program data_types
  implicit none ! Force all variables to be explicitly declared.

  logical :: happy = .true. ! A logical can be .true. or .false.
  character (len=18) :: smile = 'Hello World Again!'
  integer, parameter :: wp = 8 ! A parameter can not be changed
  real (kind=wp) :: eight_byte_variable ! System dependent
  complex :: position = (1.0,1.0) ! 1+i

  eight_byte_variable = SQRT(2.0_wp)
! List-directed output (*)
  print *, wp, happy, smile, eight_byte_variable, position
end program data_types