C++中extern "C"的设立动机是实现C++与C及其它语言的混合编程。 C++语言支持函数重载，C语言不支持函数重载。函数被C++编译后在库中的名字与C语言的不同。-C++ extern "C" to set up the motivation is to implement a C++ mixed programming with C and other languages. C++ language support function overloading, C language do

使用c++ 实现对类的重载运算符的基本运用-Use heavy-duty exercise c++ realization of the class