The Classic Environment and Boot Camp
The Classic environment and Boot Camp are very different technologies, but they serve (or, in the case of Classic, served) the same essential purpose--provide the technological safety net and the psychological peace of mind that allowed millions of people to make the switch to Mac OS X.
For most "classic" Mac users, the transition from Mac OS 9 to Mac OS X went far more smoothly than even the most optimistic among us expected. But it never would have been so had it not been for the Classic environment, a hardware-abstraction layer that let users run OS 9 applications within Mac OS X, side-by-side with native OS X software. Without the Classic environment, upgrading to Mac OS X would have meant either doing without your favorite software until it was updated for the new OS, or dumping all your existing software and starting over--a prospect only slightly more appealing than simply giving in and switching to Windows. The Classic environment wasn't perfect--some OS 9 apps acted a bit quirky when run within Classic, and a few didn't function at all--but for the most part it worked well and worked invisibly, tiding many a Mac user over until one day, as if by magic, it was no longer needed.
Boot Camp has fulfilled a similar role for Windows users. Since its debut (in beta form in early 2006, with an official release in late 2007), Boot Camp has offered Windows users the assurance that if they decide to switch to the Mac, they can still run all their Windows software--or, in the worst-case scenario, that if they end up hating OS X, they can permanently boot into Windows and just use their Mac as a fully supported Windows PC. (The latter option makes Boot Camp more compelling for many Windows switchers than virtualization solutions such as Fusion and Parallels.) Of course, after making the switch, many Windows users end up finding suitable--or superior--OS X replacements for their favorite software, and become full-time Mac OS X users. But without Boot Camp, they never would have been in the position to not boot into Windows.--DAN FRAKES
Apple's developer tools are probably the top candidate for the title of "most important technology that the majority of Mac users will never touch." Back in the heady days of the classic Mac OS, developers who wanted to write software for the Mac were dependent on integrated development environments (IDEs) such as Metrowerks's CodeWarrior. When OS X rolled around, Apple seemed to have realized that in order for its future platform to thrive, it couldn't afford to have the means for creating great software controlled by someone else. Hence, the introduction of Apple's own developer tools alongside Mac OS X. Included in the package was an IDE--Project Builder--that was a tweaked version of the IDE that came with NeXT, the OS whose acquisition laid much of the foundation for OS X. In 2003, Project Builder became the now familiar Xcode.
Controlling the tools used to build software gave Apple a huge edge: the company could make sure developers were able to take advantage of the new, compelling features that Apple rolled out in each successive OS X update. The company positioned Xcode and the other development tools as an investment in the future of its platform, distributing them for free along with every copy of OS X--that was a marked contrast to IDEs like CodeWarrior, which often ran hundreds of dollars. While Xcode may not be a technology that most Mac users are intimately familiar with, it's the software that makes possible pretty much every application you use on your Mac, and that's no small deal.--DAN MOREN
Unix underpinnings and a modern core
The Unix underpinnings provided Mac OS X with something long lacking in the Mac OS: stability and performance. Prior versions of the Mac OS lacked protected memory, which meant that when one app crashed, the Mac itself usually crashed. Multitasking performance was also far from stellar, as the OS was written without multitasking in mind.
Mac OS X changed all that, thanks to its modern core and Unix foundation layer. Typical users may never directly see the Unix side of Mac OS X, nor even care that it's there...but every time they use their Mac, they benefit from that core: multiple programs run simultaneously, all playing nicely with each other; when a program crashes, only that program crashes. With the advent of Mac OS X, multi-daily reboots became a thing of the past, and were soon measured in days or weeks. Thanks to this solid core, Mac OS X and its programs are stable, responsive, and work well with one another.--ROB GRIFFITHS
As displays got larger through the years and Mac OS X’s multitasking features became even more robust, the desire to keep more windows and applications running concurrently could often lead to “window-itis”—the condition of getting buried under one’s virtual workspace. When Apple released Mac OS X 10.3 in 2003, it showcased its unique knack for tackling usability problems like this with the introduction of Exposé.
Exposé was arguably the first significant attempt by a major OS maker to improve window management since Windows 95 (or perhaps WindowShade in System 8). When Command-Tab and repeatedly hiding or minimizing waves of windows were no longer enough, Exposé offered a refreshing bird’s-eye view of all the applications, or just multiple windows in a single application, that were currently open, as well as the files on your desktop. The feature debuted with just three modes, accessible by keyboard shortcuts and mouse gestures: All Windows, Application Windows, and Show Desktop. For some, Exposé was largely a novelty or a fun trick to show friends why the Mac is cool. For others, Exposé was a window management game changer, a new lease on being productive that helped proved why the Mac is great.
Apple eventually added multi-touch trackpad gestures in Leopard, as well as some other minor perks in Snow Leopard, to make Exposé more accessible. But the feature has largely remained unchanged—though useful as ever—since its introduction in 2003.—DAVID CHARTIER