- D
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- 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.
- 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 initioal value for a data
object. A data object appears outside a function or at
the beginning of a block statement. IBM.
- data member
- The smallest possible piece of complete data. Elements
are composed of data members.
- data object
- Anything that exists in storage and on which operations
can be performed. Examples include files, programs, and
arrays.
- data structure
- The internal data representation of an implementation.
- data type
- (1) The mathematical properties and internal
representation of data and functions. The four basic
types are integer, real, complex, and logical. IBM.
(2) An attribute used for defining data as numeric or
character. IBM.
- 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. Synonymous
with 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
- In the AIX operating system, an identifier and optional
symbols that describe the data type. See array declarator, function declarator.
- declare
- To specify the interpretation that C++ gives to each
identifier.
- default
- A value, attribute, or option that is assumed when no
alternative is specified by the programmer.
- default argument
- An argument that is declared with a default value in a
function prototype or declaration. If a call to the
function omits this argument, the default value is used.
Arguments with default values must be the trailing
arguments in a function prototype argument list. 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
- In C++, a special member function that has the same name
as its class, preceded by a tilde (~). It "cleans
up" after an object of that class. For example, a
destructor frees storage that was allocated when the
object was created. A destructor has no arguments, 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.
- digital audio
- Audio data that has been converted to digital form.
- digital video
- Material that can be seen and 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.
- 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
- (1) A user interface technique whereby the user initiates
application functions by manipulating the objects,
represented by icons, on the desktop. Also known as
drag-and-drop manipulation. (2) In the Windows operating
system, a unit of data. The unit is often part of a task
that is shared among users.
- 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.
- 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.
- DLL
- See dynamic link library.
- 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
- 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
- A target enter event that occurs in a container where 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
- An intelligent mechanism for obtaining the correct
pointer to a base class.
- dynamic linking
- Linking on demand at run time. Contrast with static linking.
- dynamic link
library (DLL)
- On OS/2 and Windows operating systems, a file containing
executable code and data bound to a program at load time
or run time, rather than during linking. The code and
data in a dynamic link library can be shared by several
applications simultaneously. IBM. In
VisualAge application development, a dynamic link library
must have the file extension .dll. See shared library. Contrast
with static library.
- dynamic storage
- See automatic storage.
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