Microsoft: Only We Get To Use Desktop Mode In Apps For Windows 8 On ARM

Microsoft (NSDQ: MSFT) has cleared up some of the confusion regarding its plans for Windows 8 computers that will use ARM processors, the first time the storied company has built a version of its flagship Windows PC operating system for the chip standard that dominates the mobile world. Windows 8 devices on ARM chips will be able to run a version of Microsoft Office in an operating mode that resembles older versions of Windows, but all other applications aimed at those devices will have to be designed for Microsoft’s new Metro user interface.

With the debut of the “consumer preview” version of Windows 8 now expected later this month at Mobile World Congress, Microsoft’s Steven Sinofsky wrote an epic blog post Thursday on Windows 8 and ARM chips. After Microsoft introduced Windows 8 last year confusion rose over whether or not applications for the ARM versions of Windows 8 devices would be able to run in the legacy “Desktop” mode, and Sinofsky used the opportunity to explain why Microsoft included that Desktop mode on the ARM version of Windows.

“Some have suggested we might remove the desktop from WOA (Windows on ARM) in an effort to be pure, to break from the past, or to be more simplistic or expeditious in our approach. To us, giving up something useful that has little cost to customers was a compromise that we didn’t want to see in the evolution of PCs,” Sinofsky wrote.

But only Microsoft will be able to write applications for that Windows Desktop experience on ARM tablets and PCs: all other developers who want to write applications for Windows ARM devices will have to write them in the Metro style, which also means they’ll have to distribute those applications through Microsoft’s Windows Store. Windows-on-ARM devices will be able to access the legacy Desktop mode from their Metro “Start” menus, but the only things they’ll be able to do in that legacy Desktop mode is run a new version of Microsoft Office (Office 15) designed for touchscreen devices and manage files in the old familiar way.

It’s sort of the best of both worlds for Microsoft. This approach allows it to postpone the creation of a Metro-style of Microsoft Office–perhaps the most useful set of Windows applications–until a later date while encouraging those who want to target Windows 8 devices to focus on Metro.

Windows 8 devices that will run on Intel (NSDQ: INTC) and AMD’s chips will be able to run applications written for the legacy Desktop mode, but developers will be able to use the same development tools to create Metro-style user interfaces for devices using either Intel or ARM (the back-end code, of course, would need to target a particular chip). Given the trends in the computer market these days, focusing just on the Desktop user interface means you’ll be concentrating on the slow-growing portion of the market.

But this is a classic problem for Microsoft; during each technology transition it finds it very difficult to make a clean break from the past given the huge installed base of consumer and corporate applications that run on older technologies. Windows 8 on ARM is an important step forward in that regard, in that anyone who wants their app to run on those devices will have to suck it up and move forward at Microsoft’s speed because older applications written for Intel’s chips won’t run on the ARM devices.

But it seems that even Microsoft can’t do all the heavy lifting to move Office to Metro, at least not right away. That means users will have to switch back and forth between Metro and Desktop in order to access some of Microsoft’s most valuable applications, and that could be jarring, although the Office 15 preview shown off Thursday does indicate that Word and Excel, among others, have been tweaked to more closely resemble the Metro design language.

The company also said that its partners plan to release Windows-on-ARM devices at the same time Windows-on-Intel devices are released, dispelling some fears that the ARM version of Windows might be delayed due to the technical complexity of the project. Most industry observers think those devices are scheduled to arrive around the end of the year, perhaps in time for the holiday shopping season, but Microsoft hasn’t directly addressed a launch schedule.