Microsoft (Nasdaq: MSFT), the world's biggest software company, announced a revamp of its Office application, which is designed to operate with the company's Windows 8 OS and be available over the cloud.

CEO Steve Ballmer said the new Office will work on other platforms besides the PC, such as the new Microsoft Surface tablet and new phones with Windows 8, which will be introduced later this year.

We're making the new Office as a service first, the Microsoft CEO said during a product launch in San Francisco, so that customers will be able to access it through the cloud, such as with Microsoft's Skype online service. That means customers will be able to sign up to subscribe to a new service called Office 365 via the cloud, rather than just use it in PCs.

He also said the new Office will work with Yammer, the online service Microsoft, of Redmond, Wash. acquired last month. It will also have other features for online meetings, digital note-taking and for making giant displays as big as 82 inches.

Pricing will be announced later, Ballmer said.

Microsoft shares fell 4 cents to $29.35 in late Monday trading.