Apple needed to show developers that Carbon was going to be a real and valid way forward, not just a temporary stopgap, so they committed to using Carbon for the Mac OS X Finder. The Carbon version of Finder was introduced in Mac OS X Developer Preview 2, before Aqua was revealed; it acted a bit more like NeXT’s, in that it had a single root window (File Viewer) that had a toolbar and the column view, but secondary windows did not. At this stage, Apple didn’t quite know what to do with the systemwide toolbars it had inherited from NEXTSTEP.

[…]

It had taken Apple four years to find the new ‘Mac-like’, and this is the template Mac OS X has followed ever since. Here we are, eighteen years later, and all of the elements of the Mac OS X UI are still recognizable today. So much of what we think of the Mac experience today came from NEXTSTEP, not Mac OS at all. AppKit, toolbars, Services, tooltips, multi-column table views, font & color pickers, the idea of the Dock, application bundles, installer packages, a Home folder, multiple users; you might even be hard-pressed to find a Carbon app in your Applications folder today (and Apple has announced that they won’t even run in the next version of macOS).

Fascinating read by Steve Troughton-Smith on how Apple transitioned from NeXTSTEP to Mac OS X between 1997 and 2001. The purpose of this analysis, of course, isn’t to simply reminisce about the NeXT acquisition but to provide historical context around the meaning of “Mac-like” by remembering what Apple did when the concept of “Mac-like” had to be (re)created from scratch.

Apple is going to be facing a similar transition soon with the launch of UIKit on the Mac; unlike others, I do not believe it means a complete repudiation of whatever “Mac-like” stands for today. The way I see it, it means the idea of “Mac-like” will gradually evolve until it reaches a state that feels comfortable and obvious. I’m excited to see the first steps of this new phase in a couple of weeks.