UNIX-y feel?
Not really. You have to *go look for* the UNIX stuff. Your portal is Terminal ( located at /Applications/Utilities/Terminal.app). Terminal is just that... it's like xterm in *nix.
But, Mac OS X is a strange animal, it's both "a UNIX" and "not a UNIX".
Darwin, the core bits of the OS are built from the Mach kernel, using a BSD subsystem. All the utilities are from BSD code.
You never see any of the UNIX, because, honestly, it has no bearing on what you're doing. The BSD subsystem provides kernel-level drivers for hardware and devices. User-level access is provided through the NeXTStep layers that ride atop UNIX.
If you know anything at all about NeXTStep or OpenStep, or Rhapsody, then you can bank on it that OS X is 99% the same.
The parts that make it OS X, though, are all high-level Objective-C classes and frameworks that ride atop Darwin. All of those parts could easily run on any OS. Be it Linux, NT, Be OS, or even Mac OS 9.2.2.
Native OS X apps use one of two APIs, Cocoa, which is an updated version of YellowBox (the NeXTStep/OpenStep API), and Carbon, which is an overhaul of the classic Mac OS API. Carbon can run natively on both OS 9 and OS X.
UNIX apps are much lower level, and are kinda primitive in comparison. UNIX apps cannot access Quartz (the display layer) or use Aqua (the UI and appearance). OS X doesn't include X11. It can be installed from Disc 3 of the OS X 10.3 CD, or downloaded from Apple, but I think it only runs on 10.3 now.
[ January 15, 2004: Message edited by: Jimmy don't give a shit about MS ]