Exploring the Classic Process

Unlike Cocoa or Carbon applications, Classic applications do not operate as standalone processes. Instead, Classic applications open and run within a single, shared process named TruBlueEnvironment. This single memory space contains Mac OS 9, along with any Classic applications and extensions.

Because Classic applications share a common process and memory space, just as they do in Mac OS 9, they are not protected from each other. If a Classic application crashes, it can crash other applications running in the Classic environment or the Classic environment itself. It cannot crash native Mac OS X applications, because they run in separate, memory-protected spaces.

You should remember that quitting or forcibly quitting the Classic environment shuts down Mac OS 9 and all running Classic applications. If you are having problems quitting a specific Classic application, save your work in other applications before you try the Mac OS X Force Quit command (Command-Option-Escape). You can attempt to force quit the offending application without disturbing the rest of the Classic environment. If the operating system cannot quit the Classic application, it will automatically quit the Classic environment instead.