In all versions of Windows, we are unable to rename a file or a folder name as CON without third-party file renaming software. Trying to do this in Windows 7 results in an error:
The specified device name is invalid.
Trying to save a file as con.txt in Notepad leads to a similar error:
This file name is reserved for use by Windows.
Choose another name and try again.
Why can't we name a file or folder CON in Windows?
"con" is the name of a system I/O device, the console.
And a couple others, I think.
In the old days it was common in DOS to create a file (and I still do this occasionally) with:
C:\>copy con foo.txt
I'm typing some text here.
^Z
1 file(s) copied.
C:\>
I gave this answer to a duplicate, and thought I'd post it here for your reference:
As previously stated. It's a reserved word from back in MS-DOS, for the CONsole device (as far as I can remember). But, you can force Windows/dos to create the folder for you. For devices, it uses the format \\.\[RESERVED_WORD] to access the "file" (these devices used files for communication). To force Windows to create your folder, instead of doing mkdir [RESERVED_WORD], do the following:
mkdir \\.\[absolute path to folder of choice, including drive letter]\[RESERVED_WORD]
For example, to create CON folder on my desktop,
mkdir \\.\C:\Users\me\Desktop\CON
To delete the folder, you have to reference it the same way, or else it won't work.
rmdir \\.\C:\Users\me\Desktop\CON
My advice though is to just use a different name. It would be very difficult to always refer to it via its absolute path, especially if you are developing an app you plan on deploying.
This is because it is used to represent the "internal devices". However, you can create this folder using the following command in a command prompt:
C:\>md \\.\e:\con
This folder can't be deleted via right click, delete. You have to use the following command (again in a command prompt):
C:\>rd \\.\e:\con
You can rename it without using any special software, just the command prompt:
For example:
C:\>echo Test > \\?\C:\con
C:\>type \\?\C:\con
Test
C:\>rename \\?\C:\con test.txt
C:\>type test.txt
Test
After \\?\ the full path should be specified.
Extending Pablo Santa Cruz's answer, here is the full list of keywords that are used by Windows internally and are reserved. As with all Windows filenames, the following are case insensitive.
Source: The specified device name is invalid at Microsoft Docs.
You can use _con instead.
As mentioned, you can create and manipulate files and folders with reserved names on the command line by using a device or filename namespace such as \\.\C:\NUL, but look at what happens when you try to access such a file or folder through Windows Explorer:
Any access to an object with a reserved device name is treated as referring to the device specified by that name, unless you use the aforementioned namespace workaround. These errors occur because Windows is attempting to operate on them as if they were normal folders, but you can't open a device named NUL, CON, or otherwise as a folder—hence the Incorrect function error (which is similar to the Inappropriate ioctl for device error on Linux).
copy con is an archaic (MS-DOS) method of creating a text file. For example:
copy con output.txt
So it is a reserved word and cannot be used as a folder name in Windows.
