D

DAT

Digital audio tape. A consumer recording and playback media for high-quality audio.

data rate

The speed of a data transfer process, normally expressed in bits per second or bytes per second.

DDC

Display data channel. The Plug and Play baseline for monitors. The communications channel between a monitor and the display adapter to which it is connected. This channel provides a method for the monitor to convey its identity to the display adapter.

DDI

Device driver interface.

DDK

Device driver kit.

decompression

To reverse the procedure conducted by compression software, and thereby return compressed data to its original size and condition.

density

The degree of darkness of an image. Also, the percent of screen used in an image.

device

1. Any circuit that performs a specific function, such as a parallel port. 2. For WDM, usually refers to a device object, but also refers to a unit of hardware—for example, an audio adapter—that is detected by Plug and Play.

Device Bay

An industry specification that defines a mechanism for both peripheral devices and system bays that allows adding and upgrading PC peripheral devices without opening the chassis.

device ID

A unique ASCII string created by enumerators to identify a hardware device and used to cross-reference data about the device stored in the registry. Distinguishes each logical device and bus from all others on the system.

device node

The basic data structure for a given device, built by the Configuration Manager. Device nodes are built into memory at system startup for each device and enumerator. Each device node contains information about the device, such as currently assigned resources. The complete hierarchical representation of all device nodes, representing all currently installed devices, is referred to as the hardware tree.

device object

A kernel-mode–only object type used to represent a physical, logical, or virtual device whose driver has been loaded into the system.

devnode

See device node.

DIB

Device-independent bitmap. A file format designed to ensure that bitmap graphics created using one application can be loaded and displayed in another application exactly the way they appeared in the originating application.

digital

A method of signal representation by a set of discrete numerical values, as opposed to a continuously fluctuating current or voltage. Compare with analog.

digital video

A video signal represented by computer-readable binary numbers that describe a finite set of colors and luminance levels. Compare with analog video.

digitization

The process of transforming analog video signal into digital information.

disk I/O controller

Also HDC. A special-purpose chip and circuitry that directs and controls reading from and writing to a computer's disk drive.

DLL

Dynamic link library. API routine that User-mode applications access through ordinary procedure calls. The code for the API routine is not included in the user's executable image. Instead, the operating system automatically modifies the executable image to point to DLL procedures at run time.

DMA

Direct memory access. A method of moving data from a device to memory (or vice versa) without the help of the microprocessor. The system board uses a DMA controller to handle a fixed number of channels, each of which can be used by only one device at a time.

DMI

Desktop Management Interface. A framework created by the DMTF. DMTF specifications define industry-standard interfaces for instrumentation providers and management applications.

DMTF

Desktop Management Task Force.

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, all the ports on an equivalent desktop computer, and AC power.

dongle

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

DPC

Deferred procedure call. Method used in Windows NT/Windows 2000 for event scheduling.

driver

Kernel-mode code used either to control or emulate a hardware device.

driver stack

Device objects that forward IRPs to other device objects. Stacking always occurs from the bottom up and is torn down from the top.

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.

DVD

Optical disk storage that encompasses audio, video, and computer data.

dynamic detection

The process by which a system can detect that a new device has been added or removed from the PC. This process allows the operating system and applications to immediately begin using the added devices or stop using the removed devices without rebooting the system.