1 struct complex {
   2     double real;
   3     double imag;
   4 };
   5 complex add(complex a, complex b); 
   6 complex substract(complex a, complex b);
   7 complex multiply(complex a, complex b);
   8 void display(complex a);
   9 void set(complex *c, double r, double i);
  10 
  11 int main() {
  12     complex x, y;
  13     set(&x, 10.0, 20.0);
  14     set(&y, 1.0, -2.0);
  15     complex z = add(x, y);
  16     display(z);
  17 }

   1 struct clock {
   2     int second;
   3     int minute;
   4     int hour;
   5 };
   6 void set_time( clock *c, int h, int m, int s) {
   7     c->second = s;
   8     c->minute = m;
   9     c->hour = h;
  10 }
  11 void show_time(const clock *c) {
  12     cout << c->hour << c->minute << c->second;
  13 }
  14 void inc_second(clock *c) {
  15     c->second ++;
  16     if(c->second == 60) {
  17         c->minute ++;
  18         c->second = 0;
  19         if(c->minute == 60) {
  20             c->hour ++;
  21             c->minute = 0;
  22             if(c->hour == 24)
  23                 c->hour = 0;
  24         }
  25     }
  26 }
  27 
  28 int main() {
  29     clock c;
  30     set_time(&c, 10, 10, 30);
  31     inc_second(&c);
  32     show_time(&c);
  33 }

   1 #define MALE true
   2 #define FEMALE false
   3 struct student{
   4    char num[20];
   5    char name[10];
   6    bool gender;
   7 };
   8 void set(student &s, char id[], char n[], bool g){
   9     strcpy(s.num, id);
  10     strcpy(s.name, n);
  11     s.gender = g;
  12 }
  13 void display(student &s) {
  14     cout << s.num << s.name << (s.gender?"male":"female");
  15 } 
  16 int main() {
  17     student stud1, stud2;
  18     set(stud1, "110101", "Rose", FEMALE);
  19     set(stud2, "110102", "JACK", MALE);
  20     display(stud1);
  21     display(stud2);
  22 }

   1 struct clock {
   2     int  hour, minute, second;
   3     void set_time(int h, int m, int s);
   4     void show_time();
   5     void inc_second();
   6 };

   1 struct clock {
   2     int  hour, minute, second;
   3     void set_time(int h, int m, int s) {
   4         hour = h;
   5         minute = m;
   6         second = s;
   7     }
   8     void show_time() {
   9         cout << hour << minute << second;
  10     }
  11     void inc_second(clock *c) {
  12         second ++;
  13         if(second == 60) {
  14             minute ++;
  15             second = 0;
  16             if(minute == 60) {
  17                 hour ++;
  18                 minute = 0;
  19                 if(hour == 24)
  20                     hour = 0;
  21             }
  22         }
  23     }
  24 };
  25 
  26 int main() {
  27     clock c1, c2;
  28     c1.set_time(10, 10, 30);
  29     c2.set_time(18, 00, 00);
  30     c1.show_time();
  31     c2.show_time();
  32 }

   1 //clock.h头文件:
   2 struct clock {
   3     int  hour, minute, second;
   4     void set_time(int h, int m, int s);
   5     void show_time();
   6     void inc_second();
   7 };
   8 
   9 //clock.cpp源文件:
  10 void clock::set_time(int h, int m, int s) {
  11     hour = h;
  12     minute = m;
  13     second = s;
  14 }
  15 void clock::show_time() {
  16     cout << hour << minute << second;
  17 }
  18 void clock::inc_second() {
  19     second ++;
  20     if(second == 60) {
  21         minute ++;
  22         second = 0;
  23         if(minute == 60) {
  24             hour ++;
  25             minute = 0;
  26             if(hour == 24)
  27                 hour = 0;
  28         }
  29     }
  30 }
  31 
  32 
  33 
  34 // main.cpp源文件
  35 int main() {
  36     clock c1, c2;
  37     c1.set_time(10, 10, 30);
  38     c2.set_time(18, 00, 00);
  39     c1.show_time();
  40     c2.show_time();
  41 }

   1 const bool MALE = true;
   2 const bool FEMALE = false;
   3 struct student{
   4    string num;
   5    string name;
   6    bool gender;
   7    void set(string id, string n, bool g) {
   8        num = id;
   9        name = n;
  10        gender = g;
  11    }
  12    void diplay() {
  13        cout << num << name << (gender?"male":"female");
  14    }
  15 };
  16 int main() {
  17    student stud1, stud2;
  18    stud1.set("110101", "Rose", FEMALE);
  19    stud2.set("110102", "Jack", MALE);
  20    stud1.display();
  21    stud2.display();
  22 }

   1 int main() {
   2    struct clock now;      // 类似于C语言结构体
   3    clock next;            // struct可以省略
   4    next.hour = 10;         // 同C语言结构体类似，可以访问成员
   5    next.minute = 10;
   6    next.second = 30;
   7    now.set_time(9, 40, 0); // 可以用类似的方式调用成员函数
   8    now.show_time();
   9    next.show_time();
  10 }

   1 void f() {
   2     clock * my_clock = new clock; //分配对象
   3     clock * now = new clock;
   4     now->hour = 10;          //通过指针访问成员
   5     now->minute = 10;
   6     now->second = 30;  
   7     my_clock->set_time (9, 40, 0); //通过指针调用成员函数
   8     my_clock->show_time();
   9     delete my_clock;              //释放对象
  10     delete now;
  11 }

   1 int main() {
   2     clock clocks[100]; // 类似于int array[100];
   3     clocks[0].set_time(9, 10, 25);
   4     clocks[1].set_time(9, 9, 13);
   5     clocks[2].set_time(9, 12, 25);
   6     // ... ...
   7     clock *pc = new clock[100];
   8     pc[0].set_time(11, 20, 30);
   9     // ... ...
  10 }

   1 struct clock {
   2     int second, minute, hour;
   3     inline void show_time() { //inline may be omitted
   4         cout << hour << minute << second;
   5     }
   6 };

   1 struct clock {
   2     int second, minute, hour;
   3     inline void show_time();
   4 };
   5 inline void Clock::show_time() {
   6     cout << hour << minute << second;
   7 }

   1 struct clock {
   2     int second, minute, hour;
   3     void set_time(int h, int m) {
   4         hour = h;
   5         minute = m;
   6         second = 0;
   7     }
   8     void set_time(int h) {
   9         hour = h;
  10         minute = second = 0;
  11     }    
  12 };
  13 int main() {
  14     clock t;
  15     t.set_time( 10, 30);
  16     t.set_time( 10 );
  17 }

   1 struct clock {
   2     int second, minute, hour;
   3     void set_time(int h =0, int m=0, int s=0);
   4 };
   5 void clock::set_time(int h, int m, int s) {
   6     hour = h;  
   7     minute = m; 
   8     second = s;
   9 }

   1 class clock {
   2 private: //只能在类内访问
   3     int hour, minute, second;  
   4 public:  //可以在类外访问
   5     void set_time(int h, int m, int s);
   6     void show_time();
   7 };

   1 int main(){
   2     clock d;
   3     d.set_time(8, 27, 30);  // 类内访问public, ok
   4     d.hour = 10;           // 类内访问private错误
   5 }
   6 void clock::set_time(int h, int m, int s) {
   7     hour = h;    //类内访问private, ok
   8     minute = m;
   9     second = s;
  10 }

   1 struct clock_a {
   2     void set_time(int h, int m, int s); // public here
   3 private:
   4     int hour, minute, second; //private here
   5 };
   6 
   7 class clock_b {
   8     int hour, minute, second; // private here;
   9 public:
  10     void set_time(int h, int m, int s); // public here;
  11 };

   1 class student{
   2 private:
   3     string num;
   4     string name;
   5     bool gender;
   6 public:
   7     void display() {
   8         cout << num << name << (gender?"male":"female");
   9     }
  10     void setnum(string n) {
  11         num = n;
  12     }
  13     void setname(char n) {
  14         name = n;
  15     }
  16     void setgender(bool g) {
  17         gender = g;
  18     }
  19 };
  20 
  21 int main() {
  22     student stud1;
  23     stud1.setname("jack");
  24     stud1.setnum("05020001");
  25     stud1.setgender(true);
  26     stud1.display();
  27     cout << stud1.gender;  //error
  28 }

   1 class clock {
   2 private: //只能在类内访问
   3     int hour, minute, second;  
   4 public:  //可以在类外访问
   5     void add(int s) {
   6         for(int i = 0; i < s; i++) 
   7             inc();
   8     }
   9 private:
  10     void inc() {
  11         second++;
  12         if(second == 60) {
  13             second = 0;
  14             minute ++;
  15             if(minute == 60) {
  16                 minute = 0;
  17                 hour++;
  18                 if(hour == 24)
  19                     hour = 0;
  20             }
  21         }
  22     }
  23 };

   1 int main() {
   2     int i;  // 定义普通变量
   3     cout << i;  // 访问变量，错误，没有初始化
   4     clock time; // 定义对象，定义的同时并没有初始化
   5     time.show_time();          //错误，没有初始化
   6     time.set_time(20, 55, 10); //需要调用初始化函数后
   7     time.show_time();          //才能够访问
   8 }

   1 int main() {
   2     int i = 5;  // 定义普通变量，并初始化
   3     cout << i;  // 访问变量，ok
   4 }

   1 int main() {
   2     clock c1(10,10, 30); // 定义对象，定义的同时并且初始化
   3     clock c2 = clock(10, 10, 31); // 或者这样初始化
   4     c1.show_time();
   5 }

   1 class clock{
   2     int hour, minute, second;
   3 public:
   4     /*构造函数，函数名与类名相同，没有返回类型*/
   5     clock(int h, int m, int s){
   6         hour = h;
   7         minute = m;
   8         second = s;
   9     }
  10     void show_time() {
  11         cout << hour << minute << second;
  12     }
  13 };

   1 class clock{
   2 public:
   3     void clock (/*...*/); // error
   4 };

   1 int main() {
   2     clock c1; // 语法错误，没有这样的构造函数
   3     c1.show_time();
   4 }

   1 class clock{
   2     int hour, minute, second;
   3 public:
   4     clock() {
   5         hour = minute = second = 0;
   6     }
   7     void show_time() {
   8         cout << hour << minute << second;
   9     }
  10 };
  11 
  12 int main() {
  13     clock c1; // 初始化为0时0分0秒
  14     c1.show_time();
  15     clock c2(15, 30, 0) // 错误，没有这样的构造函数
  16     clock c3(); // 定义函数而不是定义对象
  17 }

   1 class clock {
   2     int hour, minute, second;
   3 public:
   4     clock(int h, int m=0, int s=0);
   5     clock(); // default constructor默认构造函数
   6     clock(const char *s);
   7 };

   1 int main() {
   2     clock now;  //默认构造now对象call default constructor
   3     clock getup(6, 30, 30); 
   4     clock early(6);
   5     clock sleep("23:30:0");
   6     clock lesson(9, 21);
   7 }

   1 class clock {
   2     int hour, minute, second;
   3 public:
   4     clock(int h =0, int m = 0, int s=0);
   5 };
   6 int main() {
   7     clock c1;
   8 }

   1 class clock{
   2     int hour, minute, second;
   3 public:
   4     clock(int h, int m, int s);
   5 };
   6 clock::clock( int h, int m, int s) {
   7     hour = h;
   8     minute = m;
   9     second = s;
  10 }
  11 
  12 int main() {
  13     clock sleep(22, 30, 0);
  14     clock getup(6, 30, 30); 
  15     clock now = clock(9, 21, 20);
  16     clock *pC = new clock(23, 30, 25); //构造函数会被自动调用
  17 }

   1 int main() {
   2     clock *pc = new clock(23, 30, 25); // 构造函数被掉用了
   3     clock *pd = (clock *)malloc(sizeof(clock)); //构造函数没有调用
   4 }

   1 class clock {
   2     int hour, minute, second;
   3 public:
   4     clock(int h =0, int m = 0, int s=0) {
   5         hour = h;
   6         minute = m;
   7         second = s;
   8     }
   9 };
  10 void f() {
  11     clock cls[10];
  12     clock *p = new clock[10];
  13 }

   1 class clock {
   2     int hour, minute, second;
   3 public:
   4     clock(int h , int m, int s) {
   5         hour = h;
   6         minute = m;
   7         second = s;
   8     }
   9 };
  10 void f() {
  11     clock cls[10] = {clock(0,0,0), clock(1,0,0), clock(2,0,0), clock(3,0,0), clock(4,0,0), clock(5,0,0), clock(6,0,0), clock(7,0,0), clock(8,0,0), clock(9,0,0), clock(10,0,0)};
  12     clock *p = new clock[10]; // 错误，没有办法初始化
  13 }

   1 class clock{
   2     const int hour, minute, second;
   3 public:
   4     clock(int h, int m, int s) {
   5          hour = h; // 错误，const变量不能够赋值
   6          minute = m; // 错误
   7          second = s; // 错误
   8     }
   9     void show_time() {
  10         cout << hour << minute << second;
  11     }
  12 };

   1 class clock{
   2     const int hour, minute, second;
   3 public:
   4     clock(int h, int m, int s) 
   5         : hour(h), minute(m), second(s) {
   6     }
   7     void show_time() {
   8         cout << hour << minute << second;
   9     }
  10 };

   1 class clock{
   2     int hour, minute, second;
   3 public:
   4     clock(int h, int m, int s) 
   5         : hour(h), minute(m), second(s) {
   6     }
   7     void show_time() {
   8         cout << hour << minute << second;
   9     }
  10 };

   1 class world_clock {
   2     clock c;
   3     int timezone;
   4 public:
   5     world_clock(int hour, int minute, int second, int t)  
   6         :c(hour, minute, second), timezone(t) {
   7     }
   8 };

   1 class world_clock {
   2 private:
   3     clock c;
   4     int timezone;
   5 public:
   6 };
   7 
   8 int main() {
   9     world_clock wc; // wc.timezone没有初始化，但是wc.c的构造函数会自动调用
  10 }

   1 class clock {
   2     int hour, minute, second;
   3 public:
   4     ~clock() {
   5         //作一些资源释放操作
   6     }
   7 };

   1 int main() {
   2     clock d1(4, 11, 1);
   3     if( true ){
   4         clock *d2 = new clock(9, 9, 9);
   5         clock d3(8, 10,0);
   6         //…
   7     } // d3 is destructed here
   8     delete d2; // d2 is destructed here
   9     clock d4;
  10 }  // d1,d4 is destructed here
  11 

   1 class mystring{
   2     char *s;
   3 public:
   4     mystring(char *str) {
   5         s = new char[strlen(str)+1];
   6         strcpy(s, str);
   7     }
   8     ~mystring() {
   9         delete[] s;
  10     }
  11 };
  12 int main() {
  13     mystring s("Hello");
  14 }

   1 int main() {
   2     clock *d1 = new clock ;
   3     clock *d2 = new clock ( 10, 11, 1);
   4     clock *d3 = new clock [ 1000 ];
   5     clock *d4 = (clock *)malloc( sizeof(clock) ); // 没有初始化
   6     delete d1;
   7     delete d2;
   8     delete[] d3;
   9     free(d4);
  10 }

   1 void display( clock d ) {
   2    //...
   3 } 
   4 
   5 int main() {
   6     clock now;      //默认构造函数
   7     clock d = now;  //拷贝构造
   8     clock s( now ); //拷贝构造
   9     d = s; //赋值
  10     display(s);            //拷贝构造
  11 ｝

   1 class clock {
   2     int hour, minute, second;
   3 public:
   4     clock(int h, int m, int s) {
   5         hour = h;
   6         minute = m;
   7         second = s;
   8     }
   9     //这个拷贝构造函数实现的功能与编译器自动声成的相同，可以省略
  10     clock(clock& c) { 
  11          hour = c.hour; 
  12          minute = c.minute;
  13          second = c.second;
  14     }
  15 };
  16 
  17 int main() {
  18     clock c;
  19     clock d(c); //拷贝构造d，其值与c一样。
  20 }