The unlimited undo feature of pcb-rnd allows you to recover from most operations that materially affect you work. Calling <act>pcb_undo</act> without any parameter recovers from the last (non-undo) operation. <arg>ClearList</arg> is used to release the allocated memory. <arg>ClearList</arg> is called whenever a new layout is started or loaded. See also <act>Redo</act>.

Note that undo groups operations by serial number; changes with the same serial number will be undone (or redone) as a group. See <act>Atomic</act>.