You may not realize it but there’s actually three flavors of the Windows operating system, which can run on a variety of different devices, namely Windows 8, Windows RT and Windows Phone. If you think Microsoft’s strategy here is a little confusing – well, so does it, which is why the company is slowly edging towards a future with only one Windows for everything.

This much can be inferred from Microsoft’s head of devices, Julie Larson-Green, who said at last week’s UBS Global Technology Conference that the company is working towards merging its main operating systems.

“We have the Windows Phone OS. We have Windows RT and we have full Windows. We’re not going to have three,” said Larson-Green.

Obviously, with the noticeable absence of a clear roadmap – and a CEO – none of this is cut and dried, but Larson-Green’s comments suggest that Microsoft is already moving towards a merger of Windows RT, the version of Windows that runs on ARM devices, with Windows Phone, which runs on the NT kernel but is also compatible with ARM. This will take some work, because its said that only 33 percent of Windows RT and Windows Phone APIs are currently compatibile, though Microsoft is aiming for 77 percent compatibility with its next “Blue” update, and full compatibility by 2015, reports ZDNet’s Mary Jo Foley.

Windows RT is a more sophisticated version of the OS than Windows Phone, but the latter appears to be the favorite at this moment in time – it’s believed that Microsoft is working to scale Windows Phone to run on 7-inch and 10-inch tablets, something that could signal the end of the road for RT.

So why is Microsoft doing this? Well, according to Larson-Green, it’s all about mobility.

“We do think there’s a world where there is a more mobile operating system that doesn’t have the risks to battery life, or the risks to security,” she said. “But, it also comes at the cost of flexibility. So we believe in that vision and that direction and we’re continuing down that path.”

There’s also no doubt that Windows RT has left a lot of consumers confused, as Larson-Green admits:

“I think we didn’t differentiate the devices [Surface RT vs. Surface Pro] well enough. They looked similar. Using them is similar. It just didn’t do everything that you expected Windows to do. So there’s been a lot of talk about it should have been a rebranding. We should not have called it Windows. How should we have made it more differentiated? I think over time you’ll see us continue to differentiate it more,” she said.

Larson-Green also dropped a few more hints about Microsoft’s future strategy during the interview. She spoke of her vision of a future, where users possess multiple different devices or phones, perhaps as many as “three of four”, that they can switch between, depending on the scenario.

“I have that six-inch one [presumably the Nokia 1520 or a device like it],” said Larson-Green.

“And when you’re traveling on the train and you’re using public transit so you can see more and do more, and then when you’re out in the evening and you only have your suit, or your evening dress, you have a small one that slips in your pocket. You can buy more than one.”