Microsoft has confirmed that Windows Mobile applications will not be able to run on the smartphone platform's replacement, Windows Phone 7 Series.
Announced in February at Mobile World Congress 2010, Windows Phone 7 is a substantial revamp of Microsoft's existing handset operating system. At the announcement, Microsoft did not say whether or not old apps would run on the new platform.
On Thursday, Microsoft's head of development for the OS, Charlie Kindel, revealed that there will be no compatibility between the old and the new.
"For us, the cost of going from good to great is a clean break from the past," Kindel wrote. "To enable the fantastic user experiences you've seen in the Windows Phone 7 Series demos so far we've had to break from the past. To deliver what developers expect in the developer platform we've had to change how phone apps were written.
"One result of this is previous Windows mobile applications will not run on Windows Phone 7 Series."
Kindel added that Microsoft will continue to work with its partners to produce devices based on Windows Mobile 6.5 and will support those products for many years to come. "It's not as though one line ends as soon as the other begins," he wrote.
The development tools that will be needed to write applications for Windows Phone 7 are .NET, Silverlight, the XNA game development platform and "Web 2.0 standards", Kindel said. Windows Mobile 6.5 also required .NET, but the use of Silverlight and XNA may be new to developers writing for Microsoft's mobile platform.
"The expertise and familiarity with our tools is not lost," Kindel wrote. "If you are a .NET developer today your skills and much of your code will move forward. If you are Silverlight or XNA developer today you're gonna be really happy. New developers to the platform will find a cohesive, well-designed API set with super-productive tools."
Further details about Windows Phone 7 development are expected at Microsoft's MIX10 developer event on 15 March.