[W/K] :: copying garbage collection

  copying garbage collection
       
          A garbage collection method where memory is divided into two
          equal halves, known as the "from space" and "to space".
          Garbage collection copies active cells from the from space to
          the to space and leaves behind an invisible pointer (an
          "indirection") from the old position to the new copy.  Once
          all active cells have been copied in one direction, the spaces
          are swapped and the process repeated in the opposite
          direction.