There’s been a lot of confusion about Windows 8 and all its versions, and particularly about Windows 8 on the ARM architecture. A lot of people seem to think that the ARM version is just the same as its Intel cousin, but in fact, the two are just a little bit more closely related than Mac OS X and iOS: siblings, if you like, rather than cousins.
First, there’s three members of the Windows 8 family: Windows 8; Windows 8 Pro; and Windows RT. The first two, which are identical other than some enterprise-level added extras, run on Intel processors (but not ARM). Windows RT, on the other hand, runs on ARM only. The first two can also be bought as upgrades for existing machines, while RT is only available to OEMs – and not even all of them.
The next thing you need to know is that Windows 8 supports multiple runtimes (a bit like APIs – so in Mac world, Carbon and Cocoa can be thought of as different runtimes). Win32 is the old, familiar runtime which pretty-much all the Windows applications you know and love (or loathe) are written to. WinRT, on the other hand, is new and is how you create applications which use the new Metro interface.
WinRT is the only way you can create applications which run on Windows RT – apps written for Win32 (i.e. everything you know as a Windows app) won’t run on ARM-based Windows RT machines. And, just to make it more like iOS, on Windows RT you can only install apps from the Windows Store. No more just downloading a binary and running it.
So far, so very like iOS and Mac OS X this is. But there’s a twist: while Windows RT machines can’t run Win32 apps, other versions of Windows 8 can run WinRT apps. So if you buy a copy of (say) a game on your Windows RT-running tablet, exactly the same software should also run on your Windows 8 desktop.
It’s basically as if Apple had allowed Macs to run iOS software in addition to their own OS X applications. Windows RT, which (remember) runs only on ARM, is Microsoft’s “answer” to iOS on tablets. Presumably – because it would be insane to do otherwise – one day it may also migrate down to mobile phones. And my gut feeling is that over time, Win32 will fade away and developers will be cajoled towards only writing WinRT apps.
There’s some question marks. For example, Windows RT includes built-in Office. But will this be feature-complete when compared to the Win32 version running on desktop machines? Or will it be more like the versions of iWork you can get for iOS, which are compatible but nowhere near as feature-rich? My gut feeling is the latter, at least if Microsoft wants to have something that actually performs well.