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[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Logical Structures and File Systems | New Technology File System (NTFS) | NTFS Directories and Files ]

NTFS File Naming

Microsoft's early operating systems were very inflexible when it came to naming files. The DOS convention of eight characters for the file name and three characters for the file extension--the so-called "8.3 standard"--was very restrictive. Compared to the naming abilities of competitors such as UNIX and the Apple Macintosh, 8.3 naming was simply unacceptable. To solve this problem, when NTFS was created, Microsoft gave it greatly expanded the file naming capabilities.

The following are the characteristics of regular file names (and directory names as well) in the NTFS file system:

  • Length: Regular file names can be up to 255 characters in NTFS.
  • Case: Mixed case is allowed in NTFS file names, and NTFS will preserve the mixed case, but references to file names are case-insensitive. An example will make this much more clear. :^) Suppose you name a file "4Q Results.doc" on an NTFS volume. When you list the directory containing this file, you will see "4Q Results.doc". However, you can refer to that file by both the name you gave, as well as "4q results.doc", "4q ReSulTS.dOc", and so on.
  • Characters: Names can contain any characters, including spaces, except the following (which are reserved because they are generally used as file name or operating system delimiters or operators): ? " / \ < > * | :
  • Unicode Storage: All NTFS file names are stored in a format called Unicode. Recall that conventional storage for characters in computers is based on the ASCII character set, which uses one byte (actually, 7 bits) to represent the hundred or so "regular" characters used in Western languages. However, a single byte can only hold a couple of hundred different values, which is insufficient for the needs of many languages, especially Asian ones. Unicode is an international, 16-bit character representation format that allow for thousands of different characters to be stored. Unicode is supported throughout NTFS.

Tip: For more information about Unicode, see this web site.

You may recall that when Windows 95's  VFAT file system introduced long file names to Microsoft's consumer operating systems, it provided for an aliasing feature. The file system automatically creates a short file name ("8.3") alias of all long file names, for use by older software written before long file names were introduced. NTFS does something very similar. It also creates a short file name alias for all long file names, for compatibility with older software. (If the file name given to the file or directory is short enough to fit within the "8.3", no alias is created, since it is not needed). It's important to realize, however, that the similarities between VFAT and NTFS long file names are mostly superficial. Unlike the VFAT file system's implementation of long file names, NTFS's implementation is not a kludge added after the fact. NTFS was designed from the ground up to allow for long file names.

File names are stored in the file name attribute for every file (or directory), in the Master File Table. (No big surprise there!) In fact, NTFS supports the existence of multiple file name attributes within each file's MFT record. One of these is used for the regular name of the file, and if a short MS-DOS alias file name is created, it goes in a second file name attribute. Further, NTFS supports the creation of hard links as part of its POSIX compliance. Hard links represent multiple names for a single file, in different directories. These links are each stored in separate file name attributes. (This is a limited implementation of the very flexible naming system used in UNIX file systems.)

Next: NTFS File Attributes

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