function save()
  if selected_screen ~= default_screen then
    file = io.open("screens/"..screen_id..".scr", "w")
    file:write(selected_screen)
    file:close()
  end
end

function load()
  file = io.open("screens/"..screen_id..".scr", "r")
  if file then
    selected_screen = file:read()
    file:close()
  else
    selected_screen = default_screen
  end
end