Create CON, AUX, NUL folder and files in a click in Windows

Most of you may be aware that MS-DOS Device Driver names cannot be used as file names in Windows. As a result, we are unable to name folders as con, aux, nul, etc.

Microsoft MS-DOS had reserved these names for these system device drivers.

  • CON : Keyboard and display
  • PRN : System list device, usually a parallel port
  • AUX : Auxiliary device, usually a serial port
  • CLOCK$ : System real-time clock
  • NUL: Bit-bucket device
  • A:-Z: : Drive letters
  • COM1 : First serial communications port
  • LPT1 : First parallel printer port
  • LPT2 : Second parallel printer port
  • LPT3 : Third parallel printer port
  • COM2 : Second serial communications port
  • COM3 : Third serial communications port
  • COM4 : Fourth serial communications port

Try to create a file or folder with these names on your Windows desktop and see what happens.

CON, AUX, NUL folder

Even today if you try to name a folder using one of these reserved names, you will receive the following error message: The specified device name is invalid.

These restrictions still exist in the NT-based Windows, possibly the reason being to allow compatibility for running 16-bit programs and for command-line based programs. The complete Windows Naming Files, Paths, Namespaces, Conventions can be found here.

Create CON, AUX, NUL folder

While you can use Linux or MS-DOS commands to create the folder names such as “con”, I came across this app Concu which claims to let you create and delete folders with restricted names, in a click. It’s a CNET link so remember to click on the Direct Download Link.

Why does this program exist? Just to make a point that it can be done using a tool, that’s all!

I know, I know this is real old stuff, but this is for those who may not be knowing about it. 😉

Posted by on , in Category Windows with Tags
Anand Khanse is the Admin of, a 10-year Microsoft MVP Awardee in Windows (2006-16) & a Windows Insider MVP. Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.


  1. Shankar

    I am not a computer expert, but my question is can this program be useful to use DOS applications-Games,etc.

  2. Deepak_kapoorjob3

    you can create that by inserting alt+255con

  3. BobBobson

    No. That is not “con”, that is “_con” where the underscore is a placeholder for the character 0x255 which in some codepages looks like a space, in others, looks like ÿ, and so on. That is NOT the same thing as just plain “con”.

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