Q: So what's changing from a developer's standpoint?

A: In the technology generations leading up to Longhorn, Microsoft has been moving to a .NET-based managed code environment dubbed WinFX, and the Longhorn generation will finally mark a clean split with the Win32 APIs of the past. That is, Win32 will be in maintenance mode, and all new development will occur with WinFX managed APIs. One such API, Avalon, forms the basis for the new Desktop Compositing Engine (DCE) in Longhorn that replaces GDI and GDI+. These and other new Longhorn APIs will utilize the XML Application markup language (XAML) to make Longhorn more accessible to developers than ever before. The idea is to significantly reduce the number of APIs and make the APIs more standardized. Today, there are over 76,000 Win32 APIs, and countless wrappers. With Longhorn, Microsoft hopes to reduce the API set to 8,000 to 10,000.

Another significant change in Longhorn involves device drivers. In the past, Microsoft allowed customers to use non-signed drivers, which helped compatibility, but caused stability problems. No more: In Longhorn, users hoping to take advantage of the system's exciting new capabilities will only be able to use signed drivers.

Developers interested in Longhorn should examine the Visual Studio 2005 "Whidbey" release, currently in beta, and the Longhorn SDK. which includes developer-accessible UI components and behaviors.

Q: This sounds like a huge change from today's Windows. Will my current applications still work with Longhorn?

A: Yes. Microsoft has even pledged to retain DOS compatibility with Longhorn, though it's currently unclear whether DOS support will be improved over what's available today in Windows XP.

Q: I keep hearing that WinFS is a new file system. Is Microsoft abandoning NTFS?

A: No. WinFS is implemented as an add-on to NTFS and is not a completely new file system. Rather, it is a new storage engine built on the NTFS file system.