The system automatically formats a filename correctly if you use the SHGetFileInfo or GetFileTitle function. For more information about these functions, see the documentation included in the Win32 SDK.
Windows provides support for filenames up to 255 characters long. Use the long filename when displaying the name of a file. Avoid displaying the filename extension unless the user chooses the option to display extensions or when the file type is not registered.
Note
The system automatically formats a filename correctly if you use the SHGetFileInfo or GetFileTitle function. For more information about these functions, see the documentation included in the Win32 SDK.
Because the system uses three-letter extensions to describe a file type, do not use extensions to distinguish different forms of the same file type. For example, if your application has a function that automatically backs up a file, name the backup file Backup of filename.ext (using its existing extension) or some reasonable equivalent, not filename.bak. The latter implies a change of the file's type. Similarly, do not use a Windows filename extension unless your file fits the type description.
Long filenames can include any character, except the following.
\ / : * ? < > | "
When your application automatically supplies a filename, use a name that communicates information about its creation. For example, files created by a particular application should use either the application-supplied type name or the short type name as a proposed name — for example, worksheet or document. When that file exists already in the target directory, add a number to the end of the proposed name — for example, Document (2). When adding numbers to the end of a proposed filename, use the first number of an ordinal sequence that does not conflict with an existing name in that directory.
When saving a file, make certain you preserve the creation date of the file. For simple applications that open and save a file, this happens automatically. However, more sophisticated applications may create temporary files, delete the original file, and rename the temporary file to the original filename. In this case, the application needs to copy the creation date as well from the old file to the new, using the standard system functions. Certain system file management functionality may depend on the correct creation date.
When you create a filename, the system automatically creates an MS-DOS filename (alias) for a file. The system displays both the long filename and the MS-DOS filename in the property sheet for the file.
When a file is copied, use the words "Copy of" as part of the generated filename — for example, "Copy of Sample" for a file named "Sample." If the prefix "Copy of" is already assigned to a file, include a number in parentheses — for example, "Copy (2) of Sample". You can apply the same naming scheme to links, except the prefix is "Link to" or "Shortcut to."
It is also important to support UNC paths for identifying the location of files and folders. UNC paths and filenames have the following form.
\\Server\Share\Directory\Filename.ext
Using UNC names enables the user to directly browse the network and open files without having to make explicit network connections.
Wherever possible, display the full name of a file (without the extension). The number of characters you'll be able to display depends somewhat on the font used and the context in which the name is displayed. In any case, supply enough characters such that the user can reasonably distinguish between names. Take into account common prefixes such as "Copy of" or "Shortcut to". If you don't display the full name, indicate that it has been truncated by appending an ellipsis to the end of the name.
You can use an ellipsis to abbreviate path names, in a displayable, but noneditable situation. In this case, include at least the first two entries of the beginning and the end of the path, using ellipses as notation for the names in between, as in the following example.
\\My Server\My Share\...\My Folder\My File
When using an icon to represent a network resource, label the icon with the name of the resource. If you need to show the network context rather than using a UNC path, label the resource using the following format.
Resource Name on Computer Name