练习42

#include <iostream>
#include <string>
using namespace std;


class Document {
public:
Document() {
}
Document(char *nm);
char *name; // Document name.
void PrintNameOf(); // Print name.
};
Document::Document(char *nm) {
name = new char[strlen(nm) + 1];
strcpy(name, nm);
};
void Document::PrintNameOf() {
cout << name << endl;
}


class Book: public Document {
public:
Book(char *nm, long pagecount);
void PrintNameOf();
private:
long pageCount;
};
Book::Book(char *nm, long pagecount) :
Document(nm) {
pageCount = pagecount;
}
void Book::PrintNameOf() {
cout << "Name of book: ";
Document::PrintNameOf();
}


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