Just about one year ago, Microsoft gave us two new operating systems.

One was a new version of Windows: the one for use with mouse and keyboard, the one whose desktop at this moment lights up hundreds of millions of screens, the one with a software library of four million programs.

The other was a new operating system for tablets. It was modeled on Microsoft’s lovely tiled Home screen for Windows Phones: colorful, clear, elegant, filled with fluid touch gestures. You can’t run Photoshop or iTunes or Quicken on it; this new system requires a whole new type of app. Since Microsoft doesn’t have a name for this OS (it abandoned the names Metro and Modern), I call it TileWorld.

All of this might have been fine, except for one tragic miscalculation: Microsoft mashed these two new operating systems together into something called Windows 8.

Now you have two Web browsers to learn. Two completely different Help systems. Two (actually three) control panels. Two kinds of programs: the traditional ones, which have menus and overlapping windows, and TileWorld apps, which don’t have either of those things.