对象和类，公有类和私有类，构造函数和析构函数，const成员函数，this指针，对象数组，类作用域，抽象数据

下面是头文件stock00.h的内容：

#ifndef STOCK00_H_#define STOCK00_H_#include<string>class Stock{PRivate://私有，不可以被外界直接访问，只能通过公有函数访问	std::string company;	long shares;	double share_val;	double total_val;	void set_tot() { total_val = shares*share_val; }public://公有，可以被外界直接访问	void acquire(const std::string&co, long n, double pr);	void buy(long num, double price);	void sell(long num, double price);	void update(double price);	void show();};#endifprivate是类对象默认访问控制。
接下来的file1是函数的定义：
#include<iostream>//此文件是对头文件中的函数定义#include"stock00.h"void Stock::acquire(const std::string&co, long n, double pr){	company = co;	if (n < 0)	{		std::cout << "Number of shares can't be negative;"			<< company << "shares set to 0./n";		shares = 0;	}	else		shares = n;	share_val = pr;	set_tot();}void Stock::buy(long num, double price){	if (num < 0)	{		std::cout << "Number of shares purchased can't be negative."			<< "Transaction if aborted./n";	}	else	{		shares += num;		share_val = price;		set_tot();	}}void Stock::sell(long num, double price){	using std::cout;	if (num < 0)	{		cout << "Number of shares sold can't be negative."			<< "Transaction is aborted./n";	}	else if(num>shares)	{		cout << "You can't sell more than you have!"			<< "Transaction is aborted./n";	}	else	{		shares -= num;		share_val = price;		set_tot();	}}void Stock::update(double price){	share_val = price;	set_tot();}void Stock::show(){	std::cout << "Company:" << company		<< " Shares: " << shares << '/n'		<< "Share price :$" << share_val		<< " Total Worth: $" << total_val << std::endl;}