EXTERNAL Statement

Description

The EXTERNAL statement declares external procedures. Specifying a procedure name as EXTERNAL permits the procedure name to be used as an actual argument.

Syntax
 

     EXTERNAL [::] external-name-list
 Where:
 

     

         external-name-list is a comma-separated list of
         

             external procedures, dummy procedures, or block data program units
     

 
 

Remarks

If an intrinsic procedure name appears in an EXTERNAL statement, the intrinsic procedure is not available in the scoping unit and the name is that of an external procedure.

A name can appear only once in all of the EXTERNAL statements in a scoping unit.

If the external procedure is a block data subprogram, the inclusion of the block data in the program is required.

Example
       program main
         external sub1            ! external statement
         integer,external :: fun1 ! external attribute
         call bill(sub1,fun1)
       end program
       subroutine bill(proc,fun)
         integer :: fun,i
         i=fun()
         call proc(i)
       end subroutine
       subroutine sub1(i)
         integer :: i
         write(*,*) i
       end subroutine
       function fun1()
         integer :: fun1
         fun1=1
       end function