Seattle-based US software giant Microsoft on Wednesday staged a public test release of its Windows 8 operating system at the Mobile World Congress in Barcelona, Spain.

The company aims to start selling the final version in the fall of this year and claims that Windows 8 will be the most important product from the flagship Windows division in at least a decade.

Windows 8 will have some obvious differences from its predecessors. It won't have a "Start" menu; all applications are spread across a mosaic of tiles resembling road signs.

They can be navigated with a swipe of a finger on touchscreens or conventionally with a keyboard or mouse.

Entering the realm of tablets

This means that Windows 8 will be optimized for use both with conventional computers and touch-operated devices - and one version will be developed to run with the microprocessors made by chip designer ARM which are popular in tablets.

Windows 8 is being seen as being particularly significant economically for Microsoft, as the company hopes to use it to get a better foothold in the lucrative market for mobile devices, in which it has fallen seriously behind.

"Windows has completely reinvented itself," Microsoft's Windows Division Chief Steven Sinofski said during his presentation in Barcelona.

Sinofski joined Windows in late 2006 just after Microsoft's ill-fated Vista operating system had been released to PC manufacturers. He had a big share in bringing out the far more successful Windows 7, which has so far sold 525 million copies around the world.

hg/mll (dpa, AP, Reuters)