With Android landing on all-in-one computers and Windows extending its reach deeper into the mobile world, the platform world is tightening into three key teams: iOS and OS X, Windows, and Android.

Chrome OS, BlackBerry, and the other minor players have derivative unit volume, and can therefore be discounted in our larger image of the market.

To compare those three groups yields an irksome, yet interesting, picture. Gartner recently released a set of statistics and prognostications along those operating system niches, stacking the groups against one another. The fine folks over at Redmond Magazine did us the favor of graphing the results.

Here, in a single chart, is the rise of Android, the slippage in the PC market, and Apple’s rising tide:

Microsoft manages to stay atop Apple, but the chart makes it plain that if Microsoft doesn’t want to fall even further behind Android — recall that Android is now being deployed across device classes — it will have to grow its mobile base at a far more rapid pace than it has thus far. Put another way, for Microsoft to chase Google, it can’t lean on the PC market, even as that market category stabilizes.

We can presume that Apple’s growth is mostly iOS-based, given that its OS X offerings are dealing with similar headwinds as Microsoft’s Windows platform.

In July 2013, my colleague Josh Constine and I called Android the new Windows. Recently, Paul Thurrott made the point that 2013 was “the year that Android became the Windows of the mobile world.” In an increasingly multi-modal computing market, where the difference between device classes is blurring, operating systems are becoming more diversely deployed. So, we can’t keep Android unit volume in one bucket, and Windows PC numbers in a separate class.

Microsoft, if it wants to regain the mantle of the leading platform company, has to do more than end the decline in the PC market: It has to ignite its own mobile growth.

Top Image Credit: Flickr