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  Table 20-1: Valid Parameter-Passing Mechanisms


  Parameter BY VALUE BY REF BY DESC

  Integer and Real Data

  Variables Yes Yes

                                                                  1
                                                                            Yes
  Constants Yes Local
                                                              copy

                                                                  1

                                                                            Local
                                                                            copy
  Expressions Yes Local
                                                              copy

                                                                  1

                                                                            Local
                                                                            copy
  Elements of a
  nonvirtual array

                                      Yes Yes

                                                                  1
                                                                            Yes
  Virtual
  array elements

                                      Yes Local
                                                              copy

                                                                  1

                                                                            Local
                                                                            copy
  Nonvirtual
  entire array

                                      No Yes Yes

                                                                                1
  Virtual
  entire array

                                      No No No


  Packed Decimal Data

  Variables No Yes

                                                                  1
                                                                            Yes
  Constants No Local
                                                              copy

                                                                  1

                                                                            Local
                                                                            copy
  Expressions No Local
                                                              copy

                                                                  1

                                                                            Local
                                                                            copy
  Nonvirtual
  array elements

                                      No Yes

                                                                  1
                                                                            Yes
  Virtual
  array elements

                                      No Local
                                                              copy

                                                                  1

                                                                            Local
                                                                            copy
  Nonvirtual
  entire arrays

                                      No Yes Yes

                                                                                1
  Virtual
  entire arrays

                                      No No No


  1
    Specifies the default parameter-passing mechanism.

  Parameter BY VALUE BY REF BY DESC


  String Data

  Variables No Yes Yes

                                                                                1
  Constants No Local
                                                              copy

                                                                            Local
                                                                            copy

                                                                                1
  Expressions No Local
                                                              copy

                                                                            Local
                                                                            copy

                                                                                1
  Nonvirtual
  array elements

                                      No Yes Yes

                                                                                1
  Virtual
  array elements

                                      No Local
                                                              copy

                                                                            Local
                                                                            copy

                                                                                1
  Nonvirtual
  entire arrays

                                      No Yes Yes

                                                                                1
  Virtual
  entire arrays

                                      No No No


  Other Parameters

  RECORD variables No Yes

                                                                  1
                                                                            No
  RFA variables No Yes

                                                                  1
                                                                            No


  1
    Specifies the default parameter-passing mechanism.