Language Reference

+-------------------------------IBM Extension--------------------------------+

BYTE

Purpose

The BYTE type declaration statement specifies the attributes of objects and functions of type byte. Each scalar object has a length of 1. Initial values can be assigned to objects.

Format

>>-BYTE--+-+----+----------------+--entity_decl_list-----------><
         | '-::-'                |
         '-,--attr_spec_list--::-'
 
 

where:

attr_spec

For detailed information on rules about a particular attribute, refer to the statement of the same name.

intent_spec

is either IN, OUT, or INOUT

::

is the double colon separator. It is required if attributes are specified, = initialization_expr or => NULL() is used.

array_spec

is a list of dimension bounds

entity_decl

>>-a--+------------------+--+------------------------------+--->< '-(--array_spec--)-' '-+-/--initial_value_list--/-+-' +-=--initialization_expr---+ '- => --NULL()-------------'

a

is an object name or function name. array_spec cannot be specified for a function name.

initial_value

provides an initial value for the entity specified by the immediately preceding name

initialization_expr

provides an initial value, by means of an initialization expression, for the entity specified by the immediately preceding name

=> NULL()

provides the initial value for the pointer object

Rules

Within the context of a derived type definition:

• If => appears in a component initialization, the POINTER attribute must appear in the attr_spec_list.
• If = appears in a component initialization, the POINTER attribute cannot appear in the component attr_spec_list.
• The compiler will evaluate initialization_expr within the scoping unit of the type definition.

If => appears for a variable, the object must have the POINTER attribute.

If initialization_expr appears for a variable, the object cannot have the POINTER attribute.

Entities in type declaration statements are constrained by the rules of any attributes specified for the entities, as detailed in the corresponding attribute statements.

The type declaration statement overrides the implicit type rules in effect. You can use a type declaration statement that confirms the type of an intrinsic function. The appearance of a generic or specific intrinsic function name in a type declaration statement does not cause the name to lose its intrinsic property.

An object cannot be initialized in a type declaration statement if it is a dummy argument, an allocatable object, a function result, an object in blank common, an integer pointer, an external name, an intrinsic name, or an automatic object. Nor can an object be initialized if it has the AUTOMATIC attribute. The object may be initialized if it appears in a named common block in a block data program unit or if it appears in a named common block in a module.

In Fortran 95, a pointer can be initialized. Pointers can only be initialized by the use of => NULL().

The specification expression of an array_spec can be a nonconstant expression if the specification expression appears in an interface body or in the specification part of a subprogram. Any object being declared that uses this nonconstant expression and is not a dummy argument or a pointee is called an automatic object.

An attribute cannot be repeated in a given type declaration statement, nor can an entity be explicitly given the same attribute more than once in a scoping unit.

initialization_expr must be specified if the statement contains the PARAMETER attribute. If initialization_expr or NULL() is specified, and the entity you are declaring:

• is a variable, the variable is initially defined.

  +---------------------------------Fortran 95---------------------------------+

  
  
• is a derived type component, the derived type has default initialization.

  +-----------------------------End of Fortran 95------------------------------+

A variable or variable subobject cannot be initialized more than once. If a is a variable, the presence of initialization_expr or NULL() implies that a is a saved object, except for an object in a named common block. The initialization of an object could affect the fundamental storage class of an object.

An array_spec specified in the entity_decl takes precedence over the array_spec in the DIMENSION attribute.

An array function result that does not have the POINTER attribute must have an explicit-shape array specification.

If the entity declared is a function, it must not have an accessible explicit interface unless it is an intrinsic function.

If T or F, defined previously as the name of a constant, appears in a type declaration statement, it is no longer an abbreviated logical constant but the name of the named constant.

Examples

BYTE, DIMENSION(4) :: X=(/1,2,3,4/)

Related Information

• BYTE
• Initialization Expressions
• How Type Is Determined, for details on the implicit typing rules
• Automatic Objects
• Storage Classes for Variables
• DATA, for details on initial values

+-----------------------------End of Fortran 95------------------------------+