1.this 指针
在简单的程序中，类成员函数通常涉及一个对象，但是复杂时有可能涉及两个对象，这种情况就要用到指针。
多说无益，look!

const Stock1& topval(const Stock& s)const;
const Stock& Stock::topval(const Stock& s)const
{
	if (s.total_val > total_val)
		return s;
	else
		return *this;
}

total_val是用来调用该方法的总值，如果if条件成立的话，函数返回指向s的引用，否则将返回用来调用该方法的对象，问题在于如何称呼这个对象，前面的stock并没有别名，这时候我们就要用到this指针了。
topval()里的total_val只不过是this->total_val的简写
看看一种比较完整的代码，此代码缺少主函数

#include <iostream>
#include <string>
using namespace std;
class Stock
{
private:
    std::string company;
    int shares;
    double share_val;
    double total_val;
    void set_tot() { total_val = shares * share_val; }
public:
    Stock();   // default constructor
    Stock(const std::string& co, long n = 0, double pr = 0.0);
    ~Stock(); // do-nothing destructor
    void buy(long num, double price);
    void sell(long num, double price);
    void update(double price);
    void show()const;
    const Stock& topval(const Stock& s) const;
};

// constructors
Stock::Stock() // default constructor
{
    company = "no name";
    shares = 0;
    share_val = 0.0;
    total_val = 0.0;
}

Stock::Stock(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();
}

// class destructor
Stock::~Stock() // quiet class destructor
{
}

// other methods
void Stock::buy(long num, double price)
{
    if (num < 0)
    {
        std::cout << "Number of shares purchased can’t be negative. "
            << "Transaction is 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() const
{
    using std::cout;
    using std::ios_base;
    // set format to #.###
    ios_base::fmtflags orig =
        cout.setf(ios_base::fixed, ios_base::floatfield);
    std::streamsize prec = cout.precision(3);

    cout << "Company: " << company
        << " Shares: " << shares << "\n";
    cout << " Share Price: $" << share_val;
    // set format to #.##
    cout.precision(2);
    cout << " Total Worth: $" << total_val << "\n";

    // restore original format
    cout.setf(orig, ios_base::floatfield);
    cout.precision(prec);
}

const Stock& Stock::topval(const Stock& s) const
{
    if (s.total_val > total_val)
        return s;
    else
        return *this;
}

这串代码包括了析构函数，构造函数，和this指针的应用，笔者可以根据自己思路加上主函数构成一个完整的代码。

2.对象数组

#include <iostream>
const int STKS = 4;
int main()
{
    // create an array of initialized objects
    Stock stocks[STKS] = {
        Stock("NanoSmart", 12, 20.0),
        Stock("Boffo Objects", 200, 2.0),
        Stock("Monolithic Obelisks", 130, 3.25),
        Stock("Fleep Enterprises", 60, 6.5)
    };

    std::cout << "Stock holdings:\n";
    int st;
    for (st = 0; st < STKS; st++)
        stocks[st].show();
    // set pointer to first element
    const Stock* top = &stocks[0];
    for (st = 1; st < STKS; st++)
        top = &top->topval(stocks[st]);
    // now top points to the most valuable holding
    std::cout << "\nMost valuable holding:\n";
    top->show();
    return 0;
}

对象数组是创建一个类的多个对象，其他方面和类没啥区别，这种方法适用于多个对象，比较方便。

3.类作用域
在类中定义的名称（如类数据成员名和类数据函数名）的作用域都为整个类，作用域为整个类的名称在该类中是可知的，在类外是不可知的，因此，不同类中使用相同的类成员名而不会引起冲突，大家懂我的意思吧！
以下是一个案例，比较简单就不分析了。

class Ik
{
private:
   int fuss; // fuss has class scope
public:
   Ik(int f = 9) {fuss = f; } // fuss is in scope
   void ViewIk() const;        // ViewIk has class scope
};

void Ik::ViewIk() const       //Ik:: places ViewIk into Ik scope
{
   cout << fuss << endl;      // fuss in scope within class methods
}
...
int main()
{
   Ik * pik = new Ik;
   Ik ee = Ik(8); // constructor in scope because has class name
   ee.ViewIk(); // class object brings ViewIk into scope
   pik->ViewIk(); // pointer-to-Ik brings ViewIk into scope
...

来看一种错误代码，是一种必须避免的错误，在创建对象前，将没有用于储值的空间，在我们印象中感觉是正确的，但是计算机并不买账。

class Bakery
{
private:
    const int Months = 12; // declare a constant? FAILS
    double costs[Months];
    ...

但是我们有其他方法可以解决这个问题,比如枚举，c++中的static

class Bakery
{
private:
    enum {Months = 12};
    double costs[Months];
    ...

class Bakery
{
private:
    static const int Months = 12;
    double costs[Months];
    ...

4.抽象数据类型
说到ADT
很容易想到栈，c++程序通过栈来管理走动变量，栈存储了多个数据项。
介绍下栈的特征
1.可创建空栈
2.可将数据项添加到堆顶
3.可从栈顶删除数据项
4.可查看栈是否填满
5.可查看栈是否为空

typedef unsigned long Item;

    class Stack
    {
    private:
        enum { MAX = 10 }; // constant specific to class
        Item items[MAX]; // holds stack items
        int top; // index for top stack item
    public:
        Stack();
        bool isempty() const;
        bool isfull() const;
        // push() returns false if stack already is full, true otherwise
        bool push(const Item& item); // add item to stack
        // pop() returns false if stack already is empty, true otherwise
        bool pop(Item& item); // pop top into item
    };
    Stack::Stack() // create an empty stack
    {
        top = 0;
    }

    bool Stack::isempty() const
    {
        return top == 0;
    }

    bool Stack::isfull() const
    {
        return top == MAX;
    }

    bool Stack::push(const Item& item)
    {
        if (top < MAX)
        {
            items[top++] = item;
            return true;
        }
        else
            return false;
    }

    bool Stack::pop(Item& item)
    {
        if (top > 0)
        {
            item = items[--top];
            return true;
        }
        else
            return false;
    }
#include <iostream>
#include <cctype> // or ctype.h
#include<string>
    using namespace std;

    int main()
    {
        using namespace std;
        Stack st; // create an empty stack
        char ch;
        unsigned long po;
        cout << "Please enter A to add a purchase order,\n"
            << "P to process a PO, or Q to quit.\n";
        while (cin >> ch && toupper(ch) != 'Q')
        {
            while (cin.get() != '\n')
                continue;
            if (!isalpha(ch))
            {
                cout << '\a';
                continue;
            }
            switch (ch)
            {
            case 'A':
            case 'a': cout << "Enter a PO number to add: ";
                cin >> po;
                if (st.isfull())
                    cout << "stack already full\n";
                else
                    st.push(po);
                break;
            case 'P':
            case 'p': if (st.isempty())
                cout << "stack already empty\n";
                    else {
                st.pop(po);
                cout << "PO #" << po << " popped\n";
            }
                    break;
            }
            cout << "Please enter A to add a purchase order,\n"
                << "P to process a PO, or Q to quit.\n";
        }
        cout << "Bye\n";
        return 0;
    }

希望大家根据栈的特性多加理解这个例子。