If you want to write C++ code,
you cannot simply mix C and C++ directly.  To import C code into a C++
project you must prototype them as follows:

extern "C" // c must be a capital C
        {
        extern void Set_320_200();
        extern void Put_Pixel( BYTE Color, WORD x, WORD y );
        }

extern "C" EXPORT YourExportedFunction();
如果没有 extern "C" 修饰，输出函数仅仅能从 C++ 代码中调用。