定义一个Document类，有数据成员name, 从Document类派生出Book类，增加数据成员pageCount。 主函数已经提供如下，请勿修改： int main() { Document a("Document1"); Book b("Book1", 100); a.PrintNameOf(); b.PrintNameOf(); }

可以按照如下方式定义Document类和Book类：

#include <iostream>
#include <string>

using namespace std;

class Document {
public:
    Document(string name): name(name) {}
    void PrintNameOf() const {
        cout << "This document is named " << name << endl;
    }
private:
    string name;
};

class Book : public Document {
public:
    Book(string name, int pageCount): Document(name), pageCount(pageCount) {}
    void PrintNameOf() const {
        cout << "This book is named " << name << " and has " << pageCount << " pages." << endl;
    }
private:
    int pageCount;
};

在主函数中，可以这样使用：

int main() {
    Document a("Document1");
    Book b("Book1", 100);
    a.PrintNameOf();
    b.PrintNameOf();
    return 0;
}

输出结果为：

This document is named Document1
This book is named Book1 and has 100 pages.