Apple's new operating system turns up heat on Microsoft.

Byline: Dawn C. Chmielewski

Apr. 25--The cat's out of the bag.

Tiger, the latest version of Apple Computer's Mac OS X operating system, debuts Friday. This is hardly news to the Mac faithful, who've been alerted through daily e-mail reminders and a running countdown on Apple's Web site to the day Tiger is "unleashed."

The folks in Redmond are bracing as well. Tiger, Apple's fifth major operating system upgrade in four years, keeps the competitive pressure on Microsoft, which is at least a year away from introducing the successor to Windows XP, dubbed "Longhorn."

It's not that Tiger is about to eat Longhorn for lunch -- after all, Microsoft Windows runs 94 percent of the world's personal computers. Rather, Apple's history of operating system innovations sets the standard for Microsoft to imitate or exceed.

What makes Tiger innovative, rather than merely iterative, is that it breaks down the barriers between the self-contained computer and the Internet. It is the first operating system to incorporate and expand upon the intensive hard-drive search popularized by Google. It also fetches the kind of up-to-the-minute stock, weather and flight information typically found …