See hardware abstraction layer (HAL).


An opaque type that represents a reference to an object. For more information see the topic, Object Handles.

hardware abstraction layer (HAL)

An NT-based operating system component that provides platform-specific support for the NT kernel, the I/O manager, kernel-mode debuggers, and the lowest-level device drivers. The HAL exports routines that abstract platform-specific hardware details about caches, I/O buses, interrupts, and so forth, and provides an interface between the platform's hardware and the system software. For example, the HAL implements a routine to map each device driver's bus-relative device interrupt vector to a system-assigned vector with a corresponding platform-specific hardware priority (DIRQL), as well as several routines that provide DMA-transfer support.

hardware branch

The hardware archive root key in the registry that is a superset of the memory-resident hardware tree. Although the hardware tree contains information only about those devices currently detected and running in the system, the registry contains a complete list of all hardware ever installed on the particular computer. The hardware root key is \\HKEY_LOCAL_MACHINE\Hardware.

hardware compatibility tests (HCT)

A suite of tests from WHQL to verify hardware and device driver operations under a specific operating environment. These tests exercise the combination of a device, a software driver, and an operating system under controlled conditions to verify that all components operate properly.

hardware exception

See structured exception handling.

hardware ID

A vendor-defined device identification string that Setup uses to match a device to an INF file.

For more information, see the topic Device Identification Strings.

See also device ID, compatible ID, instance ID, and device instance ID.

hardware key

A device-specific registry subkey that contains information about the device. Also called a device key. For more information see the topic, Registry Trees and Keys for Devices and Drivers. A driver package can add settings via an INF by using an HKR specification in an add-registry-section referenced by a DDInstall.HW section.

See also software key.

hardware priority

See IDT and IRQL.

hardware profile

A set of instructions that tells Windows which devices to start when you start your computer or which settings to use for each device. For information about how you can create a hardware profile, see Windows Help and Support Center.

hardware tree

A record in RAM of the current system configuration based on the configuration information for all devices in the hardware branch of the registry. The hardware tree is created each time the system is started or whenever a dynamic change occurs to the system configuration.


Host bus adapter. A hardware device that "connects" the operating system and a SCSI bus. A SCSI miniport driver manages the lower layers of the SCSI-II protocol on the HBA.

See miniport driver. See also port driver, class driver, SFD, and SCSI.


See host controller driver (HCD).


See hardware compatibility tests (HCT).


A handle to a device object. Every NT-based operating system display driver needs a handle to its device object; this handle is of type HDEV. An object of this type is created by GDI at driver initialization and is stored by the driver for use when calling GDI engine services.

The term , in lower-case, is typically used as the name of a function parameter or structure member of type HDEV.


See pool memory.

heap manager

The portion of the display driver responsible for managing the frame buffer memory.

Heatherington escape sequence

A reliable technique used in modems to switch between data mode and command mode.

hibernate state

System power state S4, in which power is off exactly as for the shutdown state (S5), but the system can resume quickly from a file written to disk before power down.

hibernation file

A system-image file that is written to disk immediately before a system transition to system state S4. On reboot, the hibernate file is loaded so that the system can resume from its previous location.


Human Interface Device.


A callback function that handles I/O port and board memory accesses. Synonymous with handler.

host controller driver (HCD)

For USB, HCD defines a driver stack that controls the USB chipset to which a device is attached.

host CPU

In DirectX video acceleration, the programmable processor that controls the overall function of video decode (high-level operations).

host-based controller

See controllerless modem.

host-based IDCT

In Microsoft DirectX VA IDCT is performed on the host decoder with the decoder passing blocks of spatial-domain results to the accelerator for external picture reconstruction.

See also IDCT.

hot docking

Inserting a portable computer or other mobile system into a base unit while the mobile system's power is fully on.


A geographic location which provides public Internet access through a local wireless LAN (WLAN).


The color tint of an image. The color of the analog video signal is determined by three factors: hue, saturation, and luminance.


A call made by partitions to the hypervisor.


A block of virtual memory somewhere in kernel space, dedicated to the use of the memory manager. Every instance of a user-mode virtual address space has an associated hyperspace area where the memory manager maintains internal data (such as page table pages and WSLs) for the current process.

See also kernel space and user space.


A layer of software that runs above the physical hardware and below one or more operating systems to provide isolated execution environments that are called partitions.



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