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Operating System
Notes Figure 14.1: Windows 2000 Block Diagram
The hybrid kernel sits between the HAL and the executive and provides multiprocessor
synchronization, thread and interrupt scheduling and dispatching, trap handling and exception
dispatching. The hybrid kernel often interfaces with the process manager and is responsible
for initializing device drivers at boot-up that are necessary to get the operating system up and
running.
14.3 Environmental Sub-systems
Environmental subsystems are user-mode processes layered over the native Windows 2000
executive services to enable Windows 2000 to run programs developed for other operating
systems, including 16-bit Windows, MS-DOS, POSIX, and character-based applications for 16-bit
OS/2. Each environmental subsystem provides one API or application environment.
Windows 2000 uses the Win32 subsystem as the main operating environment, and thus to start all
processes. When an application is executed, the Win32 subsystem calls the VM manager to load
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