How to use Mac OS Classic applications in OS X

From ArticleWorld


When launching OS X, Apple has put a lot of work into ensuring backwards compatibility. OS X includes features that allow you to run older applications designed for older Mac OS systems. This is done through a special subsystem/environment called Classic.

Why would you want to do that? That obviously depends from user to user, but the typical scenario involves and old application, possibly custom-made, that has not been ported to OS X yet, maybe even not being maintained anymore. If you are making the transition to OS X after having used older versions, it will also allow you to use familiar applications, but now that the first OS X version is some years old, chances are you hardly need to do that.

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How to...

  1. First of all, you will need the Classic environment and, if you are using Jaguar or newer versions, a copy of Mac OS 9, since it no longer comes shipped with OS X.
  2. You can install "classic" applications in the usual way, but make sure the Classic service is running. You can start it by starting a Classic application, from the Classic Preferences Panel (System Preferences, Classic) or have it start when you log in. You should extensively check the settings in this panel. If you cannot understand something, contact your system administrator or refer to the OS X documentation.
  3. Before starting a Classic application for the first time, you should check its memory-related settings. To do so, right-click on its icon and choose Get Info. Then, click on the "Memory:" field. Make sure the application has enough memory to run (i.e. at least equal to the "Suggested" size). Increase it if the application is complaining about memory not being enough.
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Notes

Apple has put some work into ensuring that the Classic environment is as closely integrated to OS X as possible. However, this has its limits. Copy and pasting, for example, do work, but:

  • The Classic environment maintains its problems. If a Classic application crashes, it may bring down all other Classic applications. Fortunately, it is enough to restart the Classic environment.
  • The applications still retain their old look'n'fell, even at the level of the top-menu. Classic is not a way of magically turning an old application into an Aqua-enabled one.
  • Many older applications are no longer supported.
  • Mac OS 9 no longer comes boxed with OS X. This means that, in order to use the Classic environment, you will have to purchase it separately, and Apple no longer sells it. You can easily get one from eBay for example, but there is some extra hassle, and it is not supported by Apple either.

All these means that running Classic applications can be unreliable under certain circumstances. Use them only as a last resort.

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