On 5/16/07, Jonathan Hutchins hutchins@tarcanfel.org wrote:

For a long time, I've been under the impression, largely from friends who have been running Macintoshes for ages, that OS-X was based on one of the three BSD forks - that essentially it was a *BSD with an Apple window manager/desktop environment, and with the kernel (and other programs) locked to the Trusted Program Module (TPM).

Comments from some of you lately led me to do some research. It appears that, at least on the internet, current documentation agrees that OS-X is based on Openstep, which evolved from NeXTSTEP, which was derived from 4.4 BSD (pre-fork?) and the Mach OS.

It's funny how knowledge like this can evolve on the web. What gets collated, analyzed, and archived becomes the truth. What was known to be true at the time gets forgotten. Mode Emulators become Modulator/Demodulators. Other acronyms drift.

The history of an operating system is not the same as a kernel itself. What you have is mostly correct, but misses a critical juncture in the creation of the OS X kernel. Mach uses several BSD userspace tools, but that doesn't make the kernel BSD derived. Recall that for a long time BSD was a set of software packages that ran on top of someone else's UNIX kernel. Mach was the defining implementation of microkernels. BSD kernels, like Linux kernels, are monolithic in nature.

The internet is confused on the difference between an OS and a kernel, so don't trust the internet. The end result is that OS X is "Based on BSD" in a sense, but not a universal "everything should work after fifteen years of parallel development". So can get X11 apps to compile work, but probably not a driver.

Justin Dugger