类继承， 子类初始化调用父类构造函数

  如下， 在子类 engineer 的构造函数后面跟冒号调用了父类 employee 的构造函数。
  (C++ Programming Made Simple 2ndE, Chapter 9, Page 231)


class employee
{
public:
    employee(int id, char *name);
 };

class engineer : public employee
{
public:
    engineer(int id, char *name, char *department);
}

engineer::engineer(int id, char *name, char *department) : employee(id, name)
{
    //....
}