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                                                181
SECTION 3.10                                                                File Specifications



  without a drive by making the first component empty. (Empty components are
  ignored by other platforms.)
• For Mac OS, all components are separated by colons ( : ).
• For UNIX, all components are separated by slashes ( / ). An initial slash, if
  present, is preserved.

Strings used to specify a file name are interpreted in the standard encoding for
the platform on which the document is being viewed. Table 3.40 shows examples
of file specifications on the most common platforms.

                      TABLE 3.40 Examples of file specifications
SYSTEM          SYSTEM-DEPENDENT PATHS                 WRITTEN FORM

DOS             \ pdfdocs \ spec . pdf ( no drive )    ( / / pdfdocs / spec . pdf )
                 r : \ pdfdocs \ spec . pdf            ( / r / pdfdocs / spec . pdf )
                pclib / eng : \ pdfdocs \ spec . pdf    ( / pclib / eng / pdfdocs / spec . pdf )

Mac OS          Mac HD : PDFDocs : spec . pdf          ( /Mac HD/ PDFDocs/ spec . pdf )

UNIX            / user / fred / pdfdocs / spec . pdf   ( / user / fred / pdfdocs / spec . pdf )
                 pdfdocs / spec . pdf ( relative )      ( pdfdocs / spec . pdf )


When creating documents that are to be viewed on multiple platforms, care must
be taken to ensure file name compatibility. Only a subset of the U.S. ASCII
character set should be used in file specifications: the uppercase alphabetic
characters (A–Z), the numeric characters (0–9), and the underscore ( _ ). The
period ( . ) has special meaning in DOS and Windows file names, and as the first
character in a Mac OS pathname. In file specifications, the period should be used
only to separate a base file name from a file extension.

Some file systems are case-insensitive, and names within a directory should
remain distinguishable if lowercase letters are changed to uppercase or vice
versa. On DOS and Windows 3.1 systems and on some CD-ROM file systems,
file names are limited to 8 characters plus a 3-character extension. File system
software typically converts long names to short names by retaining the first 6 or
7 characters of the file name and the first 3 characters after the last period, if any.
Since characters beyond the sixth or seventh are often converted to other values
unrelated to the original value, file names must be distinguishable from the first
6 characters.

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