D
 
daemon
A program that runs unattended to perform a service for other programs.
data abstraction
A data type with a private representation and a public set of operations. The C++ language uses the concept of classes to implement data abstraction.
database
(1) A systematized collection of data that can be accessed and operated upon by an information processing system. (2) A collection of information such as tables, views, and indexes.
data definition
(1) A program statement that describes the features or establishes the context of data. (2) A definition that describes a data object, reserves storage for a data object, and can provide an initial value for a data object. A data object appears outside a function or at the beginning of a block statement. IBM.
data identifier
The part of a data access class that is mapped to a database table's key.
data member
A part of an object of class type that is itself an object of user-defined or built-in type. See attribute.
DBCS
See double-byte character set.
debug
To detect, locate, and correct errors in a program.
decimal constant
(1) A numeric data type used in standard arithmetic operations. (2) A number containing any of the digits 0 through 9. IBM.
deck
A line of child windows in a set canvas that is direction-independent. A horizontal deck is equivalent to a row and a vertical deck is equivalent to a column.
declaration
(1) An expression that introduces a name to a program and specifies how the name is to be interpreted. Also called a directive. (2) The mechanism for establishing a language object. (3) In the AIX operating system, a description that makes a defined object available to a function or a block. IBM. (4) In the C language, a description that makes an external object or function available to a function or a block statement. IBM.
declarator
An identifier and optional symbols that declare a single function, object or data type within a declaration. See array declarator, function declarator.
declare
To specify the interpretation that C++ gives to each identifier.
default
The property of a value, attribute, or option that is assumed when no alternative is specified.
default argument
A default value associated with a function parameter. If a call to the function omits this argument, the default value is used. Parameters with default arguments must not appear to the left of parameters without default arguments. See argument.
default class
A class with preprogrammed definitions that can be used for simple implementations.
default clause
In a C or C++ switch statement, the keyword default, followed by a colon and one or more statements. When the conditions of the specified case labels in the switch statement do not hold, the default clause is chosen.
default constructor
(1) A constructor that takes no arguments. (2) A constructor for which all the arguments have default values. See constructor, destructor.
default implementation
One of several possible implementation variants offered as the default for a specific abstract data type.
default initialization
The initial value assigned to a data object by the compiler if no initial value is specified by the programmer. The variables extern and static receive a default initialization of zero, while the default initial value for the auto and register variables is undefined.
default operation class
A class with preprogrammed definitions for all required element and key operations for a particular implementation.
define
In the AIX operating system, to create an entry in the Customized Devices Database and establish the parent device and the connection location. IBM.
define directive
A preprocessor statement that directs the preprocessor to replace an identifier or macro invocation with a specified portion of code.
definition
(1) A data description that reserves storage and may provide an initial value. (2) A declaration that allocates storage, and may initialize a data object or specify the body of a function.
degree
The number of children of a node.
delete
(1) A C++ keyword that identifies a free-storage deallocation operator. (2) A C++ operator used to destroy objects created by operator new.
demangling
The conversion of mangled names back to their original source code names. During C++ compilation, identifiers such as function and static class member names are mangled (encoded) with type and scoping information to ensure type-safe linkage. These mangled names appear in the object file and the final executable file. Demangling (decoding) converts these names back to their original names to make program debugging easier. See mangling.
deque
A queue that can have elements added and removed at both ends. A double-ended queue.
dequeue
An operation that removes the first element of a queue. See enqueue.
derivation
(1) The creation of a new or derived class from an existing base class. (2) The relationship between a class and the classes above or below it in a class hierarchy.
derived class
A class that inherits from a base class. You can add new data members and member functions to the derived class. You can manipulate a derived class object as if it were a base class object. The derived class can override virtual functions of the base class.
destructor
A special member function that is used to destroy, or finalize, objects of its class type. A destructor has no parameters, and no return type is specified. See constructor.
device
A computer peripheral or an object that appears to the application as such. X/Open, I.
dialog box
A window that opens in response to some user-initiated event and indicates the choices available to the user.
digital audio
Audio data that has been converted to digital form.
digital video
Visual data that has been converted to digital form..
digital video device
A full-motion video device that can record or play files (or both) containing digitally stored video.
digraph
Two characters that are used to represent one unavailable character in a source program. Digraphs are read as tokens during the preprocessor stage. See token, trigraph.
diluted array
An array in which elements are deleted by being flagged as deleted, rather than by actually removing them from the array and shifting later elements to the left.
diluted sequence
A sequence implemented using a diluted array.
direct manipulation
A user interface technique that lets a user start application functions by manipulating objects. The user begins an action by moving the mouse pointer over an object and then pressing and holding down the drag mouse button (mouse button 2 is the default for OS/2) while dragging the selected object to a new location. The user then drops the object onto the new location by releasing the mouse button. For this reason, direct manipulation is also known as drag and drop.
directive
A control statement that directs the operation of a feature and is recognized by a preprocessor or other tool. See statement.
directory
A type of file containing the names and controlling information for other files or other directories. IBM.
disassembly
Assembler language for a program module for which the source code is not available. Disassembly is only visible during debugging and can be seen through the Disassembly view or the Disassembly pane of the Source view of the IDE.
display
To direct the output to the user's terminal. If the output is not directed to the terminal, the results are undefined. X/Open.
document component
The basic unit of data exchange in the Compound Document Framework.
do statement
In C and C++, a looping statement that contains the word do followed by a statement (the action), the word while, and an expression in parentheses (the condition). IBM.
double-byte character set (DBCS)
A set of characters in which each character is represented by 2 bytes. Languages such as Japanese, Chinese, and Korean, which contain more symbols than can be represented by 256 code points, require double-byte character sets. Because each character requires 2 bytes, you need hardware and supporting software that are DBCS-enabled to enter, display, and print DBCS characters. Contrast with single-byte character set.
double-precision
Pertaining to the use of two computer words to represent a number in accordance with the required precision. I, ANSI.
doubleword
A contiguous sequence of bits or characters that comprises two computer words and can be addressed as a unit.
drag after
In Compound Document Framework, a target enter event that occurs in a container where its orderedTargetEmphasis or mixedTargetEmphasis attribute is set and the current view is name, text, or details.
drag item
A proxy for the object being manipulated.
drag over
In Compound Document Framework, a target enter event that occurs in a container when its orderedTargetEmphasis attribute is not set and the current view is icon or tree view.
dump
To copy data in a readable format from main or auxiliary storage onto an external medium such as tape, diskette, or printer. IBM.
dynamic
Pertaining to an operation that occurs at the time it is needed rather than at a predetermined or fixed time. IBM.
dynamic binding
Resolution of a call to a virtual member function at run time.
dynamic casting
(C++ only) The conversion of a given expression to a specified type by means of the dynamic_cast operator. This conversion is usually checked and performed at runtime.
dynamic linking
Linking on demand at run time. Contrast with static linking.
dynamic storage
See automatic storage.
 
IBM Copyright 2003