This article was previously published under Q99588
The Windows NT hardware abstraction layer (HAL) refers to a layer ofsoftware that deals directly with your computer hardware. Because theHAL operates at a level between the hardware and the Windows NTexecutive services, applications and device drivers need not be awareof any hardware-specific information. The HAL provides routines thatenable a single device driver to support a device on differenthardware platforms, making device driver development much easier. Ithides hardware dependent details such as I/O interfaces, interruptcontrollers, and multiprocessor communication mechanisms. Applicationsand device drivers are no longer allowed to deal with hardwaredirectly and must make calls to HAL routines to determine hardwarespecific information. Thus, through the filter provided by the HAL,different hardware configurations can be accessed in the same manner.
Microsoft Windows NT "Resource Guide"
"Inside Windows NT," Helen Custer, Microsoft Press, 1993