Windows 11 Still Blocks CON, PRN, NUL Filenames

Windows 11 continues to enforce a legacy rule from MS-DOS that restricts certain file names like CON, PRN, AUX, NUL, COM1-9, and LPT1-9. These 'magic file names' are reserved for system devices, tracing back to DOS 1.0. Microsoft developer Raymond Chen explained the rationale in a blog post, noting that these names were used to redirect output directly to devices like printers, without creating files. Despite being outdated, Microsoft retains the restriction to avoid breaking existing batch files and scripts that rely on these names. The rule remains a notable quirk in the modern operating system, often surprising users trying to name files with these reserved terms.