What you will learn in this module:

• The key features of each member of the Windows 2000 product family
• The system architecture of Windows 2000

The Windows 2000 Family

Windows NT has been with us for almost eight years, and as the product has matured, Microsoft have added more features in an effort to address users' needs and administrators' requirements.

With Windows 2000, they have made considerable enhancements to the product line.

Windows 2000 Professional is the preferred 32bit desktop environment, providing a combination of Windows 98 usability and Windows NT 4 reliability. New features include support for power management and plug and play (a great bonus for portable users) and support for new file system features, including EFS.

Windows 2000 server has been created in three different flavours, each with features appropriate to the target audience. All share the same core features as Windows 2000 Professional, but then add additional features.

Windows 2000 Server is the standard, entry level server platform providing similar power to the Windows NT 4 Server product. However, it also includes support for Terminal Services and Active Directory.

Users requiring more power should opt for Windows 2000 Advanced Server, similar in power to Windows NT 4 Enterprise Server. It provides enhanced scalability and clustering support.
Users who need Enterprise size database or web servers should opt for the Windows 2000 Datacentre Server. This is currently the most powerful server product in the range.



System Architecture



Windows 2000 supports programs running in user mode and programs running in kernel mode. All of the Windows 2000 subsystems and applications run in user mode, and each subsystem and application runs in its own protected address space.

This layered approach provides reliability, stability and extensibility.

Windows 2000 employs a layered model in the kernel-mode portion of the operating system. At the lowest layer is the Hardware Abstraction Layer (HAL). On top of the HAL is the kernel, which is the lowest layer in the executive.

On top of the kernel is the rest of the Windows 2000 executive components. The kernel performs low-level operating system functions such as thread scheduling and exception and interrupt handling. The HAL is a layer of platform-specific code that protects the kernel and the rest of the executive from platform differences - although the predominant platform has always been Intel based. The HAL manipulates hardware directly.

The remaining components of the executive provide system services to the environment subsystems. They interact with each other through a set of well-defined formal interfaces.

The HAL

The HAL consists of a series of functions that hide or abstract differences between hardware platforms. However, although the driver is still a key component of Windows 2000, Microsoft's support for non-Intel based platforms is waning - due to lack of user interest in non-Intel platforms.