The information in this article applies to:
- Microsoft Windows NT operating system, version 3.1
- Microsoft Windows NT Advanced Server, version 3.1
The Windows NT filesystem (NTFS) support filenames up to 255
characters long. In most cases, NTFS also generates an MS-DOS
compatible filename in 8.3 (filename.extension) format that allows an
MS-DOS-based or 16-bit Windows-based application to access the same
files.
NTFS translates a long filename to an 8.3 filename in the following
manner:
- NTFS deletes any illegal characters from the long filename and
removes any spaces. The resulting filename must be a letter or a
number and it must not contain the following illegal characters:
. " / \ [ ] : ; = ,
If the filename contains any of these characters, unexpected
results may occur. The resulting filename cannot contain any
spaces.
- Because an 8.3 filename can contain only one period (.), NTFS
removes additional periods from the filename if valid, non-space
characters follow the final period (see Example 1 below).
Otherwise, NTFS ignores the final period and uses the second to
last period (see Example 2 below).
Example 1: This is a really long filename.123.456.789.txt
converts to THISIS~1.TXT
Example 2: This is a really long filename.123.456.789.
converts to THISIS1.789
- NTFS truncates the filename, if necessary, to six characters and
appends a tilde (~) and a digit. For example, each unique filename
created ends with "~1". Duplicate filenames end with "~2", "~3",
and so on.
- NTFS truncates the filename extension to three or fewer characters.
- NTFS translates all characters in the filename and extension to
uppercase. (File Manager displays filenames in lowercase.)
An exception to the rules above occurs when the NTFS directory name or
filename contains space and fewer than eight characters. In this case,
NTFS does not create an 8.3 filename. This may cause problems if you
attempt to access the file or directory through a network. To work
around this situation, substitute an illegal character, such as a "[",
for the space and NTFS will create a legal 8.3 filename. Even though this
behavior seems inconsistent, it maintains compatibility with MS-DOS.
In MS-DOS, a space is considered an illegal character and causes similar
problems when it is used in that environment.
The following examples demonstrate how NTFS applies these rules:
a file.doc
This is not converted because the filename has fewer than 8
characters and contains a space.
a[file.doc
This is converted to A_FILE~1.DOC because the filename contains
illegal characters.
A Long Filename.TXT
This is converted to ALONGF~1.TXT because the filename contains
more than 8 characters.