Hi Bill, (I wrote a Paint and Animation program back when memory and disks were much smaller and slower than they are today.) One wouldn't keep deleted character data in RAM for a long time, consuming valuable resources, but that isn't what is needed for undo. Rather, the "deleted" data can be kept around until the next time the user does something that needs a bunch of memory - at which point, the "deleted" data is "really" deleted so that the user can proceed. For a single-level undo, this is a non-issue, as ANY operation after the delete will quietly toss the old "deleted" data. Even for a multi-level undo, it is easy to cache hundreds of small undo-steps, plus one huge undo-step. In my experience, "Undo" never needs to be a performance OR memory-hog problem. -- ToolmakerSteve