Portable file names should consist of no more than eight characters, plus an optional extension consisting of a period followed by no more than three characters. Valid characters are uppercase and lowercase letters, digits, the underscore (_), and the hyphen (-). For portability, applications should not assume that file names are case sensitive or case insensitive.

The CfsVolumeInfo class can be used to portably determine file name length and case sensitivity for a specific volume. See Obtaining volume information.

All CFS protocols support the use of DBStrings as file names in locales that support the use of double-byte characters (characters whose values range from 0 to 65535). The limitations on file name length imposed by many platforms are often determined by the number of bytes in the file name rather than the number of characters. Because each character in a DBString can require either one or two bytes of storage, a DBString containing eight characters is not necessarily a valid file name in any given operating system. The use of file names containing double-byte characters is not portable.