module common
   public :: initial,add,multiply
   integer, parameter, public :: double = 2
   real (kind = double), public :: x,y

contains

subroutine initial()
   print *, "x = ?"
   read *,x
   print *, "y = ?"
   read *,y
end subroutine initial

subroutine add(sum2)
   real (kind = double), intent (in out) :: sum2
   sum2 = x + y
end subroutine add

subroutine multiply(product2)
   real (kind = double), intent (in out) :: product2
   product2 = x*y
end subroutine multiply

end module common

program tasks            ! illustrate use of module and subroutines
! note how variables are passed
   use common

   real (kind = double) :: sum2, product2
   call initial()                 ! initialize variables
   call add(sum2)                 ! add two variables
   call multiply(product2)
   print *, "sum =", sum2, "product =", product2
end program tasks