IT giant Microsoft launched on Wednesday the test version of a new generation of Windows operating system, which is designed to run seamlessly on computers and rapidly-growing tablets.

"Windows 8 is a generational change in the Windows operating system," said Windows president Steven Sinofsky.

"It's Windows re-imagined," he added, on the sidelines of the world's biggest mobile fair in Barcelona.

That Microsoft had picked the Mobile World Congress to hold its consumer launch was not coincidental, as the operating system is meant to be its answer to Google's Android platform and Apple, which has dominated a market it ignited with the release of the iPad.

Like its two competitors, Microsoft is going big on the app concept.

Unlike previous generations of Windows, which has a taskbar pulling up a list of software, the latest version is applications-based, with a selection of apps tiled on the startpage.

And the gestures controlling how one selects or moves apps around are those currently common on smartphones, swipes or taps on screens.

"Apps bring to life the operating system. The more apps you have, the better your experience," said Sinofsky.