I want you to copy the contents of this .cpp file and paste it into the header file, then delete this .cpp file. You should get the exact same error (other than say, a difference in line number). If you did not, then obviously you treated this .cpp file as a source file by compiling it when I explicitly told you that it was not a source file, but rather part of a header file. This is also why I suggested that you use a file extension other than .cpp for it.