US computing giant Microsoft on Tuesday gave the key Chinese market an early peek at its new tablet computer and Windows 8 software, promising a "fast and fluid" operating system.

Microsoft will launch Windows 8 and the Surface tablet computer, designed to compete with Apple's popular iPad, in the United States on Friday. The launch of the two products in China is the same day.

Windows remains the dominant platform for personal computers, but it has lost ground to Apple and Google in newer devices which use rival operating systems.

"With Windows 8, we introduced this fast and fluid experience that works across a broad range of different types of PCs (personal computers)," said Steven Sinofsky, president of Microsoft's Windows division.

"Windows 8 seamlessly moves between a world of touch-only tablets to laptops that have touch screens to desktops and to portable computers without touch screens," he said in a speech to the media in Shanghai.

Microsoft's new tablet computer was designed to be a platform for Windows, Sinofsky said, as he compared the challenger to Apple's iPad.

"Even though it's bigger than an iPad, it's actually lighter in your hand because of the way the physics of the design work," he said.

The Surface has a full-sized USB port unlike the iPad, a built-in stand and a cover which doubles as a keyboard, he said.

It runs the new Windows RT, a form of Windows 8, and comes with Microsoft Office 2013.

It is not Microsoft's first foray into the tablet market. In 2000 the company unveiled a prototype tablet PC and shortly afterwards began licensing its specifications to various manufacturers.

An analyst said Microsoft's tablet would battle for market share in China, which has the world's largest number of Internet users at more than 500 million.

"It doesn't have a price advantage over the iPad, so consumers who can afford a tablet may still be inclined to choose Apple's iPad," said Gerry Xu, of global information company IHS.

Some who have tested Windows 8 complain about the change from earlier versions of Windows, which could force users to relearn how to operate their computers, the New York Times reported Sunday.

Sinofsky acknowledged the difference with older versions but said Windows 8 was designed for the "modern world".

"It's a completely different feel. It's clean. It's beautiful. It's intuitive," he said.

Sinofsky said Microsoft hoped to add up to a billion new customers with Windows 8, which aims to replace earlier versions of its dominant operating system.

"It's (Windows) used by over a billion people around the world and with Widows 8 we're aiming towards the next billion," he said.

Microsoft has been hurt by piracy in China. Industry group the Business Software Alliance last estimated in 2008 that 80 percent of software used in China was pirated.

Ralph Haupter, Microsoft's chairman and chief executive officer for the Greater China Region, said the mainland was an important market.

"China is a big business opportunity for us. China is also the place where many devices get developed, designed, built, but these days, even more importantly, get sold," he told reporters.

A company spokesman said Microsoft does not release sales and revenue figures for China alone.