带默认参数的构造函数。又一个有关VC++构造函数重载的源程序，比较适合VC++初学者。以后我上传一系列这种类型的源程序供大家学习之用。-with default parameters of Constructors. One of the Heavy Constructors VC source, more suitable for beginners VC. After I uploaded a series of this type of source for all learning.