D

DBCS

See double-byte character set.

DC

See device context.

DDE

See dynamic data exchange.

DDE client application

An application that requests a conversation with a dynamic data exchange (DDE) server application, and receives data from the server during the conversation. See also DDE server application.

DDE conversation

The interaction between a dynamic data exchange (DDE) client and a DDE server application.

DDE server application

An application that provides data to a dynamic data exchange (DDE) client application during a DDE conversation. See also DDE client application, DDE conversation.

DDE transaction

An exchange of messages or data between a dynamic data exchange (DDE) client application and a DDE server application. See also DDE client application.

dead key

A key used with another key to create an accented character. A dead key, when pressed, produces no visible character but indicates that the accent mark it represents is to be combined with the character produced by the next letter key pressed. See also key.

deadlock

A bug where the execution of thread A is blocked indefinitely waiting for thread B to perform some action, while thread B is blocked waiting for thread A. For example, two threads on opposite ends of a named pipe can become deadlocked if each thread waits to read data written by the other thread. A single thread can also deadlock itself. See also named pipe, thread.

debugger

An application that enables a developer to observe and correct programming errors by stepping through an application program, examining data, and checking conditions.

debugging

The process of observing and correcting logical and syntactical errors in an application.

debugging event

An event that occurs in a process being debugged that causes the system to notify the debugger. Also, the notification the system sends to the debugger. See also debugger, process.

decorated name

A string created by the compiler during compilation of the function definition or prototype. Functions in C and C++ programs are known internally by their decorated names. A decorated name is sometimes required when you specify a function name to the linker or other tools.

default color palette

An array of RGB values identifying the colors that can be used with a device context by default. The system associates the default color palette with a context whenever an application creates a context for a device that supports color palettes. The default color palette ensures that colors are available for use by an application without requiring additional action by the application.

defragmentation

The process of grouping all the virtual clusters of a file into contiguous logical clusters. Defragmentation is usually done in order to improved disk drive performance. See also logical cluster, virtual cluster.

default window procedure

A system-defined function that provides default processing for messages an application-defined window procedure does not process. See also window procedure.

desktop wallpaper

The pattern created by the bitmap that the desktop window uses to paint the background of the screen.

desktop window

A system-defined window that paints the background of the screen and serves as the base for all windows displayed by all applications.

detached process

A console process that does not have access to the console of its parent process. Typically, a detached process runs in the background, but it can use the AllocConsole function to create a new console if it needs to print a message to the screen or get input from the user. See also console process, parent process.

device

Input sources and output destinations are collectively referred to as devices. Some examples of devices are keyboard (input), monitor (output), printer(output), and disk files, which are input and output devices.

device capabilities

The curve-, line-, polygon-, raster-, and text-drawing capabilities of a display or printer.

device context

Structure that defines a set of graphic objects and their attributes, and the graphic modes that affect output. In addition, the device context (DC) refers to a physical output device—its name, device driver, and other attributes. GDI function call parameters contain a handle to a DC to include the attributes of the specified device. There are four types of DC: display (supports drawing operations on a video display terminal), printer (supports drawing operations on a printer or plotter), memory (supports drawing operations on a bitmap), and information (supports retrieval of device data.) See also graphic modes, graphic objects.

device coordinate space

One of four coordinate spaces used for all graphic device interface (GDI) drawing operations.

device-dependent bitmap

An array of bits that can only be used with a particular display or printer.

device-independent bitmap (DIB)

An array of bits combined with several structures that specify the width and height of the bitmapped image (in pixels), the color format of the device where the image was created, and the resolution of the device used to create that image. See also bitmapped image, pixel.

device interface

Device functionality that a driver exposes to applications or other system components. A driver can expose zero, one, or more than one interface for a particular device. Each device interface is a member of a device interface class.

device interface class

A group of device interfaces with the same functionality. For example, all the joysticks on a system could be members of the joystick device interface class.

An application or a system component can get a list of the devices on the system that support a particular interface by asking for the devices that export an interface of a particular device interface class.

A device interface class is identified by a class GUID. Microsoft defines classes for common device interfaces; IHVs and OEMs can define additional device interface classes.

device type

A class of Media Control Interface (MCI) devices that respond to a common set of commands.

DIB palette

The logical color palette created when a device-independent bitmap (DIB) was created. See also color palette.

DIB pattern-brush

A logical brush created from a device-independent bitmap (DIB). See also device-independent bitmap (DIB), logical brush.

digital differential analyzer (DDA)

An algorithm that determines which pixels on a video display (or dots on a printed page) are part of a line or curve. See also pixel.

directory

An organizational construct supported by most disk-based operating systems. Rather than listing all the files on a volume at once, users can create multiple directories to contain groups of files. Directories can also contain other directories.

disabled window

A window that cannot receive input from keyboard, mouse, or other input device.

disk drive

A physical device that reads from or writes to disks. Disk drives are referenced by letters, typically A for the first floppy-disk drive, B for the second floppy-disk, C for the first fixed-disk drive, D for the second fixed-disk drive, and so on. Each drive on an operating system is assigned a unique letter to distinguish it from other drives.

display context

A special device context that treats each window like a separate screen surface. See also device context, window.

display element

The parts of a window and the display that appear on the system display screen.

dithering

A graphics technique that simulates a color by altering two or more colors in a pattern.

DLL

See dynamic-link library (DLL).

domain

A group of workstations and servers that share a single group name.

double-byte character set (DBCS)

A mapping of characters to their identifying numeric values, in which each value is 2 bytes wide. Double-byte character sets are sometimes used for languages that have more than 256 characters. For example, a double-byte character set is used to encode Japanese (Kanji) characters. See also multibyte character set.

double-click

To press and release a mouse button twice in quick succession.

drag

To move the mouse while holding down a mouse button.

drag-drop

To select one or more files in File Manager, drag them to an open application, and drop them there.

driver service

A service that follows the device driver protocols for Windows NT. These services do not interface with the service control manager. See also service, Win32 service.

drop-down combo box

A combo box, created by using the CBS_DROPDOWN style, containing a drop-down list and a selection field that can be edited by the user.

drop-down list

A list in a combo box that is visible only when it is opened by the user. Combo boxes with the CBS_DROPDOWN and CBS_DROPDOWNLIST styles contain drop-down lists.

drop-down list box

A combo box, created by using the CBS_DROPDOWNLIST style, containing a drop-down list and a selection field that cannot be edited by the user. A drop-down list box can be used in place of a list box when screen space is tight.

due time

The time at which the state of the waitable timer is to be set to signaled. This value is specified when the timer is started. A positive value indicates an absolute time. A negative value indicates a relative time.

dynamic data exchange (DDE)

A form of interprocess communications that uses shared memory to exchange data between applications. Applications can use DDE for one-time data transfers and for ongoing exchanges in applications that send updates to one another as new data becomes available.

dynamic-link library (DLL)

A .DLL file that contains one or more functions compiled, linked, and stored separately from the processes that use them. The operating system maps the DLLs into the process's address space when the process is starting up or while it is running. The process then executes functions in the DLL. See also process.

dynamic priority

A thread priority value used by the scheduler in making scheduling decisions. The value for each thread can never be lower than the thread's base priority, but it can be raised and then lowered to enhance responsiveness to input or other significant events. See also base priority, thread.