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D

DACL
See discretionary access control list.
DAT
Digital audio tape. A consumer recording and playback media for high-quality audio.
data circuit equipment
See data circuit-terminating equipment.
data circuit-terminating equipment (DCE)
Data circuit-terminating equipment is required to attach data terminal equipment (DTE) to a network or serial line. Data circuit-terminating equipment (DCE) includes devices such as modems and ISDN terminal adapters.
data communications equipment
See data circuit-terminating equipment.
data flow
An arbitrary method of defining a class of connection between devices. Facilitates identification of pin pairs that present compatible flow values, and therefore are more likely to be able to establish a connection.

For more information see the topic, KSPROPERTY_PIN_COMMUNICATION.

data sink pin
A pin on a filter that consumes binary media (stream) data from the data flow. A data input pin. A sink may be a window on screen, a sound card, a file, and so on.
data source pin
A pin on a filter that produces binary media (stream) data. A data output pin. A source is a provider of multimedia information. Examples of a source include a USB Webcam and a 1394 Digital Video Camcorder.
data terminal equipment (DTE)
Includes devices that are the source or destination of data. These devices are connected by data circuit-terminating equipment. Data terminal equipment includes devices such as PCs and printers.
DCB
See directory control block.
DCE
See data circuit-terminating equipment.
DDC
Display data channel. A standard that defines a 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.
deadlock
A run-time error condition that occurs when two threads of execution are blocked, each waiting to acquire a resource that the other holds, and both unable to continue running.
decorated INF section
An INF file section whose name contains a suffix ("decoration") that identifies a particular platform and/or operating system. For example, [SourceDisksNames.x86] and [aha154x.ntx86] are examples of decorated section names. Decorated sections contain installation information that is only relevant to the platform and/or operating system specified by the suffix.

For more information see the topic, Creating INF Files for Multiple Platforms and Operating Systems.

deferred procedure call (DPC)
A queued call to a kernel-mode function that will usually be executed at a later time. DPCs are used by drivers to schedule I/O operations that do not have to take place in an ISR at a high IRQL, and can instead be safely postponed until the processor IRQL has been lowered.

For more information, see the topic, DPC Objects and DPCs.

DPCs can also be used with timers. For more information, see the topic, Timer Objects and DPCs.

design space
See notional space.
despooling
The conversion of spooled device-independent records into device-specific records.
device
A device object, or hardware, or software functionality such as a codec.
device class
Either a device setup class or a device interface class.
device co-installer
See co-installer.
device context (DC)
A structure that defines a set of graphic objects and their associated attributes, and the graphic modes that affect output. The graphic objects include a pen for line drawing, a brush for painting and filling, a bitmap for copying or scrolling parts of the screen, a palette for defining the set of available colors, a region for clipping and other operations, and a path for painting and drawing operations.

Conceptually, a device context is a link between a Windows-based application, a device driver, and an output device such as a display, printer, or plotter.

device driver interface (DDI)
A set of functions that are implemented by the operating system for use by drivers.
device ID
A vendor-defined device identification string that is the most specific ID that Setup uses to match a device to an INF file.

For more information see the topic, Device Identification Strings.

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

device installation application
A vendor-supplied, user-mode application that installs devices, if the driver package replaces Microsoft-supplied drivers and INF files or if the driver package includes vendor-supplied device-specific applications. For more information, see Writing a Device Installation Application.
device instance
A physical piece of hardware. For example, if Company ABC manufactures a CD-ROM drive with a model name of XYZ, and if a particular system includes two of these drives, then there are two instances of device model XYZ.
device instance ID
A system-supplied device identification string that uniquely identifies an instance of a device in the system. This string consists of a device ID and an additional, instance-specific instance ID.

For more information see the topic, Device Identification Strings.

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

device interface
Device functionality that a driver exposes to applications or other system components. Each device interface is a member of a system-defined or vendor-defined device interface class.

A driver can expose instances of zero, one, or more than one device interface class for a device. For example, a device could have a joystick and a keypad, and the device's driver stack could expose instances of three interface classes for the device: a joystick, a keypad, and a combined joystick/keypad.

device interrupt request level (DIRQL)
The IRQL at which a given device interrupts.

See also IRQL and IDT.

device key
See hardware key.
device management
The exchange of requests and responses that control and configure the operational state of a device. Device management requires the use of a Communication Class interface.
device node
See devnode.
device object
A kernel-mode object, defined by the I/O Manager, that represents a physical, logical, or virtual device. Each driver calls IoCreateDevice to create and initialize a device object for each physical, logical, or virtual device that the driver services. PnP drivers create three kinds of device objects: bus drivers create PDOs, function drivers create FDOs, and filter drivers create filter DOs. A device is "visible" to end users as a named file object, and to user-mode code (protected subsystems) through a named device interface.

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

See also device extension, devnode, and driver object.

device palette
See palette.
device power policy owner
The driver for a device that controls its power policy, determining when it sleeps and when it wakes. Typically, the function driver for the device assumes this role, requesting power IRPs to put the device to sleep or to wake it up.
device queue object
A kernel-mode-only, kernel-defined control object type used to queue I/O requests for subsequent processing. A device queue object has an associated executive spin lock and a state (Busy or Not Busy).

An I/O request, called a "queue entry," is not actually placed in the queue unless the state of the device queue object is already Busy:

For more information see the topic, Driver-Managed IRP Queues.

device space
The coordinate space that measures 227 units in height by 227 units in width, in which the x coordinate increases toward the right and the y coordinate increases downward. The only transformation allowed in device space is translation, which ensures that the origin in device space maps to the proper location on the physical device (that is, in physical device space).

See also design space.

device stack
A chain of attached device objects that represent the drivers for a device.

For PnP devices, the device object at the bottom of the device stack is the PDO created by the underlying bus driver. Typically, there is an FDO somewhere in the chain above the PDO. The FDO is created by the function driver for the device. Filter DOs are attached above and below the FDO.

The PDO is created by the underlying bus driver when it enumerates the device. The FDO and filter DOs are created by their respective function and filter drivers and are attached to the stack by those drivers' AddDevice routines.

device-dependent bitmap (DDB)
A data structure that describes a bit image by specifying the width and height of a rectangular region in pixels; the width of the array that maps entries from the device palette to pixels; and the device’s color format in terms of color planes and bits per pixel. A DDB is device-managed, as opposed to being engine-managed.

See device-independent bitmap.

device-independent bitmap (DIB)
Information on the bitmap is stored in a data structure containing information such as color format, resolution, and color palette for the device on which the image appears; an array of bits that maps RGB triplets to pixels; and a data-compression identifier that indicates which, if any, data compression scheme was used to reduce the size of the array of bits. A DIB is a GDI bitmap that can be rendered accurately on different devices because it contains a color table that can be read by the rendering device driver. These are standard format bitmaps created and supported by GDI through EngCreateBitmap. A DIB is engine-managed, as opposed to being device-managed.

See device-dependent bitmap.

device-managed surface
A surface managed by a particular output device, rather than by the Graphics Engine (kernel-mode GDI). There are two types of device-managed surfaces: standard-format bitmaps, and nonstandard-format surfaces.

A standard-format bitmap can be either opaque or nonopaque. These terms indicate whether GDI has information about the location and format of the bitmap. For a standard-format bitmap that is opaque, the display driver must handle all rendering tasks done on the surface. For a standard-format bitmap that is nonopaque, the display driver handles some rendering tasks, and can refer others back to GDI.

A display driver calls on GDI to create a nonstandard-format surface. After creating the surface, GDI returns a surface handle to the display driver, which must carry out all subsequent operations pertaining to the surface. One type of nonstandard-format surface is the device-dependent bitmap (DDB), which is supported to allow drivers such as the VGA driver perform faster bitmap-to-screen block transfers.

For more information see the topic, Surface Types.

devnode
An internal structure that represents a device on the system.

There is a devnode for each device on a machine and the devnodes are organized into a hierarchical device tree. The PnP Manager creates a devnode for a device when the device is configured.

A devnode contains the device stack (the device objects for the device's drivers) and information about the device such as whether the device has been started and which drivers have registered for notification on the device.

digital simultaneous voice and data (DSVD)
A signaling method that mixes data and digitized voice.
direct memory access (DMA)
A method of transferring data between a device and main memory without intervention by the CPU. DMA is handled by the device itself (bus-mastering or first-party DMA) or by a DMA controller chip in the system (slave or third-party DMA).
directory control block (DCB)
An internal NT file system structure in which a file system maintains state for an open instance of a directory file.
directory file
A file that points to or lists a set of named file objects.

Note that on-disk directory files are represented in the kernel as file objects, not as object directory objects.

See also file object and object directory object.

directory object
See object directory object.
DirectX
A set of multimedia APIs that Microsoft provides.
Dirid
Directory identifier. A numeric identifier used within INF files to represent a disk directory. For more information, see Using Dirids.
DIRQL
See device interrupt request level.
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