Microsoft on Friday made Office available on iPhones for people who pay to use the popular productivity software as a service in the Internet cloud.

A free Office Mobile application for iPhones hit the shelves of Apple's App Store but can only be used with subscriptions to Office 365 Home Premium or Office 365 ProPlus.

Subscriptions to Office 365 cost $100 a year and allow the suite of programs for documents, spreadsheets, presentations and other tasks to be used on as many as five devices -- in a nod to modern, multi-gadget lifestyles.

Documents or other files created using Office programs can be saved at Microsoft's online SkyDrive.

"The iPhone app enables great Office content viewing and on-the-go content editing capabilities," Julia White, general manager of Microsoft's Office division, said in a blog post.

"After signing in to an Office 365 account, you can access, view and edit Microsoft Word, Excel and PowerPoint documents from anywhere."

Microsoft in January began letting people subscribe to Office as a service in the Internet cloud, shedding the need to buy the popular productivity software on a disk.

"It's kind of a reflection of how most of us live nowadays," company official Oliver Roll said at the time. "The same way you get instant access to movies or music at Netflix or Spotify, you access your documents in the cloud."

Microsoft earlier launched a version of Office 365 for businesses.

The Office suite includes Word, Excel, and OneNote.

Shifting Office into the cloud comes as Microsoft adapts to a world in which people are renting software on the Internet instead of paying to take home the kind of packaged programs on which the company's empire was built.

The Redmond, Washington-based software giant's competition includes a suite of online applications hosted by Internet powerhouse Google.

Microsoft is also keen to stay in tune with the lifestyle shift to smartphones and tablets despite failing to score hits with mobile devices powered by its Windows software.