Ever since Steve Ballmer made that surprise announcement at CES 2011, there has been a lot of speculation about just how Microsoft would be bringing Windows to the ARM architecture. Would it be a whole separate line? Would it be compatible with old applications? Would it be cheaper?Many of these questions have been answered in a long and technical post on the Building Windows 8 blog today, as Steven Sinofsky explains how they developed (re-developed, really) Windows On ARM, or WOA, and why they made the choices they made.Some major points, for those unwilling to read: WOA will be totally incompatible with x86/x64-based applications; it will include a desktop only for Office apps and file management; it will be focused on portability, battery life, and “integrated quality.”