Microsoft on Tuesday 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," said company official Oliver Roll. "The same way you get instant access to movies or music at Netflix or Spotify, you access your documents in the cloud."

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.

"We should be able to get our content on all our devices, and it shouldn't be a hassle," said Roll, who is the Office division's general manager of communications.

Documents or other files created using Office programs can be saved at Microsoft's online SkyDrive with storage space beefed up to 27 gigabytes for subscribers.

Office 365 also comes with 60 minutes of international calls to landlines using online telephony service Skype, which is owned by Microsoft.

"You get the rich Office applications on your computer as if you had bought the traditional license," Roll said.

"The difference is you will be updated more frequently; have the latest features and work across five devices instead of one."

Microsoft launched Office 365 for businesses about 18 months ago, and companies large and small have been rapidly signing on, according to Roll.

On February 27, Microsoft will roll out a new business version of Office 365 optimized for the freshly-released Windows 8 operating system, the company said.

Office software in old-fashioned packaged disks also went on sale Tuesday.

Still, "I think there will be a point in the future where nearly all, if not every one of, our customers choose to buy Office as a service in a subscription," Roll said.

"There is so much value to working from wherever you are, across all your devices, personalized and with software that is always up to date."

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.

But "Office 365 is head-and-shoulders above anything else out there," Roll said. "That is why customers are choosing us; with Google Apps they are compromising and people don't want to compromise."