penup  -- Command, no inputs.  Abbreviation: pu
     This command tells the turtle to raise its pen from the paper, so that
     it  does  not leave a trace when it moves.  In the case of the display
     turtle, there is no physical pen to move mechanically, but the  effect
     is the same: any forward or back commands after this point do not draw
     a line.  The floor turtle starts with its pen up; the  display  turtle
     starts with its pen down.  Note: the floor turtle will not move on the
     carpet correctly with its pen down; put it on a smooth surface if  you
     want to draw pictures.
