SUBROUTINE c_sam(c_f, b, s)  BIND(C, NAME='c_sam')
        USE, INTRINSIC :: iso_c_binding, ONLY : c_char, &
	                c_int, c_null_char  

        INTERFACE
          FUNCTION c_f(x) RESULT(f_res) BIND(C)
          USE, INTRINSIC :: iso_c_binding, ONLY : c_int, c_float
          INTEGER (c_int)   :: f_res
          REAL (c_float)    :: x
          END FUNCTION c_f
        END  INTERFACE

! C requires that the string be one character longer than its Fortran
! equivalent as it needs to be null terminated.
        CHARACTER(KIND=c_char) :: s(8)    ! C requires a stop character
        CHARACTER(len=7)       :: t
        INTEGER (c_int)        :: b
        INTEGER                :: I
        
        CALL sam(c_f,b,t)

        DO I=1,7
           s(I)=t(I:I)
        END DO
	
        s(8)=c_null_char ! End C string

        END SUBROUTINE c_sam

        FUNCTION c_f(x) RESULT (f_res) BIND(C,NAME='c_f')
        USE, INTRINSIC :: iso_c_binding, ONLY : c_int, c_float

        INTEGER (c_int)   :: f_res
        REAL(c_float)     :: x
        INTEGER, EXTERNAL :: f
        f_res=f(x)

        END FUNCTION c_f