con or CON is a reserved file that Windows does not allow you to use and thus being prohibited by Microsoft, this is also because the file is reserved for the computer's console also known as the computer's terminal.
When renaming it: The specified device name is invalid When naming it on Notepad: CON This filename is reserved for use by Windows. Choose another filename and try again.
A shortened term, meaning "Convention". A place where many people with simular intrests gather to show their respects. Such as star trek conventions, anime conventions, and motorcycle conventions.