I found this little problem circulating via e-mail and social networks, why we get an error while renaming or creating any file/folder with “con” name. Many posts have wrote that “even Bill Gates or the whole Microsoft Team is unable to explain this”. That’s not true. Here is the correct explanation.
The actual reason is that Microsoft MS-DOS reserves certain names for system device drivers. If you try to name a file or folder using one of these names, you will receive the error message, “The specified device driver name is not valid.” So this is not a bug but a programming constraint. This s applicable to nearly all Microsoft DOS versions.
Below is a list of default device driver names which are not permissible as any file/folder name.
| Name | Function |
|---|---|
| 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 |
I have got the list from DOS prompt. To get it type mem/d|more in the DOS prompt. It will show you the full list of device driver names with address and size.
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