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The X Advantage

From a troubleshooter's perspective, what's so nifty about Mac OS X?

Preemptive multitasking. If you've followed the Windows world in any way, you've probably heard this term. Microsoft has been trumpeting this feature for several years, yet when you ask your average Windows user what it means, they haven't a clue. It means that the operating system can stop and start a job that the computer is performing efficiently to devote the processor's attention to another task. If your Mac is exporting an iMovie to QuickTime, for example, and you launch a spreadsheet and ask the Mac to create a chart, the operating system, through preemptive multitasking, acts as a traffic cop, deciding when the processor should work on the movie and when it should deal with the chart.

The old Mac OS was able to share processes as well by using something called cooperative multitasking. In cooperative multitasking, it was the job of applications to manage a processor's time (rather than the job of the OS). If an application failed to manage that time properly, it could crash and bring the whole shootin' match down with it. Because the operating system is the sole arbiter of a processor's time in preemptive multitasking, this tug of war between applications is a thing of the past.

Protected memory. I mentioned this topic in Chapter 1. For those who've forgotten, protected memory is a scheme whereby applications are allowed to glom onto their own portions of RAM. Because applications don't share memory under Mac OS X, you don't face situations in which a memory error causes the entire Mac to collapse. Instead, memory errors are confined to a single application. Should that applications crash, other applications—and the Mac OS itself—are unaffected.

Dynamic memory allocation. Under Mac OS X, applications can grab as much or as little RAM as they need. If you've spent any significant amount of time with Mac OS 9.2 and earlier, you've undoubtedly seen an error message indicating that such-and-such a program doesn't have enough memory to carry out a particular chore. To skirt this error, you had to quit the application, open its Get Info window, and adjust the amount of RAM assigned to it manually.

This procedure is unnecessary now, thanks to dynamic memory allocation. If an application needs more memory, Mac OS X finds it—either giving up any spare RAM it can find or using virtual memory. (Virtual memory is on all the time in Mac OS X and is much more efficiently implemented than in Mac OS 9.2 and earlier.)

No extensions and control panels. Apple doesn't want anyone dinking around with its pristine operating system, and to protect the OS from such dinking, Apple has made it very difficult for outsiders to patch the OS. Whereas the Mac OS of old could be enhanced by extensions and control panels, Apple has pretty much locked the door with Mac OS X. Users who want to patch Mac OS X must do so in new ways—ways that Apple may very well break with updates to the OS.

From the point of view of users who are looking for an extensible OS and developers who'd like to provide those extensions to their customers, this arrangement isn't so hot. You'll find that many of the utilities you relied on in Mac OS 9.2 and earlier—utilities such as QuicKeys, StuffIt Deluxe, Now Up-to-Date, and Norton Utilities—have fewer features in Mac OS X than they did in the old Mac OS. This situation isn't the fault of the folks who produce these tools; they'd love to give you more capabilities with the Mac OS X version. But to ensure the most stable operating system it can create, Apple has barred their way.

This is good news for troubleshooters, however. No extensions and control panels means no extension conflicts—one of the greatest sources of problems in Mac OS 9.2 and earlier.



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