In Windows 11, certain names such as CON, PRN, AUX, and NUL are reserved as they correspond to specific devices, preventing users from naming folders with these terms. These reserved names date back to DOS 1.0, where folders did not exist. The names have specific functions: CON refers to the console, PRN to the printer, AUX to an auxiliary device, and NUL to a null device that discards output. Attempts to rename a folder to any of these names result in an error message indicating the device name is invalid. Adding extensions to these names does not bypass the restriction, as names like NUL.txt are still treated as equivalent to NUL. Despite some changes in Windows 11, the prohibition against using these reserved names for files or folders remains in place due to legacy compatibility concerns.