按照组件化程序设计方法，用Visual C++编写实现包含IAdd、IStr、IMul三个接口的.dll组件，并利用客户端应用程序完成对各接口的充分测试。-Procedures in accordance with the component-based design method, using Visual C++ prepared containing IAdd, IStr, IMul three interfaces. Dll component and client applicatio