Summary Box: Microsoft unveils Windows 8 for test

THE MILESTONE: Microsoft let consumers start trying out its upcoming touch-based Windows 8 operating system.

ABOUT THE SYSTEM: It aims to power a new wave of tablet computers and traditional PCs designed to counter Apple’s big gains in the market through its Macs and iPads.

DEMOS: Microsoft executives at the Mobile World Congress show in Barcelona showed off how users can use their fingertips to swipe in and out of applications, and tilt upright computer screens to a flat position so they can be used as two-person gaming boards or big drawing tablets.