Language Reference

EXTERNAL

Purpose

The EXTERNAL attribute specifies that a name represents an external procedure, a dummy procedure, or a block data program unit. A procedure name with the EXTERNAL attribute can be used as an actual argument.

Format

>>-EXTERNAL--+-----+--name_list--------------------------------><
             '- ::-'
 
 

name

is the name of an external procedure, dummy procedure, or BLOCK DATA program unit

Rules

If an external procedure name or dummy argument name is used as an actual argument, it must be declared with the EXTERNAL attribute or by an interface block in the scoping unit, but may not appear in both.

If an intrinsic procedure name is specified with the EXTERNAL attribute in a scoping unit, the name becomes the name of a user-defined external procedure. Therefore, you cannot invoke that intrinsic procedure by that name from that scoping unit.

You can specify a name to have the EXTERNAL attribute appear only once in a scoping unit.

A name in an EXTERNAL statement must not also be specified as a specific procedure name in an interface block in the scoping unit.

Examples

      PROGRAM MAIN
        EXTERNAL AAA
        CALL SUB(AAA)         ! Procedure AAA is passed to SUB
      END
 
      SUBROUTINE SUB(ARG)
        CALL ARG()            ! This results in a call to AAA
      END SUBROUTINE

Related Information

• Procedures as Dummy Arguments
• Item 4 under Appendix A, Compatibility Across Standards