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.

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. ;)