It's maybe a year before any Windows 8 products come out but Microsoft started pushing what it called its "re-imagined," next-generation operating system to developers this week at its Build conference in California.

Evidently it's trying to freeze the market before its PC empire is utterly chipped away by the upstart Apple and Android.

Microsoft is supposed to be "re-imagining" all its widgetry "from the chipset to the user experience" to run on or through the cloud, an exercise that's supposed to equate to re-imagining Microsoft itself while Windows remains at its core and every business is cloud-optimized and tied together.

Backward-compatible with Windows 7, on which it is based but requiring less memory, Windows 8 is both a leap into OS-disenfranchising cloud services and a tablet catch-up - at least for ARM tablets. It made no firm promises about Intel tablets but reassured the crowd that the highly rated ARM development is keeping pace with its Intel development although Microsoft didn't show it.

Windows 8 is supposed to bring a fully fledged multi-tasking operating system to the tablet along with a battery that can last all day.

One enamored blogger tweeted, "Hello, Windows? This is iPad. You Win."

It's also supposed to run on x86 desktop and laptop PCs and there's a high-end-scaling Windows 8 Server in the offing. Unlike Apple it's all the same stuff.

Windows 8 introduces a new smartphone-like, icon-ditching, tile-based "Metro-style" interface (see below) built for touch, finger-swiping and pinching that can also respond to a mouse and a keyboard (but still supports voice and a stylus).

Behind the tiles are live feeds of, say, photos, e-mails and news.

There's "touch browsing" too complements of Internet Explorer 10 (two version, a Flash-free one for Metro, one for desktops).

Seeking feedback, Microsoft wants ISVs to build full-screen apps to the new interface that lack the usual menus but has yet to confirm there will be a Metro-style Office. It's possible the old familiar Windows desktop will run Office and other traditional programs but that would mean Office doesn't run on ARM and that would mean trouble. Older apps may have to be tweaked or rewritten to run on ARM.

Microsoft handed out 5,000 free development-only Intel i5-based Samsung tablets running Windows 8 at Build and said 500,000 copies of the pre-beta Developer Preview of Win8 were downloaded the first day it was available online. Once loaded on a tablet, it's supposed to offer instant-on; PCs may take a few seconds.

There are three iterations of Windows 8: a 32-bit OS, a 64-bit OS and the 64-bit OS with developer tools. The 64-bit client OS includes Hyper-V.

Programmers can use HTML5, JavaScript, CSS, C#, Visual Basic, .NET, Silverlight, XAML and C++ to build Windows 8 apps. Other languages are reportedly coming although the preference for Metro apps is HTML5 and JavaScript.

Rumor has it Microsoft could have a one-and-only beta ready in time for the Consumer Electronics Show in January, followed by a single Release Candidate and then RTM the stuff.

According to CEO Steve Ballmer, 500 million PCs should be ripe for Win8 upgrades next year. Windows users however are still in the midst of upgrading to Windows 7, which has sold nearly 450 million copies, though sales have been down the last three quarters.

There will of course be an integrated online Windows App store where developers can sell their wares either through direct downloads or through the developers' own sites.

Windows 8 data will be synced across devices and with Microsoft's Skydrive.

Apple is expected to respond.

See http://dev.windows.com for downloads.