这是我的main函数
#include<iostream>
#include<cstring>
#include"student.h"
#include"birthday.h"
using namespace std;

int  main ()
{

    char name[20],num[20],id[20],sex;
    int year,month,day;

    cin>>year>>month>>day;
    bir student_bir(year,month,day);

    cin>>name>>num>>id>>sex;
    student student_ip(name,num,sex,id);//这里说我student为error C2065: 'student' : undeclared identifier我的这个类在头文件#include"student.h"中 。。。为什么这样说我错了啊！
    student student_ip(student_bir);

    student_ip.show();
   
    return 0;
}

头文件#include"student.h"
#include<iostream>
using namespace std;
#include"birthday.h"
#ifdef _STUDENT_H_
#define _STUDENT_H_
class student{
public:
    student(char *nam,char *nu,char a,char * d);
    student(student &p);
    student(bir p1);
    ~student(){}   
    void show();
private:
    char name[20], number[20],sex,id[20];
    bir p2;
    static  int count;
};
#endif

[ 本帖最后由 李雪莲 于 2013-4-4 16:19 编辑 ]

class Program
    {
        class Book:IComparable//继承接口，用来重写方法
        {
            private string bookname;
            private string bookkind;
            private decimal bookprice;
            public string BookName
            {
                set { bookname = value; }
                get { return bookname; }
            }
            public string BookKind
            {
                set { bookkind = value; }
                get { return bookkind; }
            }
            public decimal BookPrice
            {
                set { bookprice = value; }
                get { return bookprice; }
            }
            public int CompareTo(object obj)//重写CompareTo方法，使Book类可以使用数组的排序功能
            {
                Book book = (Book)obj;
                if (this.bookprice < book.bookprice)
                    return -1;
                if (this.bookprice > book.bookprice)
                    return 1;
                return 0;
            }
        }

 static void Main(string[] args)
        {
            {
                int[] price=new int[]{10,40,30,50,10};
                Book[] books = new Book[5];//定义一个book类型的数组
                for (int i = 0; i < books.Length;i++ )//为数组赋值，这里只写了价格，可以自己添加分类和书名
                {
                    books[i]=new Book() ;
                    books[i].BookPrice = price[i];
                }
                Array.Sort(books);//进行排序
                foreach (Book book in books)
                {
                    Console.WriteLine(book.BookPrice);
                }
}

谢谢！！