It's been a long struggle. In 1981 or thereabouts, a little-known software company called Microsoft managed to get a plum contract with IBM - back then IBM was very much what we would now call the Microsoft of the computing world.

The deal was to supply the disk operating system for the upcoming IBM PC. Bill Gates was off and running.

IBM had been watching the early rise of the microcomputer, especially one little company called Apple which seemed to have found a winning formula in the Apple II. It had a reasonably open little computer (slots for third party cards for printers and so on) and a surprisingly capable operating system which could support a dangerously clever little application called VisiCalc - a spreadsheet. It could also do word processing. IBM thought it prudent to get its own microcomputer out there in case this thing started to take off.

Thirty years later and the wheel has turned (at least once).

Now Microsoft's star appears to be in the descendent and Apple, apparently soundly trumped by Microsoft and IBM in the 1980s, is on the up. As is Google with its Android. Together they look set to clobber Microsoft, according to the Gartner Group analyst Carolina Milanesi.

The key is the switch to mobile and the way the consumer market is now driving the corporate market. So mobile phones (iPhone and Android) are on the rise (while Microsoft has so far failed to make an impact there). Worse yet for Microsoft, tablets are displacing PCs at the consumer end.

By 2017 Gartner says the industry will be shipping about 2.96 billion devices (phones, tablets and PCs). Android will be huge with nearly 1.5 billion devices, Windows will come in second (PCs phones, tablets) with 571 million and Apple's OS (Mac, iPhone, iPad) will account for about 500 million.

That's a huge change and a significant cross-over from 2012 when Windows accounted for 346.5 million devices, Android 497.1 million and iOS/MacOS 212.9 million.

The dynamic, of course, is that mobile is big and growing and the corporate desktop is not. This is bad news for Microsoft because to keep the entire OS show on the road it has to make itself relevant to apps developers and without traction in mobile and consumer it will simply lose scale in the market.

MS will have to move fast to stop the decline.