一个小函数，就是从文件里面读取的数据不是原来的数据，请各位大侠们看看，很短的。

void student::readdate()//从文件读取数据
{
    class student *p1, *p2;
    ifstream infile("f1.txt",ios::in);
    if (!infile)
    {
        cout<<"文件打开错误！";
        return ;
    }
    infile>>totall_num;
    head=p1=p2=new class student;
    infile>>p1->num;
    infile>>p1->name;
    infile>>p1->birthday;
    infile>>p1->age;
    infile>>p1->dizhi;
    infile>>p1->dianhua;
    infile>>p1->youbian;
    infile>>p1->E_mail;
    while(infile!=0)
    {
        
        p1=new class student;
        infile>>p1->num;
        infile>>p1->name;
        infile>>p1->birthday;
        infile>>p1->age;
        infile>>p1->dizhi;
        infile>>p1->dianhua;
        infile>>p1->youbian;
        infile>>p1->E_mail;
        p2->next=p1;
        p2 = p1;
    }
    p2->next=NULL;
    infile.close();
    totall_num=i;
   
   
}