The revamped Office makes use of cloud computing and is compatible with touch screens widely used in tablets. It comes as Apple Inc and Google Inc make inroads into the workplace, long Microsoft's stronghold. Office is Microsoft's single-biggest profit driver.
"The Office that we'll talk about and show you today is the first round of Office that's designed from the get-go to be a service," Microsoft Chief Executive Steve Ballmer told reporters. "This is the most ambitious release of Microsoft Office that we've ever done."
Microsoft has a lot riding on the 15th version of Office. Windows is one of the world's biggest computing platforms, and the Office applications -- Word, Excel, PowerPoint, and other tools -- are used by more than 1 billion people around the world.
Microsoft last updated Office in 2010, when it incorporated online versions for the first time. The full version of Office 15 is expected to be available in early 2013.
Cloud computing refers to a growing trend toward providing software, storage and other services from remote data centers over the Web instead of relying on software or data installed on individual PCs.
"Your modern Office thinks cloud first. That's what it means to have Office as a service," Ballmer said, adding that a preview version of the software is now available online.
