AppleScript: The Definitive Guide, 2nd Edition

Classic Scripting Additions

There is a difference between a scripting addition intended to be used with Mac OS 9 or before and a scripting addition intended to be used with Mac OS X. A Mac OS X-type osax will not work on Mac OS 9. A Mac OS 9-type osax will work on Mac OS X only if it has been Carbonized, meaning that internally its Toolbox calls have been linked against CarbonLib . In general, any particular osax file will probably be intended for one system or the other, not both. You may not be able to tell just by looking; if the Show Package Contents menu item appears in the Finder's contextual menu for an osax, it is certainly for Mac OS X, but otherwise you may need to consult the osax's documentation.

Mac OS X on the one hand, and Classic running under Mac OS X on the other, implement AppleScript separately, but the two are compatible and Apple events travel back and forth between them. This raises the question of how the presence of Classic osaxen affects scripts running under Mac OS X. The answer seems to be that any osax terminology in code that targets a Classic application is handled by a Classic osax if possible. You can see this with a term like display dialog, because the dialogs put up by the Mac OS X and Classic versions of this command differ in appearance. So, for example:

set f to "gromit:Applications (Mac OS 9):SimpleText"
tell application f to display dialog "hello" -- clearly the Classicdisplay dialog

On my computer, it is impossible to use English-like terminology ...