Sergey Brin, speaking to reporters at Google I/O.

SAN FRANCISCO--Google isn't the only big tech company with two operating systems. But it's the only one with two that take such a different approach.

Android and Chrome OS each got a day to themselves here at Google I/O a conference designed to fire up programmer interest in Google's technology.

With the new Android 3.1, an update to the tablet-centric Honeycomb version, Google yesterday added the ability for people to plug in keyboards, mice, game controllers, and many other USB and Bluetooth devices. In short, it's making the tablet more into a PC, architecturally speaking.

But today, the news was all about Chrome OS, a browser-based operating system that transforms new laptops from Samsung or Acer into vessels for Web applications.

Two days, two philosophies. In one, the device in front of you runs the applications natively, a method that would be old school except that new smartphones are powering an explosion of new programmer interest. The other is the ultimate expression of cloud computing, where a server at the other end of the network is running the show and you just have a powerful remote control.

Google, though, thinks there's room for both. There's no cage-match-to-the-death, two-will-enter-but-only-one-will-come-out-alive approach, Google co-founder Sergey Brin said while talking to reporters today after Google announced the first Chrome OS laptops.

"It's a great dilemma to find ourselves with two fantastic successes on our hands," Brin said, perhaps a little grandly given that the Chromebooks won't even ship until June 15 much less prove themselves a success. "We'd consider ourselves fortunate to have either Android or Chrome OS," he added, implying that instead it has an embarrassment of riches.

Acer Chromebook: Google&39's take on the Netbook

The company's biggest rivals also have two operating systems. Microsoft has Windows and now Windows Phone 7 for mobile devices. Apple has Mac OS X and iOS. Though there are some synergies here and there--perhaps more as ARM-based computers spread and as the mobile OSes grow up--those operating system projects are separate.

But they're still philosophically similar: a device with a processor, input hardware, and an output display is at the center of its own little universe. Google has a much more distributed view of the world.

Of course, even with Android, the cloud is important. It's intended to be a conduit to Gmail, Google Docs, and other Net-based services. Android is intended to accelerate the mobile-computing revolution, a job it's doing well (with Apple leading much of the charge), so part of its purpose is to link to a server.

With Chrome OS, the cloud isn't just important, it's almost all there is. You can use local files--view PDFs, play music, watch videos--but those features are more necessary evils than the heart of the experience. Google makes sure that when you plug a camera into the USB port, you can quickly transfer the photos to Picasa Web Albums.

Sundar Pichai, senior vice president of Chrome, argues that Android and Chrome OS provide "different, unique computing experiences."

"It's a very different model," Pichai said, pointing out that each reporter in the press Q&A had both a phone and a laptop. "We want to provide that choice to users and developers alike."

He has a point. Mobile phones don't have enough processing power to handle the highly abstracted mechanisms browsers provide for fancy graphics. And Web sites and Web apps often work poorly if at all on smartphones' small touch screens. So there's a big role for native apps are more.

But things are quite as simple as saying Google offers different tools for different circumstances. Android and Chrome OS are headed to similar hardware realms.

Take Google TV. With an Atom processor, a big screen, and a reliable home broadband connection, why not put Chrome OS on it And what's the best OS for a tablet If you're a hardware partner, which of Google's priorities should be yours

Another complication: app stores. Do people who've bought an Android game in the Android market have to re-purchase it through the Chrome Web Store Angry Birds is available in both, and it's safe to expect others to cross the divide.

Finally, there's the developer issue. Google must evangelize two separate, incompatible ecosystems. It has to produce development tools for each, too.

Overall, though, if any company can hold two such different ideas in its head at the same time, it's Google. The company loves programmers, and judging by how packed to the gills Google I/O is, a fair number of them love Google. And regardless of the fortunes of Chrome OS and Android, programmers will be writing for both types of operating systems.

That's because Web programming is a major force today, regardless of Chrome OS, and mobile apps are a major force today, regardless of Android. Both methods will thrive in coming years. Even if supporting both muddies the waters for Google's priorities and messaging, they're not mutually exclusive.