(Pocket-lint) - Greg Sullivan, Senior Product manager for Windows Phone, has told Pocket-lint that the company opted out of creating a phone version of Windows RT (the tablet version of Windows 8) because it felt that having the two operating systems still made very good sense, for the moment.

In an interview with Pocket-lint in London following Tech Ed in Europe, Sullivan detailed how - while the two platforms are very close in what they can offer - Microsoft believes that it is worth keeping the two separate, while at the same time allowing the two to benefit from each other to beat the iPad.

"We believe the phone - and the aspect ratios of the phone form factors - is unique enough to devote a specific effort to building a phone operating system and differentiating that," he said.

"Will there be more of this convergence we are seeing between Windows 8 and Windows Phone 8 in the future, absolutely, it makes a lot of sense. We still think there will be a discrete offering, but you will get more and more of this efficiency that we are beginning to get with Windows 8 and Windows Phone 8.

Sullivan went on to explain: "There are meaningful differences between the two. Take iOS: while the iPhone and iPad versions look the same, underneath they are very different. If you write an app for both of them you have unique code that is targeting the different devices.

"Our approach is really not any different except they [Apple] drew a line between phones/tablets and then the Mac, while we've drawn a line between the phone and the tablet/PC operating systems. We have a significant amount of code reuse, we have the same device driver code, we have a similar user experience with Metro."

Sullivan believes that in the long run this should help Microsoft gain the upper ground and help it show the iPad's forthcomings.

"When I use an iPad I think it’s a really pleasurable experience, it’s a great consumption device, but I constantly run into guardrails. I want to connect a USB mass storage, oh a can't. I want to print to a printer other than the one Lexmark or whatever, I can't. I keep wanting to do things I can't do. I think it's primarily because of the fundamental strategy where they took a phone OS and stretched it up to a tablet.

"We are taking a PC OS and shrinking it down. We could have done the same thing, but it doesn't make sense. When we deliver Surface or any Windows 8 device, the Pro model will run every Windows app ever written. That think will run Visicalc 1.0 from 1981. I saw a demo. It's amazing. It's part of the promise."

Given Apple's history and success with the iPhone, Sullivan said he completely understood why Apple made the choices it did, and why Microsoft was coming at it from the direction it is.

"Apple was coming from their area of strength. They own the API in the mobile space. It made more sense for them to go with their area of strength and stretch the API so developers could benefit from that [with the iPad]. In their true way they've done an elegant well integrated one.

"People have asked us why we haven't just put Windows Phone on a tablet and said it's good, that's what Apple did? But our approach in fundamentally different and the long-term benefits mean I won't run into those guardrails, there will be printer drivers, everything will work, and those things will keep adding up and adding up. I think our approach will end up with a much more powerful functionality, less limited, less constrained device."

Sullivan added: "They draw the line between the phone/tablet and the PC, and we are drawing the line between the PC/tablet and the phone.

"Over time we will already, in Windows Phone 8, share more things like the architecture, and user experience level, and as I hinted that kind of convergence will mean it will make more sense to invest in our platform in the future."

Writing by Stuart Miles.