FAQ: All about Windows RT, the OS behind a Microsoft tablet

Computerworld - The Internet began boisterously buzzing last week that Microsoft will unveil its own tablet later today, perhaps one powered by Windows RT, the offshoot of Windows 8.

On Monday, the speculation grew even more adamant, with the New York Times claiming that Microsoft sources told it that the company will indeed introduce its own tablet, and that the device would run Windows RT.

While Microsoft has aggressively touted Windows 8 with scores of blog posts spelling out often picayune details of the upcoming operating system, the company has been relatively quiet about Windows RT, the all-mobile OS destined for tablets. How is Windows RT different from its better-known cousin? Why did Microsoft create two versions when Windows 8 also boasts some of the same features and relies, at least in part, on the same design motif and user interface (UI)?

Questions, questions, questions.

And because there's a growing chance Microsoft will make a landmark move -- it's never directly competed with its PC- or tablet-making partners -- we have some answers.

Where do I buy Windows RT? You don't. Not separately, anyway, as Windows has been sold for decades. Windows RT is OEM-only -- OEM, for "original equipment manufacturer" is simply a computer maker, like Dell or Hewlett-Packard or Lenovo -- and the OS can't be purchased by individuals or Microsoft's corporate customers.

Instead, it is pre-installed on devices, most likely tablets, although Microsoft has been trumpeting a claim that at some point, low-cost, power-miserly notebooks will also run the OS.

The rumored tablet that Microsoft is to unveil later today would run Windows RT, making Microsoft its own OEM for the first time ever for a computer or computer-like device.

So Windows RT is the same as Windows 8? No, it's not. They're two separate lines of Windows, and to delve into family history, cousins at best -- maybe once removed.

Think of it this way: Windows RT is to Windows 8 as Apple's iOS is to OS X. The two within each pair clearly have a shared history, some shared code, but are distinct operating systems designed for different classes of devices, and run on completely different, and incompatible, processor platforms.

Both OS X and Windows 8 run on Intel's x86/64 processor architecture, while iOS and Windows RT work only on devices with ARM-licensed CPUs.

So I'm guessing that apps designed for Windows 8 -- or older version of Windows -- won't run in Windows RT. You are correct. Programs designed for Windows 8, the operating system that runs on devices powered by Intel's x86/64 processors, will not only not run on Windows RT, they're not even allowed to try. With a few exceptions..., because there are always exceptions.