File Systems

Files created or renamed on FAT volumes use attribute bits to support LFNs in a way that does not interfere with how MS-DOS gains access to the volume.

Whenever you create a file with an LFN, Windows 2000 creates a conventional 8.3 name for the file and one or more secondary folder entries for the file, one for each set of 13 characters in the LFN. Each secondary folder entry stores a corresponding part of the LFN in Unicode. MS-DOS accesses the file by using the conventional 8.3 file name contained in the folder entry for the file.

Windows 2000 marks the secondary folder entries as part of an LFN by setting the volume ID, read-only, system, and hidden attribute bits. MS-DOS generally ignores folder entries with all these attribute bits set, so these entries are invisible to it.

Figure 17.5 shows all of the folder entries for the file Thequi~1.fox, which has a long name of The quick brown.fox. The long name is in Unicode, so each character in the name uses 2 bytes in the folder entry. The attribute field for the long-name entries has the value 0x0F. The attribute field for the short name has the value 0x20.

Figure 17.5 LFN on a FAT Volume

Note

Windows NT and Windows 2000 do not use the same algorithm to create long and short file names as Windows 95 and Windows 98. However, on computers that use a multiple-boot process to start these operating systems, files that you create when running one operating system can be accessed when running another.

For more information about how Windows 2000 creates short file names, see Using Long File Names later in this chapter.

By default, Windows 2000 supports LFNs on FAT volumes. You can prevent a FAT file system from creating LFNs by setting the value of the Win31FileSystem registry entry (in subkey HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\FileSystem) to 1. This value prevents Windows 2000 from creating new LFNs on all FAT volumes, but it does not affect existing LFNs.

Warning

Do not use a registry editor to edit the registry directly unless you have no alternative. The registry editors bypass the standard safeguards provided by administrative tools. These safeguards prevent you from entering conflicting settings or settings that are likely to degrade performance or damage your system. Editing the registry directly can have serious, unexpected consequences that can prevent the system from starting and require that you reinstall Windows 2000. To configure or customize Windows 2000, use the programs in Control Panel or Microsoft Management Console (MMC) whenever possible.