Historical question:

OS 9 has been referred to as a "rolling snowball of features since 1984". But how far does it really go back? The fact that 9.1 still has 68K code seems to indicate that it includes code so old that Apple still doesn't have the source code for it any more (lost in the great flood of 1987?). Clear, OS 9 is based on OS 8, which in turn is basically 7.6 with the Appearance Manager, which was an enhanced version of 7.5, which was an enhanced version of 7.1 (remember the Fonts folder?), which wasn't so different from 7.0. Is that how far back it really goes? 7.0 was very different from 6.0.x, even with MultiFinder.

I'd really appreciate the answer to this if anyone knows.

Aviah

[Costique]

How curious you are!

Yes, some parts of OS 9 have not changed much since System 7, but I think almost all of the OS code has at least gone through bug fixes and minor improvements. The problem with 9.1 is that all human resources at Apple have been busy building OS X for more than a year, and only a small group of developers still work on OS 9. The group is very small and the OS is very large and complicated, so these days they simply don't have enough heads and hands to re-write some components. Nevertheless, OS 9.1 is a large-scale remake of OS 9. They have widened almost every bottleneck, including the complete (according to some sources) re-write of the process manager in PowerPC-native form.
As for lost source code, I doubt this has ever happened to Apple's developers. I presume the problem is the physical size of the project. Furthermore, remember that Mac OS includes hardware drivers, interface management, drawing routines, scripting, printing, networking and so on. I don't believe there are many developers who are equally good at every aspect of a modern OS structure, because the knowledge required for making a single system component is great. The sum range of knowledge required for building a working OS is inconceivable, while an OS 9 team is very small.

------------------
Make no assumptions

[Jsnuff1]

your right, the os hasent really changed since os 6, all os 9 is, is a bunch of upgrades, patches, plugins, etc to os 6, hehe yep OS X is quite and upgrade if you think about it.