What are 3 main architectural layers of Windows XP?

Answer 1

The HAL (Hardware Abstraction Layer) creates operating system portability by hiding hardware differences from the upper layers of the operating system. HAL interfaces provide administrative details of low-level facilities. HAL presents a virtual-machine interface that is used by the kernel dispatcher, the executive and device drivers. The executive layer provides a set of services used by all subsystems: object manager, virtual memory manager, process manager, local procedure call facility, I/O manager, security monitor, plug-and-play manager, registry, and booting. The kernel layer provides a foundation for the executive functions and user-mode subsystems. The kernel remains in memory and is never preempted. Its responsibilities are thread scheduling, interrupt and exception handling, low-level processor synchronization, and power failure recovery.