Programs that recognize long file names must indicate this by including the NEWFILES statement in their module definition file. This statement directs the linker to set a bit in the executable file header. It indicates that the module supports long file names. This bit is meaningless in a DOS Session and on versions of the OS/2 operating system prior to Version 1.2. Programs written for OS/2 Version 1.2 (and all later versions) installable file systems should set this bit. Bound programs that have this bit set can see files with long file names in OS/2 mode, but only files with 8.3 file name format in DOS Sessions.

This bit has meaning when attached to program modules, not when attached to DLLs. Whether the program recognizes long file names format is entirely dependent on the value of its NEWFILES bit and the effect of the bit extends into any calls to DLLs. In order to be compatible with all OS/2 file systems, dynamic link libraries must not create internal temporary files or directories that do not comply with 8.3 file naming conventions. In addition, dynamic link libraries cannot return long file names to an application. (The caller might be running on a file system that only supports 8.3 file names and use the returned name to create a file.)

OS/2 applications which do not recognize long file names can run with some restrictions. For these programs, long names (including device names) are filtered according to the following rules:

• Any name not representable in the 8.3 file name format is not returned from DosFindFirst or DosFindNext. This is because the application's buffers are unlikely to be large enough to handle longer names.

• Any long file name passed to the file system functions listed below are rejected in exactly the same way as under previous versions of the OS/2 operating system. It is not acceptable to create and manipulate a name that you cannot find.

  DosOpen
  DosDelete
  DosMove
  DosQueryPathInfo
  DosSetPathInfo
  DosCreateDir
  DosDeleteDir
  DosFindFirst
  DosFindNext
  DosQueryFSAttach
  DosFSAttach
  DosCopy
  DosSearchPath

  
  Long file names can be passed to DosSetCurrentDir and DosQueryCurrrentDir so that all programs can use all directories.
  
  Long names used with non-file system functions (for example, DosCreateSem) are not filtered.

  For files located on file devices managed by the OS/2 FAT file system, long file names are handled differently in OS/2 mode than in DOS mode. In OS/2 mode, the long file name is considered an error. In DOS mode, the name is truncated and is not an error. The DOS mode treatment of file name formats provides compatibility with the PC-DOS environment for applications originally written for PC-DOS. However, if you are writing a family application to run under both the OS/2 operating system and the PC-DOS environment, your application must allow for this difference in operating environments.

  Because long file names can be input to applications through program command lines, dialog boxes, or function calls, applications must provide their users with rules for how to enter file names. File Names in User Input provides some general guidelines in this matter, that are applicable to both long file names and 8.3 file names.

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