An aggregate reference resolves into a reference to a structured
 data item (a record structure or substructure).  For example:

 Data Declarations:

    STRUCTURE /STRA/
        INTEGER  INTFLD, INTFLDARY (10)
    END STRUCTURE
      . . .
    STRUCTURE /STRB/
        CHARACTER*20  CHARFLD
        INTEGER  INTFLD, INTFLDARY (10)
        STRUCTURE STRUCFLD
            COMPLEX  CPXFLD, CPXFLDARY (10)
        END STRUCTURE
        RECORD  /STRA/  RECFLD, RECFLDARY (10)
    END STRUCTURE
      . . .
    RECORD  /STRB/  REC, RECARY (10)

 Reference Examples:

    REC --- A record name
    RECARY(1) --- A record array reference
    REC.RECFLD --- A reference to a substructure
    REC.RECFLDARY(1) --- A reference to a substructure array element
    RECARY(1).RECFLD --- A reference to a substructure in a record
      array element
    RECARY(1).RECFLDARY(1) --- A reference to a substructure array
      element in a record array

 An array is a group of contiguous storage locations associated with
 a single symbolic name, the array name.  The individual storage
 locations, called array elements, are referred to by a subscript
 appended to the array name.  An array can have from 1 to 7
 dimensions.  The Fortran statements that establish arrays are:
 type declaration statements, the DIMENSION statement, and the
 COMMON statement.

 The data type of an array is specified in the same way as the data
 type of a variable; either implicitly by the first letter of the
 name or explicitly by a type declaration statement.

• Declarators
• Subscripts

 An array name reference resolves into the name of an array with no
 subscripts after the array name.  For example:

 Data Declarations:

    INTEGER INT, INTARY (10)
      . . .
    STRUCTURE /STRA/
        INTEGER  INTFLD, INTFLDARY (10)
    END STRUCTURE
      . . .
    STRUCTURE /STRB/
        CHARACTER*20  CHARFLD
        INTEGER  INTFLD, INTFLDARY (10)
        STRUCTURE STRUCFLD
            COMPLEX  CPXFLD, CPXFLDARY (10)
        END STRUCTURE
        RECORD  /STRA/  RECFLD, RECFLDARY (10)
    END STRUCTURE
      . . .
    RECORD  /STRB/  REC, RECARY (10)

 Reference Examples:

    INTARY --- Numeric or character array
    RECARY --- Array of records
    REC.INTFLDARY --- Numeric or character array field of a record
    REC.RECFLDARY --- Array of substructures within a record
    RECARY(1).INTFLDARY --- Numeric or character array field of a
      record array element
    RECARY(1).RECFLDARY --- Array of substructures within a record
      array element

 A constant is a fixed value.  The value of a constant can be a
 numeric value, a logical value, or a character string.  There are
 seven types of constants:  integer, real, complex, bit, logical,
 character, and Hollerith.  Bit and Hollerith constants have no data
 type; they assume a data type that conforms to the context in which
 they are used.

• Bit
• Character
• Complex
• Hollerith
• Integer
• Logical
• REAL
• DOUBLE_PRECISION
• REAL_16

 An expression represents a single value.  An expression can consist
 of a single constant, variable, record element, array element, or
 function reference; or combinations of these data items plus
 certain other elements, called operators.  Operators specify
 computations to be performed on the values of the data items and a
 single result is obtained.

 Expressions are classified as arithmetic, character, relational, or
 logical.  Arithmetic expressions produce numeric values; character
 expressions produce character values; and relational and logical
 expressions produce logical values.

 The data components of an expression must be compatible and must be
 joined by compatible operators.  Expressions are evaluated one
 operator at a time according to the rules of precedence.  The
 ranking assigned to each data type is as follows:

   Data Type                    Ranking
   ---------                    -------
   BYTE                          1 (lowest)
   LOGICAL*1                     1
   LOGICAL*2                     2
   LOGICAL*4                     3
   LOGICAL*8 (AXP only)          4
   INTEGER*1                     5
   INTEGER*2                     6
   INTEGER*4                     7
   INTEGER*8 (AXP only)          8
   REAL (REAL*4)                 9
   DOUBLE PRECISION (REAL*8)    10
   COMPLEX (COMPLEX*8)          11
   DOUBLE COMPLEX (COMPLEX*16)  12 (highest)

• Arithmetic
• Character
• Logical
• Relational

 A record is a named data entity, consisting of one or more fields,
 which you can use when you need to declare and operate on
 multi-field data structures in your programs.

 To create a record, you must have a structure declaration (to
 describe the fields in the record) and a RECORD statement to
 establish the record in memory.

• Examples
• Field_References

 A scalar reference is a scalar variable, scalar record field, array
 element, constant, character substring, or expression that resolves
 into a single, typed data item.  For example:

 Data Declarations:

    INTEGER INT, INTARY (10)
      . . .
    STRUCTURE /STRA/
        INTEGER  INTFLD, INTFLDARY (10)
    END STRUCTURE
      . . .
    STRUCTURE /STRB/
        CHARACTER*20  CHARFLD
        INTEGER  INTFLD, INTFLDARY (10)
        STRUCTURE STRUCFLD
            COMPLEX  CPXFLD, CPXFLDARY (10)
        END STRUCTURE
        RECORD  /STRA/  RECFLD, RECFLDARY (10)
    END STRUCTURE
      . . .
    RECORD  /STRB/  REC, RECARY (10)

 Reference Examples:

    INT --- Numeric variable
    INTARY(1) --- Numeric array element
    REC.INTFLD --- Numeric field
    REC.INTFLDARY(1) --- Numeric element of an array field
    CHARVAR(5:10) --- Substring expression of a character variable
    REC.CHARFLD(5:10) --- Substring expression of a character field

 Note:  A scalar memory reference is the same as a scalar reference,
 excluding constants, character substrings, and expressions.

 A character substring is a contiguous segment of a character
 variable, character array element, or character field reference.
 It has one of the following forms:

    v([e1]:[e2])  OR  a(s[,s]...)([e1]:[e2]) 

    v    Is a character variable name
    a    Is a character array name
    s    Is a subscript expression
    e1   Is a numeric expression specifying the leftmost
         character position of the substring
    e2   Is a numeric expression specifying the rightmost
         character position of the substring
 NOTE:
   1 .LE. e1 .LE. e2 .LE. length-of-v must hold true

 The Fortran data types are as follows:

  o  Integer - a whole number

  o  REAL (REAL*4) - a single-precision floating point number (a
     whole number or a decimal fraction or a combination)

  o  DOUBLE PRECISION (REAL*8) - a double-precision floating point
     number (like REAL*4, but with twice the degree of accuracy in
     its representation)

  o  COMPLEX (COMPLEX*8) - a pair of REAL*4 values representing a
     complex number (the first part of the number is the real part,
     the second is the imaginary part)

  o  COMPLEX*16 (DOUBLE COMPLEX) - like complex, but with twice the
     degree of accuracy in its representation (its real or imaginary
     part must be a REAL*8)

  o  Logical - a logical value, .TRUE.  or .FALSE.

  o  Character - a sequence of characters

  o  BYTE - equivalent to INTEGER*1

• Character
• COMPLEX
• Integer
• Logical
• REAL

 A variable is represented by a symbolic name which is associated
 with a storage location.  The value of the variable is the value
 currently stored in that location; the value can be changed by
 assigning a new value to the variable.

 Variables, like constants, are classified by data type.  When data
 of any type is assigned to a variable, it is converted, if
 necessary, to the data type of the variable.  You can establish the
 data type of a variable by type declaration statements, IMPLICIT
 statements, or predefined typing rules.

• Implication
• Specification