Longhorn is as different from current versions of Windows as Windows 95 was from Windows 3.1 and offers as much opportunity for users and developers.

Longhorn, and the underlying technologies it brings together, comes as a result of the industry's need to take another look at what we've come to expect from our computers, making radical changes when necessary, while still making sure that existing managed and unmanaged applications and components continue to work.

Based on the .NET Framework

First and foremost, while Windows Server 2003™ embraced managed code by being the first operating system to ship with the .NET Framework preinstalled, Longhorn is the first operating system whose major new features are actually based on the .NET Framework.

This focus on the managed .NET Framework means that to prepare for your Longhorn applications of tomorrow, you should be writing managed code today.

In addition, you should be paying particular attention to the Code Access Security (CAS) model. CAS will be the core security model for the new features, so embracing that model today will help you prepare.

The Pillars of Longhorn

The amount of new technology that's going into Longhorn is so large that it's broken up into pillars, as shown in Figure 1.

Figure 1. The pillars of Longhorn

A pillar is a set of functionality provided in WinFX, which is the name for the newest API set in Windows. The pillars that implement WinFX represent the most fundamental advances in the Windows platform in a decade:

   Fundamentals: supporting the Trustworthy Computing initiative and integrated Click Once application deployment

   Avalon: declarative, vector-based, compositing user interface (UI)

   WinFS: typed, transactional storage integrated at the file system level

   Indigo: reliable, secure, service-oriented messaging

 Features

Additionally, Longhorn will include many other new features, including:

• a completely re-designed user interface, code-named Aero. The new interface is intended to be cleaner and more aesthetic than previous Windows interfaces. The most visible addition to the interface is the sidebar, an area at the side of the screen consisting of tiles which display dynamic information about whatever window is currently in the foreground; this is to some extent an extension of the "system tray" on the Windows task bar.

• a new command-line interface called MSH, and codenamed Monad. It combines the Unix pipes and filters philosophy with that of object-oriented programming.

• full support for the "NX" (No-Execute) feature of processors. This feature, present in AMD's AMD64 architecture, can flag certain parts of memory as containing data instead of executable code, which prevents overflow errors from resulting in arbitrary code execution. This should not be confused with trusted computing facilities provided by a so-called Fritz-chip.

• built-in DVD recording capabilities, including Mt. Rainier support.

• a new installation program that will install Longhorn in about 15 minutes.