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How Windows Generates 8.3 File Names from Long File Names

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Windows supports long file names up to 255 characters in length. Windows also generates an MS-DOS-compatible (short) file name in 8.3 format to allow MS-DOS-based or 16-bit Windows-based programs to access the files.

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Windows generates short file names from long file names in the following manner:
  • Windows deletes any invalid characters and spaces from the file name. Invalid characters include:
    . " / \ [ ] : ; = ,
  • Because short file names can contain only one period (.), Windows removes additional periods from the file name if valid, non-space characters follow the final period in the file name. For example, Windows generates the short file name
    from the long file name
    This is a really long filename.123.456.789.txt
    Otherwise, Windows ignores the final period and uses the next to the last period. For example, Windows generates the short file name
    from the long file name
    This is a really long filename.123.456.789.
  • Windows truncates the file name, if necessary, to six characters and appends a tilde (~) and a digit. For example, each unique file name created ends with "~1." Duplicate file names end with "~2," "~3," and so on.
  • Windows truncates the file name extension to three characters or less.
  • Windows translates all characters in the file name and extension to uppercase.
Note that if a folder or file name contains a space, but less than eight characters, Windows still creates a short file name. This behavior may cause problems if you attempt to access such a file or folder over a network. To work around this situation, substitute a valid character, such as an underscore (_), for the space. If you do so, Windows does not create a different short file name

For example, "Afile~1.doc" is generated from "A file.doc" because the long file name contains a space.

No short file name is generated from "A_file.doc" because the file name contains less than eight characters and does not contain a space.

The short file name "Alongf~1.txt" is generated from the long file name "A long filename.txt" because the long file name contains more than eight characters.

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Keywords: kbinfo, kbui, KB142982

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Article Info
Article ID : 142982
Revision : 4
Created on : 1/19/2007
Published on : 1/19/2007
Exists online : False
Views : 721