As we build applications for more and more platforms, it is extremely important that we maximize our code reuse across platforms. With the release of Windows 8 and Windows Phone 8, Microsoft has made significant improvements in platform convergence – this convergence will continue with each release. They share the same core as Windows, and Microsoft removed .NET compact framework and replaced it with CoreCLR and added WinRT. Much of this is common to Windows 8 itself.
However, it is important to understand that these are still two distinct platforms and still do not have 100% convergence with binary compatibility. Maximizing reuse across these platforms is key to an efficient development experience.