一台电脑上，没有实际的串口设备，只需要安装虚拟串口，再用这段小程序，就可以对电脑VBA程序进行调试了。

这段程序实际上是在一个专门的ExcelVBA文件模块里，模拟外设，与主程序ExcelVBA进行呼应。-A computer, there is no real serial device, only need to install a virtual serial port, and then this little program, you can debug a computer program in VBA. This program is in fact a special ExcelVBA file module, the analog peripherals, with the main program ExcelVBA to echo.