#include<iostream.h>
#define N 20
#include<string.h>
class object
{
char name[N];
int no;
public:
object(char na[N],int num);

};
class Book: public object
{
char author[20];
public:

Book(char na[N],int num,char zuozhe[N]);

Book();
void setBook(char na[N],int num,char zuozhe[N]);

};
object::object(char na[N],int num)
{
strcpy(name,na);
no=num;
}
Book::Book(char na[N],int num,char zuozhe[N]):object(na[N],num)
{
strcpy(author,zuozhe);
}

class Reader:public object
{
public:
Reader(char na[N],int num):object(na[N],num)
{
cout<<"读者： "<<name[N]<<"("<<no<<")"<<endl;
cout<<"所借图书："<<endl;
}

Reader();
void setReader(char na[N],int num)
{
strcpy(object::name,na);object::no=num;
cout<<"读者： "<<object::name<<"("<<object::no<<")"<<endl;
cout<<"所借图书："<<endl;
}

void rentBook(Book &a)
{
static int n=1;
cout<<" "<<n<<". ";
n++;
cout<<a.name<<"("<<a.no<<")"<<endl;
}
};

void main()
{
Book b1("C语言", 1,"潭浩强"),b2("数据结构", 2,"严蔚敏"),b3,b4,b5;
Reader r1("王华",1),r2;
b3.setBook("VB程序设计",3, "成功");
b4.setBook("数据库原理",4, "王瑟");
b5.setBook("计算机导学",5, "张仁");
r2.setReader("李明",2);
r1.rentBook(b1);
r1.rentBook(b3);
r2.rentBook(b2);
r2.rentBook(b4);
r2.rentBook(b5);
}

你说什么地方有错误呢?

问题在这里：

object::object(char na[N],int num)
{
strcpy(name,na);
no=num;
}
Book::Book(char na[N],int num,char zuozhe[N]):object(na[N],num)
{
strcpy(author,zuozhe);
}

object的构造函数的第一个参数是一个数组．
na[N]则是代表数组中的第Ｎ个元素．
所以发生编译错误．

#include<iostream.h>
#define N 20
#include<string.h>
class object
{

public:
object(char na[N],int num);
object();
char name[N];//我不知道怎么回事 用Private会报错
int no;

};
class Book: public object
{
char author[20];
public:

Book(char na[],int num,char zuozhe[]);

Book();
void setBook(char na[N],int num,char zuozhe[N]);

};
object::object() {}//开始没有空参数的构造函数 可是后面又用了
object::object(char na[N],int num)
{
strcpy(name,na);
no=num;
}

Book::Book (): object(){}
Book::Book(char na[N],int num,char zuozhe[N]):object(na,num)同楼上
{
strcpy(author,zuozhe);
}

class Reader:public object
{
public:
Reader(char na[N],int num):object(na,num)
{
cout<<"读者： "<<name[N]<<"("<<no<<")"<<endl;
cout<<"所借图书："<<endl;
}

Reader(){};
void setReader(char na[N],int num)
{
strcpy(object::name,na);object::no=num;
cout<<"读者： "<<object::name<<"("<<object::no<<")"<<endl;
cout<<"所借图书："<<endl;
}

void rentBook(Book &a)
{
static int n=1;
cout<<" "<<n<<". ";
n++;
cout<<a.name<<"("<<a.no<<")"<<endl;
}
};

void main()
{
Book b1("C语言", 1,"潭浩强"),b2("数据结构", 2,"严蔚敏"),b3,b4,b5;
Reader r1("王华",1),r2;
//b3.setBook("VB程序设计",3, "成功");//你的book类里没有这个函数
//b4.setBook("数据库原理",4, "王瑟");
//b5.setBook("计算机导学",5, "张仁");
r2.setReader("李明",2);
r1.rentBook(b1);
r1.rentBook(b3);
r2.rentBook(b2);
r2.rentBook(b4);
r2.rentBook(b5);
}

没有默认的构造函数