ComputerCraft Move Turtle

while true do
  local sEvent, param = os.pullEvent("key")
  if sEvent == "key" then
      if param == 28 then
          print("Stopped moving")
          break
      elseif param == 17 then
        turtle.up()
      elseif param == 31 then
        turtle.down()
      elseif param == 200 then
        turtle.forward()
      elseif param == 203 then
        turtle.turnLeft()
      elseif param == 205 then
        turtle.turnRight()
      elseif param == 208 then
        turtle.back()
      end
  end
end