(MONEY Magazine) – Computer shoppers who buy a Mac are finding something completely different--OS X, Apple's first new operating system since Macs made their debut in 1984. The new system is based on Unix, the heavy-duty OS used by corporate networks. What's the big deal? In a word, stability. With previous versions of the Mac OS, if a single application crashed, you usually had to reboot. Not so with OS X. A feature called protected memory walls off each application so if one blows up, you can force quit and keep working.

Last year, when Apple made a beta version of OS X available, Mac fanatics freaked at the absence of the finder and the drop-down menu in the upper left corner, both of which help with navigation. Apparently, the folks at Apple heard the complaints--both features are back.

Because OS X is so radically different from its predecessor, however, few applications are available. New Macs come with OS X-ready Internet Explorer, QuickTime and AppleWorks (a word processing and graphics program). To run other programs, you have to default to OS 9 (which comes with OS X). For that reason, current Mac users should wait to upgrade (OS X is already on sale for $130) until more OS X applications show up. For an up-to-date list, go to www.guide.apple.com/ussoftware.lasso and click on Built for Mac OS X.

--BRIAN L. CLARK