Glossary D
- data abstraction
- A style of programming in which you define types to represent objects
in your program, define a set of operations for objects of each type, and
restrict the operations to only this set, making the types abstract. The
Fortran 95/90 modules, derived types, and defined operators, support this
programming paradigm.
- data edit
descriptor
- A repeatable format descriptor that causes the transfer or conversion
of data to or from its internal representation. In FORTRAN-77, this term
was called a field descriptor.
- data entity
- A data object that has a data type. It is the result of the evaluation
of an expression, or the result of the execution of a function reference
(the function result).
- data item
- A unit of data (or value) to be processed. Includes constants, variables,
arrays, character substrings, or records.
- data object
- A constant, variable, or part (subobject) of a constant or variable.
Its type may be specified implicitly or explicitly.
- data type
- The properties and internal representation that characterize data and
functions. Each intrinsic and user-defined data type has a name, a set
of operators, a set of values, and a way to show these values in a program.
The basic intrinsic data types are integer, real, complex, logical, and
character. The data value of an intrinsic data type depends on the value
of the type parameter. See also type
parameter.
- data
type length specifier
- The form *n appended to Compaq Fortran-specific data type names. For
example, in REAL*4, the *4 is the data type length specifier.
- 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
thread.
- declaration
- A statement or series of statements which specify attributes and properties
of named entities, such as specifying the data type of named data objects.
Declaration is a synonym for specification.
- decorated name
- An internal representation of a procedure name or variable name that
contains information about where it is declared; for procedures, the information
includes how it is called. Decorated names are mainly of interest in mixed-language
programming, when calling Fortran routines from other languages.
- default character
- The kind type for character constants if no kind type parameter is
specified. Currently, the only kind type parameter for character constants
is CHARACTER(1), the default character kind.
- default complex
- The kind type for complex constants if no kind type parameter is specified.
The default complex kind is affected by the compiler option specifying
real size. If no compiler option is specified, default complex is COMPLEX(8)
(COMPLEX*8). See also default real.
- default integer
- The kind type for integer constants if no kind type parameter is specified.
The default integer kind is affected by compiler options specifying
integer size. If no compiler option is specified, default integer
is INTEGER(4) (INTEGER*4).
If a command line option affecting integer size has been specified, the
integer has the kind specified, unless it is outside the range of the kind
specified by the option. In this case, the kind type of the integer is
the smallest integer kind which can hold the integer.
- default logical
- The kind type for logical constants if no kind type parameter is specified.
The default logical kind is affected by compiler options specifying
integer size. If no compiler option is specified, default logical is LOGICAL(4)
(LOGICAL*4). See also default integer.
- default real
- The kind type for real constants if no kind type parameter is specified.
The default real kind is affected by the compiler option specifying
real size. If no compiler option is specified, default real is REAL(4) (REAL*4).
If a real constant is encountered that is outside the range for the default,
an error occurs.
- deferred-shape
array
- An array pointer (an array with the POINTER
attribute) or an allocatable array (an array with the
ALLOCATABLE attribute). The size in each dimension
is determined by pointer assignment or when the array is allocated.
The declared bounds are specified by a colon (:).
- definable
- A property of variables. A variable is definable if its value can be
changed by the appearance of its name or designator on the left of an assignment
statement. An example of a variable that is not definable is an allocatable
array that has not been allocated.
- define
- (1) To give a value to a data object during program execution. (2)
To declare derived types and procedures.
- defined assignment
- An assignment statement that is not intrinsic, but is defined by a
subroutine and an interface block. See also derived
type.
- defined operation
- An operation that is not intrinsic, but is defined by a function subprogram
containing a generic interface block with the specifier OPERATOR. See
also interface block.
- denormalized
number
- A computational floating-point result smaller than the lowest value
in the normal range of a data type (the smallest representable normalized
number). You cannot write a constant for a denormalized number.
- derived type
- A data type that is user-defined and not intrinsic. It requires a type
definition to name the type and specify its components (which can be intrinsic
or user-defined types). A structure constructor can be used to specify
a value of derived type. A component of a structure is referenced using
a percent sign (%).
Operations on objects of derived types (structures) must be defined by
a function with an OPERATOR interface. Assignment for derived types can
be defined intrinsically, or be redefined by a subroutine with an ASSIGNMENT
interface. Structures can be used as procedure arguments and function results,
and can appear in input and output lists. Also called a user-defined type.
See also record, the
first definition.
- designator
- A name that references a subobject (part of an object). A designator
is the name of the object followed by a selector that selects the subobject.
For example, B(3) is a designator for an array element. Also called a subobject
designator. See also selector and
subobject.
- dimension
- A range of values for one subscript or index of an array. An array
can have from 1 to 7 dimensions. The number of dimensions is the rank of
the array.
- dimension bounds
- See bounds.
- direct access
- A method for retrieving or storing data in which the data (record)
is identified by the record number, or the position of the record in the
file. The record is accessed directly (nonsequentially); therefore, all
information is equally accessible. Also called random access. Contrast
with sequential access.
- DLL
- See Dynamic Link Library.
- 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. See also
multibyte
character set.
- double-precision
constant
- A processor approximation to the value of a real number that occupies
8 bytes of memory and can assume a positive, negative, or zero value. The
precision is greater than a constant of real (single-precision) type. For
the precise ranges of the double-precision constants, see
Data Representation in
the Programmer's Guide.
See also denormalized number.
- driver program
- On Windows, Tru64 UNIX, and Linux systems, a
program that is the user interface to the language compiler. It accepts command line
options and file names and causes one or more language utilities or system
programs to process each file.
- dummy aliasing
- The sharing of memory locations between dummy (formal) arguments and
other dummy arguments or COMMON variables that are assigned.
- dummy argument
- A variable whose name appears in the parenthesized list following the
procedure name in a FUNCTION statement,
a SUBROUTINE statement, an ENTRY
statement, or a statement function statement. A
dummy argument takes the
value of the corresponding actual argument in the calling program unit
(through argument association). Also called a formal argument.
- dummy array
- A dummy argument that is an array.
- dummy pointer
- A dummy argument that is a pointer.
- dummy procedure
- Is a dummy argument that is specified as a procedure or appears in
a procedure reference. The corresponding actual argument must be a procedure.
- Dynamic
Link Library (DLL)
- A separate source module compiled and linked independently of the applications
that use it. Applications access the DLL through procedure calls. The code
for a DLL is not included in the user's executable image, but the compiler
automatically modifies the executable image to point to DLL procedures
at run time.