Microkernel Architecture Like UNIX and VMS, Windows NT has a basic microkernel structure. This means that the heart of the operating system is a relatively small program whose job is to interact with the computer's hardware. Anything the operating system does has to go through this kernel. The greatest advantage of a microkernel architecture is that a single entity is responsible for scheduling of processor time and doling out resources. Essentially, each task that the kernel sends to the processor has a priority associated with it.
Any task can interrupt any lower priority task.
This sounds simple, but the end result is that you can be sure that your most critical programs get the processor time they need at the expense of less important tasks. In addition, the order to kill an application has very high priority, which ensures that simply preempting them can stop wayward applications. Preemptive multitasking makes for a very robust operating system, especially when compared to operating systems that cooperatively multitask, such as Windows 3.1, where a single frozen application could leave you with no choice but to reboot the computer. The Hardware Abstraction Layer is a vital piece of Windows NT, actually serving as bridge between the kernel and the hardware. The function of the HAL is to present the computer's physical resources, such as memory and expansion slots, in a standardized format so that only a single version of the kernel needs to be developed.