Microsoft Unveils Its Next Operating System, Windows 8

BARCELONA — Microsoft showed off the newest version of the company’s operating system, Windows 8, on Wednesday.

Windows 8 is the biggest redesign of the company’s software since Windows 95, said Steve Sinofsky, the president of Windows, who introduced the new operating system during the Mobile World Congress at a poolside event where waiters handed guests glasses of champagne and small tapas and snacks were served.

“Windows 8 is a generational change in the Windows operating system in the design, functionality and implementation,” Mr. Sinofsky said.

Microsoft has planned two versions of its Windows 8 software. One is designed around a touch interface and will be available on Microsoft tablets, and the other is for PCs and is designed to work with a mouse and keyboard. Both share the same aesthetic and navigation.

Mr. Sinofsky said the company had worked to make sure that people who were switching between using Windows on a smartphone, tablet and laptop would not be confronted with any break in their use of the software as they cycled between devices.

“There are too many hard stops between tablets and devices and smartphones,” he said. “This makes them much more harmonious and seamless.”

Julie Larson-Green, the head of design for Windows 8, demonstrated the new software on a specially designed Samsung tablet; she said the company aimed for the interactions with the software to be “fast and fluid.” The new interface, which looks similar to the software used by Microsoft’s new line of smartphones, Windows Phone, takes some cues from the app-centric home screens popularized by Apple and Google. It revolves around animated tiles, called Metro.

After a user signs in to his Microsoft account, the software populates the tiles on his home screen with information from accounts around the Web, including Facebook, Twitter and Skydrive, Microsoft’s cloud-based storage system. Ms. Larson-Green said several applications would also come installed on the Windows 8 software, including Xbox Live, Internet Explorer, and a custom-built video and music player that lets users purchase and stream albums and movies. For Windows users who prefer the familiar, drag-and-drop desktop-oriented layout of the operating system, a desktop application whisks away the tiles to reveal the original Windows interface.

Although Microsoft demonstrated an earlier version of the Windows 8 software last fall, Mr. Sinofsky said the company had made more than 100,000 changes to the code, based on feedback from developers and designers who tested the early version. The preview is available for download, although Microsoft executives did not provide details about when the software would officially go on sale. During the preview, however, users will be able to download applications from a Windows Store, although the only applications available will be free. The company will add a buying mechanism, most likely before the final version of the software is released.

“It’s the only operating system that lets you switch between devices,” Mr. Sinofsky said. “So you can truly pick the form factor that you want to use without compromising.”