module m
  implicit none
contains
  real function twice(x)
      real, intent(in) :: x
      twice = 2 * x
  end

  subroutine sub(x, y)
      implicit none
      real, intent(in) :: x
      real, intent(out) :: y
      y = 2 * x + 4.5
  end
end

program main
use m
implicit none
real :: x, y
x = 10.0
call sub(x, y)
print *, y
print *, twice(y)
end

module m
    implicit none
contains
    real function twice(x)
        real, intent(in) :: x
        twice = 2 * x
    end function twice

    subroutine sub(x, y)
        implicit none
        real, intent(in) :: x
        real, intent(out) :: y
        y = 2 * x + 4.5
    end subroutine sub
end module m

program main
    use m
    implicit none
    real :: x, y
    x = 10.0
    call sub(x, y)
    print *, y
    print *, twice(y)
end program main