DCT

DCT

Discrete Cosine Transform. A technique used to achieve spatial compression of a video stream. It transforms a block of pixel values into a set of "spatial frequency" coefficients. See also IDCT

discretionary access control list (DACL)

Part of the security descriptor for an object. The DACL can be applied to a newly created object in order to restrict access to the object.

See also ACE, access right, ACL and security descriptor.

disk controller

A special-purpose chip and circuitry that directs and controls reading from and writing to a computer’s disk drive. Also called a hard disk controller (HDC).

disk extent

A contiguous run of sectors on one disk.

dispatch routine

An IRP-processing routine in a kernel-mode driver. Drivers export entry points for these routines through a dispatch table in the DRIVER_OBJECT structure.

For more information see the topic, Writing Dispatch Routines.

dispatch state

At any given moment, a thread can be in one of the following states:

initialized
ready – queued and eligible for dispatch to a processor
standby – ready and selected to execute, but a context switch to the thread has not yet occurred
running
waiting – suspended until a particular dispatcher object is set to the Signaled state
terminated

dispatcher objects

A class of kernel-defined object types that are used to manage dispatching and synchronization. See also control objects.

Dispatcher objects have a state (either Signaled or Not Signaled), and are arguments to the wait services or kernel wait routines (KeWaitXxx). Dispatcher objects include: events, (kernel-mode-only) mutexes, queues, semaphores, threads, and timers.

Kernel-mode threads synchronize their operations by waiting on one or more dispatcher objects, or by waiting on other objects, such as user-mode file objects, that contain "hidden" kernel-mode dispatcher objects.

It is a fatal error to wait on a dispatcher object at IRQL >= DISPATCH_LEVEL.

display power management signaling (DPMS)

A standard that defines display power management states and provides a standard method for the display controller to signal to the display to enter into those states.

distribution system (DS)

The backbone that connects the access points of an 802.11 LAN. The distribution system can use Ethernet or another wired or wireless network architecture.

dithering

A technique used to create the illusion of varying shades of gray on a monochrome display or printer, or additional colors on a color display or printer. Dithering treats areas of an image as groups of dots that are colored in different patterns. Similar to halftones in photography.

DLL

Dynamic-link library.

DMA

See direct memory access.

DMI

Desktop Management Interface. A framework created by the DMTF.

DMTF

Desktop Management Task Force. DMTF specifications define industry-standard interfaces for instrumentation providers and management applications.

dock

To insert a portable computer into a base unit. Cold docking means the computer must begin from a power-off state and restart before docking. Hot docking means the computer can be docked while running at full power.

See also warm docking.

docking station

The base computer unit into which a user can insert a portable computer, expanding it to a desktop equivalent. A typical docking station provides drive bays, expansion slots, the ports that would be provided by an equivalent desktop computer, and AC power.

document-sticky

A printer property page setting that applies only to a single document. For example, the left and right margins of a particular document are document-sticky settings.

Contrast with printer-sticky.

dongle

A physical device, attached to a PC's I/O port, that adds hardware capabilities.

DPC

See deferred procedure call.

drawing functions

A set of functions that a display driver can implement to perform rendering operations. The DDI drawing functions are shown in the following list. These functions perform many kinds of rendering operations, including alpha blends, bit block transfers, rendering lines, color fills, and displaying text.

DrvAlphaBlend
DrvBitBlt
DrvCopyBits
DrvDitherColor
DrvFillPath
DrvGradientFill
DrvLineTo
DrvPlgBlt
DrvRealizeBrush
DrvStretchBlt
DrvStretchBltROP
DrvStrokeAndFillPath
DrvStrokePath
DrvTextOut
DrvTransparentBlt

driver extension

An opaque, system-defined structure, associated with a driver object. The only driver-accessible member of the driver extension is a pointer to the driver's AddDevice routine. Do not confuse driver extensions with driver object extensions.

driver key

See software key.

driver node

A device entry in an INF file's INF Models Section. Each of these entries identifies a device's device identification strings, and references other sections within the INF file that identify the device's installation components, including driver files, service information, device-specific co-installers, registry entries, and so forth.

driver object

A kernel-mode object that represents a driver’s load image and is used by the I/O Manager to locate certain entry points in the driver.

For more information see the topic, Introduction to Driver Objects.

driver object extension

A driver-defined structure containing driver-specific information. Drivers allocate driver object extensions by calling IoAllocateDriverObjectExtension. Do not confuse driver object extensions with driver extensions.

For more information, see DriverEntry's Optional Responsibilities.

driver stack

A chain of drivers that support the operations of a device. For more information see the topic, Layered Driver Architecture.

DS

See distribution system.

DSP

Digital signal processor. An integrated circuit designed for high-speed data manipulations. Used in audio, communications, image manipulation, and other data-acquisition and data-control applications.

DSVD

See digital simultaneous voice and data.

DTE

See data terminal equipment.

DVD

Digital video disc. Digital data storage that encompasses audio, video, and computer data.