Support Long File Names for Files Exposed to Users

[This is preliminary documentation and subject to change.]

Requirement   (Designed for Microsoft® Windows® Logo)

If the application saves files that are exposed to the user, the application must support long file names (LFNs) with all of the following required features:

• Users must be able to enter names of 255 characters including all uppercase and lowercase standard characters, embedded spaces, embedded periods, and so forth.
• Leading and trailing spaces must be stripped by the Save As command. To test this, enter a name with leading and trailing spaces, such as "####This is a test###", retrieve the file, and then make sure the spaces are deleted (the pound sign, #, indicates a spacebar space).
• Question marks anywhere in the file name must prevent the file from being saved. No error message needs to be displayed.
• The following characters must be supported anywhere in the name, including leading and trailing positions, without causing any error conditions:

  +    (plus sign)
  ,    (comma)
  ;    (semicolon)
  =    (equal sign)
  [    (opening square brace)
  ]    (closing square brace)
   

Remarks

Support for leading and trailing periods ( . ) has been dropped from the Logo requirements.

An LFN is 260 characters long, which generally includes:

• 3 bytes for "<driveletter>:\"
• 255 bytes for the file name and extension
• 2 bytes for the null terminator

A Uniform Naming Convention (UNC) path has 2 bytes for "\\" instead of 3 bytes for "<driveletter>:\", and the path may not include an extension (file type).

See Also

See Pretesting UNC and LFN support for a description of pretesting you can do to ensure that your application provides proper UNC and LFN support.