Naming a File or Directory

Files and directories on both Windows file systems, NTFS and FAT, can be up to 255 characters long and can contain spaces, multiple periods, and special characters that are forbidden in MS-DOS file names.

When you create a long name, Windows automatically creates a shorter, MS-DOS-style name. This allows MS-DOS-based computers and applications that do not support long file names to access the directory or file. However, if you save a file using an application that does not support long file names, the long file name will be lost and the file will keep only a short name.

All of the following file naming rules apply to both NTFS and FAT:

Names can be up to 255 characters long including extensions. Separate the extension from the name with a period.
Names preserve case, but are not case sensitive. Windows retains your use of uppercase and lowercase letters; however, Windows does not distinguish filenames by their case.
Names can contain any uppercase or lowercase characters except the following: ? " / \ < > * | :