<<" station";
    }
};
class Mile
{
protected:
    int mile;
public:
    Mile(int m)
    {
        mile=m;
    }
    void input_mile()
    {
        cout<<"Enter mile:";
        cin>>mile;
    }
    void display()
    {
        cout<<" is"<<mile<<" miles";
    }
};
class Price:public Station,public Mile
{
    int price;
public:
    Price(char ff[],char tt[],int mm,int pp):Station(ff,tt),Mile(mm)//就是这里，中间的冒号起什么作用？这类型的定义是什么格式来的？
    {
    price=pp;    
    }
    void getprice()
    {
        Station::input_value();
        Mile::input_mile();
        cout<<"Enter price:";
        cin>>price;
    }
    void display()
    {
        Station::display();
        Mile::display();
        cout<<" The price is "<<price<<endl;
    }
};
void main()
{
    Price A("Beijing","Xia men",1400,50);
    A.display();
}

[ 本帖最后由 XIAO荣 于 2009-8-17 16:19 编辑 ]