I have received the following mail so many times including an sms about it on my mobile. This is what it says,

“An Indian discovered that nobody can create a FOLDER anywhere on the computer which can be named as CON. This is something pretty cool…and unbelievable… At Microsoft the whole Team couldn’t answer why this happened!
TRY IT NOW, IT WILL NOT CREATE CON FOLDER.”

Here is the justification why a folder named “CON” cannot be created. Windows has been inherited from MS DOS which again was inherited from an operating system called QDOS (Quick and Dirty Operating System). Till today all the MS operating systems including the servers still have the kernel shell functions of MS DOS. DOS was a text console based OS. CON is a reserved word which meant console or the visual display unit. So anything when redirected to CON went to the display device which is the monitor. Since it is a reserved word DOS restricted that word to be used elsewhere like creating file named CON or creating a directory named CON. Here is a sample test. Go to DOS prompt. Type this command,

c:\> copy con Hello

Keep entering text as many lines as you want and when you are done press (Ctrl key + Z). Give Dir command and you can see that a file named Hello was created. What that command essentially does is create a file whatever that is typed and displayed onto the console. Lets try another example. Try this command

c:\> copy con

Enter some text and press the enter key. What do you see? DOS will echo whatever you have typed. press Ctrl + Z to come out of it.
There is no other reason other than CON being a reserved word and to retain the functionality of DOS shell, that Windows does not allow a folder to be created with the name CON. So you must be wondering if there are any other reserved words and you cannot create a folder with that word. Here is the list. If you create these folders in windows explorer it will create them but internally it is represented differently. To really test it is not possible, go to DOS prompt and try creating a directory (using mkdir command) with the below names.

PRN - refers printer
NIL - refers void (DOS will fool you that it created a directory but it wont be there)
AUX - refers to the auxilary device
COM1 - COM 1 port
COM2 - COM 2 port
COM3 - COM 3 port
COM4 - COM 4 port
LPT1 - LPT 1 port
LPT2 - LPT 2 port
LPT3 - LPT 3 port
And this is only in DOS and Windows systems, it will work pretty cool on a Unix system. Sometimes we get so excited by such mails that we are focused only in forwarding them, rather than trying to find out if the claim is valid.