With the exception of the OpenFile function, all of the functions in Windows version 3. x that require the application to pass in a filename (such as LoadLibrary, WinExec, _lopen, and _lcreate) have been updated to support long filenames. For compatibility reasons, functions that return filenames should return only aliases (8.3 filenames) to 16-bit Windows – based applications marked less than 4.0.
MS-DOS – based applications generally use the Interrupt 21h functions. Except for Extended Open/Create (Interrupt 21h Function 6Ch), the older Interrupt 21h functions have not changed in Windows 95. Extended Open/Create has been enhanced in Windows 95 to make use of the last access date for a file. To support long filenames, Windows 95 provides many new Interrupt 21h functions. Any MS-DOS – based application that will use long filenames must be updated to support the new functions. For information about the long filename Interrupt 21h functions, see Long Filenames
Windows 95 supports the new Interrupt 21h long filename functions on as many file systems as possible. On file systems, such as MSCDEX, Flash, and real-mode network redirectors, that do not support long filenames, the system automatically translates the newer Interrupt 21h calls to the appropriate older Interrupt 21h calls, as long as the filename passed as a parameter is a valid alias (8.3 filename). Applications may use Get Volume Information (Interrupt 21h Function 71A0h) to retrieve information on the capabilities of the underlying file system.