On its, comments by Microsoft CEO Satya Nadella that the company was working toward "one Windows" set off imaginations about what could be a greatly simplified operating system proposition for both developers and consumers.
As Mary Jo Foley reported on CNET sister site ZDNet, Microsoft went on to couch the statement. Windows would continue to come in several versions, and most of its "convergence" had to do with the teams working together in one department, something that has been in place for some time.
Still, what if Microsoft really tried to create one version of Windows that ran on laptops, tablets, and phones using either x86 (Intel or AMD) or ARM (Qualcomm, Nvidia, and so on) processors? In addition to having to reconcile a fair amount under the hood, there would be significant user interface differences between the desktop, tablet, and handset flavors of Windows.
The desktop. Easily the biggest difference among Windows Phone, Windows RT, and Windows 8.1 is the presence and functionality of the desktop. When compared with Apple, Microsoft has long been a stronger champion of backward compatibility, but this has haunted the company as it has attempted to extend its dominance of x86-based PCs. Microsoft's dilemma is that it can't live without the desktop, but when it comes to ARM-based tablets and phones of any stripe that fit in one's pocket, it also can't take it with them (at least with full backward compatibility).
Microsoft can't really kill the desktop and probably never will. One thing it can do -- and indeed has been trying to do -- is encourage development of more Modern applications that can scale to all environments to the point where the desktop is the kind of niche environment the command line is today; it could also better align the Windows tablet and phone experiences by removing the mostly vestigial desktop on Windows RT. Of course, Microsoft could greatly help its own cause here by releasing a Modern version of Office; we've already gotten a decent preview of what such a product might look like in the well-regarded iPad version.
Another option would be to stop trying to force the Modern interface on desktops and create its own variation of the desktop-touch dichotomy that Apple uses. In Microsoft's case, though, the separation wouldn't be so much by device but in usage scenario or user preference. This seems to be the direction in which the company is heading.
Back button. iOS has no universal back button; Android does (even if it's on the screen). But in both cases, the use of the interface element is consistent across phones and tablets. That's not true in the Windows world, which treats tablets as a closer cousin to the laptop. Microsoft would have to choose. It might opt to get rid of the back button, perhaps allowing people to swipe the Windows logo to activate the feature.
Camera button. A camera button makes a lot of sense on a phone, but a lot less sense on a laptop or desktop. However, as Microsoft has looked at making the Windows Phone OS available on less expensive handsets, it has already dropped the requirement. Now, phones without the extra button, which could be used for Android, can also be used for Windows Phone.
Snap. One of the things that sets apart Windows tablets like the Surface from the iPad is the support for two apps on the screen at the same time using a feature called Snap. A number of Android tablets and phones from Samsung and LG have implemented this, but it's not a universal feature. Windows phones such as the Lumia 1520 certainly have the real estate for such a feature.
Task switching. Windows and Windows Phone have different ways of choosing among apps. Windows introduced a way of browsing recent apps in a manner similar to the way other mobile operating systems -- including WebOS, the Playbook OS, and now iOS -- do, by showing thumbnails of recent apps. But desktop Windows ' task switcher is invoked by swiping from the left and then swiping back, although one can also rotate among open apps by swiping to the right. The interface may not be obvious, but it's more flexible; it would be great to see it simplified and standardized.
Charms. One of the most undersold features of Windows 8, "charms" are those little round buttons that show up when you swipe from the right, but they're not there in Windows Phone. They should be, though. Like Snap, this is the kind of feature that makes sense as the average size of Windows Phones grows.