Google has taken a big step in trying to redefine the laptop, making it purely Web-centric, untethered to the Windows past.

Chromebooks are, in a way, tablets with keyboards, as Hugo Barra, director Android Product Management at Google, said today at Google's I/O developers conference, streamed here. That's a key point of departure from the traditional small Windows laptops, aka, Netbooks.

"Attributes that make phones and tablets great...we're bringing this to notebooks," he said.

Those attributes include Cloud-based apps, extreme portability, built-in 3G connectivity, instant-on, and all-day battery life--all hallmarks of tablets like Apple's iPad and Motorola's Xoom.

Acer&39's Chromebook starts at $349 and 2.95 pounds. It runs Google&39's Chrome OS on top of an Intel dual-core N570 Atom processor.

The similarly-sized Netbook, on the other hand, has been, since its debut in 2007, essentially a conventional Windows laptop, just smaller. Google's focus on instant-on, instant Web connection is a seemingly trivial feature but a key difference between traditional laptops and so-called post-PC devices, like the smartphone and tablet.

"Every Chromebook is instant turn on. Every time you boot up, you're up and running within eight seconds," Barra said.

In this respect, Google may succeed where Qualcomm's "smartbook" failed. That laptop actually aspired to many of the same things but never became a viable commercial product.

But the Chromebook's novelty can potentially be a weakness. Particularly for businesses and educators still tied to Windows. Google is trying to address that with Web-based management features. "Seamless updates directly from Google keep the operating system and software fresh, eliminating the need to manually patch systems," Google states on its Chromebook page. "And since only minimal data is stored on the device, you don't need to do tedious backups or migrate data when changing hardware," according to Google.

Google is also employing security features such as secure tabbed browsing (called "sandboxing"), user data encryption, and verified boot.

Both Acer and Samsung will release Chromebooks June 15 running the Chrome OS on top of Intel's latest dual-core Atom N570 processor. And the N570 is a step up from the single-core Atom that powered the prototype CR-48 Chromebook, distributed to journalists, among others, in December.

Chromebook features:

Amazon is already listing Chromebooks here.