Windows architecture

On of the design goals of Windows NT was portability.

This goal is mainly achieved by sepearting the functionality that is hardware dependent from the functionality that is hardware independent.

Hardware dependent functionality is placed into the Hardware Abstraction Layer (HAL) which is implemented in hal.dll

The independent functionality is placed into the kernel and is implemented in ntoskrnl.exe.

In order to have a portable code base, most of ntoskrnl.exe was written in C or C++.