By 2016, devices running Windows will be eclipsed by phones and tablets running Google's Android, according to a report by analysts IDC.
More than 90 per cent of the world's PCs still run Windows - but the whole technology landscape is changing around Microsoft's operating system.
By 2016, Microsoft's leading market share of 35.9% will slip to 25.1%.
Devices running Google's Android will climb from 29.4% to 31.1%.
As smartphones grow in relation to PCs, Microsoft's market share will slide so that its once-dominant Windows software will be second-placed after Google's Android
Microsoft is to launch a new 'tablet friendly' version of Windows, Windows 8, later this year.
But analyst IDC still predicts a 'dramatic shift' towards devices running Android.
'IDC expects a relatively dramatic shift between 2011 and 2016, with the once-dominant Windows slipping from a leading 35.9% share in 2011 down to 25.1%,' the analyst predicts.
The number of Android-based devices running on ARM CPUs, on the other hand, will grow modestly from 29.4% share in 2011 to a market-leading 31.1% share in 2016.
Meanwhile, iOS-based devices will grow from 14.6% share in 2011 to 17.3% in 2016.
Last year, 916 million smartphones, tablets and PCs were shipped worldwide.
By 2016, that figure will have doubled to 1.84 billion units.
‘Android's growth is tied directly to lower-priced devices,’ said Tom Mainelli, research director, Mobile Connected Devices. ‘So, while we expect dozens of hardware vendors to own some share in the Android market, many will find profitability difficult to sustain.’
Samsung's mid-sized Galaxy Note device which recently passed 5 million units shipped: In the next four years, Android devices are predicted to pass Microsoft's Windows in terms of units shipped
‘Whether it's businesses looking at deploying tablet devices into their environments, or educational institutions working to update their school's computer labs, smart, connected devices are playing an increasingly important role in nearly every individual's life,’ said Bob O'Donnell, vice president, Clients and Displays at IDC.
Next year, 1.1 billion 'smart devices' - smartphones, PCs and tablets - will ship worldwide.
The numbers are growing at a compound annual growth rate of 15.4%.
Research conducted by IDC suggests that many individuals own and regularly use multiple smart connected devices.
‘We are in the multi-device age,’ continued O'Donnell, ‘and we believe the number of people who use multiple devices will only continue to increase.
'The trick, moving forward, will be to integrate all these devices into a unified whole through use of personal cloud-type applications and services.
'That's the real challenge of what we have often called the "PC Plus" era.’
‘Smartphone growth will be driven by Asia/Pacific countries, especially China, where mobile operators are subsidizing the purchase of 3G smartphones, thus increasing the total addressable market.
In many if not all instances, the smartphone will be the primary connection to the Internet,’ said Will Stofega, program director, Mobile Phone Technologies and Trends.