5 Specification Statements

A specification statement is a nonexecutable statement that declares the attributes of data objects. In Fortran 90, many of the attributes that can be defined in specification statements can also be optionally specified in type declaration statements.

This chapter contains information on the following topics:

• Type declaration statement (Section 5.1)

  Explicitly specifies the properties (for example: data type, rank, and extent) of data objects.

• ALLOCATABLE attribute and statement (Section 5.2)

  Specifies a list of array names that are allocatable (have a deferred-shape).

• AUTOMATIC and STATIC attributes and statements (Section 5.3)

  Control the storage allocation of variables in subprograms.

• COMMON statement (Section 5.4)

  Defines one or more contiguous areas, or blocks, of physical storage (called common blocks).

• DATA statement (Section 5.5)

  Assigns initial values to variables before program execution.

• DIMENSION attribute and statement (Section 5.6)

  Specifies that an object is an array, and defines the shape of the array.

• EQUIVALENCE statement (Section 5.7)

  Specifies that a storage area is shared by two or more objects in a program unit.

• EXTERNAL attribute and statement (Section 5.8)

  Allows external (user-supplied) procedures to be used as arguments to other subprograms.

• IMPLICIT statement (Section 5.9)

  Overrides the implicit data type of names.

• INTENT attribute and statement (Section 5.10)

  Specifies the intended use of a dummy argument.

• INTRINSIC attribute and statement (Section 5.11)

  Allows intrinsic procedures to be used as arguments to subprograms.

• NAMELIST statement (Section 5.12)

  Associates a name with a list of variables. This group name can be referenced in some input/output operations.

• OPTIONAL attribute and statement (Section 5.13)

  Allows a procedure reference to omit arguments.

• PARAMETER attribute and statement (Section 5.14)

  Defines a named constant.

• POINTER attribute and statement (Section 5.15)

  Specifies that an object is a pointer.

• PRIVATE and PUBLIC attributes and statements (Section 5.16)

  Declare the accessibility of entities in a module.

• SAVE attribute and statement (Section 5.17)

  Causes the definition and status of objects to be retained after the subprogram in which they are declared completes execution.

• TARGET attribute and statement (Section 5.18)

  Specifies a pointer target.

• VOLATILE attribute and statement (Section 5.19)

  Prevents optimizations from being performed on specified objects.

For More Information:

• On BLOCK DATA and PROGRAM statements, see Chapter 8.

• On HPF specification directives for Tru64 UNIX systems, see Section 14.2.2.