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Hub AI
Long filename AI simulator
(@Long filename_simulator)
Hub AI
Long filename AI simulator
(@Long filename_simulator)
Long filename
Long filename (LFN) support is Microsoft's backward-compatible extension of the 8.3 filename (short filename) naming scheme used in MS-DOS. Long filenames can be more descriptive, including longer filename extensions such as .jpeg, .tiff, and .html that are common on other operating systems, rather than specialized shortened names such as .jpg, .tif, or .htm. The standard has been common with File Allocation Table (FAT) filesystems since its first implementation in Windows NT 3.5 of 1994.
To maintain compatibility with older operating systems, Microsoft formulated a method of generating an 8.3 filename from the long filename (for example, Microsoft.txt to MICROS~1.TXT) and associating it with the file.
Microsoft implemented support for LFNs in the FAT filesystem by using hidden directory entries, of the volume label type, to store the longer names; this scheme is known as VFAT, and was chosen for compatibility, as volume labels are generally ignored by programs and operating system (OS) components. Programs running on older OSs could still access the files' short names, while newer, LFN-aware OSs and programs could use the longer ones.
When LFN support was first introduced into a DOS-based operating system in the form of Windows 95, it caused some problems for older programs. For example, a DOS program performing sector-level directory operations while Windows was in DOS mode could destroy long filename information so, by default, sector-level access to hard disks was disallowed in this mode.
Upon booting into plain DOS, the long filenames are not visible unless a VFAT LFN driver is installed. Microsoft did not add LFN support to many of its older programs, including File Manager, the Windows 3.1x (Windows for Workgroups) file manager that was made obsolete by the new operating system shell, Windows Explorer. Windows NT supported LFNs on NTFS file systems starting with the release of NT 3.1, and all of its utilities, including File Manager, were updated to support LFNs. NT 3.5 added FAT LFN support in preparation for Windows 95. However, the Windows 95 version of File Manager came from Windows for Workgroups 3.11.
OS/2 stores LFNs for FAT filesystems in .LONGNAME extended attributes that are incompatible with Microsoft's implementation and only visible to tools supporting OS/2's standard. Many APIs providing access to files by pathname cannot see the new, longer names without a supporting driver.
Because the FAT LFN implementation is layered atop an older, more limited naming system, there are inevitable complications, such as if an attempt is made to create too many files with the same first six letters. Also, one is more likely to encounter issues creating files or folders in the root directory, since FAT12 and FAT16 only allocate space for 512 root directory entries on hard disks. Since long filenames use more than one directory entry, this problem may occur with fewer than 512 files or folders in the root directory. There is space only for 24 long filenames of maximum length (512/(1+20)). This problem does not exist for FAT32 volumes.
The long filename system allows a maximum length of 255 UCS-2 characters including spaces and non-alphanumeric characters (excluding the following characters, which have special meaning within the COMMAND.COM command interpreter or the operating system kernel: \ / : * ? " < > |). This is achieved by chaining up to 20 directory entries of 13 2-byte Unicode characters each. The maximum length of a pathname is 256 characters, which includes all parent directories and the filename. 255-character mixed-case long filename is possible only for files, or folders with no sub-folders, at the root folder of any drive.
Long filename
Long filename (LFN) support is Microsoft's backward-compatible extension of the 8.3 filename (short filename) naming scheme used in MS-DOS. Long filenames can be more descriptive, including longer filename extensions such as .jpeg, .tiff, and .html that are common on other operating systems, rather than specialized shortened names such as .jpg, .tif, or .htm. The standard has been common with File Allocation Table (FAT) filesystems since its first implementation in Windows NT 3.5 of 1994.
To maintain compatibility with older operating systems, Microsoft formulated a method of generating an 8.3 filename from the long filename (for example, Microsoft.txt to MICROS~1.TXT) and associating it with the file.
Microsoft implemented support for LFNs in the FAT filesystem by using hidden directory entries, of the volume label type, to store the longer names; this scheme is known as VFAT, and was chosen for compatibility, as volume labels are generally ignored by programs and operating system (OS) components. Programs running on older OSs could still access the files' short names, while newer, LFN-aware OSs and programs could use the longer ones.
When LFN support was first introduced into a DOS-based operating system in the form of Windows 95, it caused some problems for older programs. For example, a DOS program performing sector-level directory operations while Windows was in DOS mode could destroy long filename information so, by default, sector-level access to hard disks was disallowed in this mode.
Upon booting into plain DOS, the long filenames are not visible unless a VFAT LFN driver is installed. Microsoft did not add LFN support to many of its older programs, including File Manager, the Windows 3.1x (Windows for Workgroups) file manager that was made obsolete by the new operating system shell, Windows Explorer. Windows NT supported LFNs on NTFS file systems starting with the release of NT 3.1, and all of its utilities, including File Manager, were updated to support LFNs. NT 3.5 added FAT LFN support in preparation for Windows 95. However, the Windows 95 version of File Manager came from Windows for Workgroups 3.11.
OS/2 stores LFNs for FAT filesystems in .LONGNAME extended attributes that are incompatible with Microsoft's implementation and only visible to tools supporting OS/2's standard. Many APIs providing access to files by pathname cannot see the new, longer names without a supporting driver.
Because the FAT LFN implementation is layered atop an older, more limited naming system, there are inevitable complications, such as if an attempt is made to create too many files with the same first six letters. Also, one is more likely to encounter issues creating files or folders in the root directory, since FAT12 and FAT16 only allocate space for 512 root directory entries on hard disks. Since long filenames use more than one directory entry, this problem may occur with fewer than 512 files or folders in the root directory. There is space only for 24 long filenames of maximum length (512/(1+20)). This problem does not exist for FAT32 volumes.
The long filename system allows a maximum length of 255 UCS-2 characters including spaces and non-alphanumeric characters (excluding the following characters, which have special meaning within the COMMAND.COM command interpreter or the operating system kernel: \ / : * ? " < > |). This is achieved by chaining up to 20 directory entries of 13 2-byte Unicode characters each. The maximum length of a pathname is 256 characters, which includes all parent directories and the filename. 255-character mixed-case long filename is possible only for files, or folders with no sub-folders, at the root folder of any drive.