We all know that if you type in U and hit ENTER you’ll undo the last command. And if you continue this process you’ll eventually undo back to the beginning of the session of your drawing. The UNDO command provides you a lot of useful tools. Just read the commandline:
Auto: Groups the commands in a macro, such as a menu macro, into a single action, making them reversible by a single U command.
UNDO Auto is not available if the Control option has turned off or limited the UNDO feature.
Control: Limits or turns off UNDO.
Note: The Auto, Begin, and Mark options are not available when None or One is in effect. If you attempt to use UNDO while it is turned off, you are prompted to re-enter a Control option.
- All: Turns on the full UNDO command.
- None: Turns off the U and UNDO commands and discards any UNDO command information saved earlier in the editing session.
- One: Limits UNDO to a single operation.
- Combine: Controls whether multiple, consecutive zoom and pan commands are combined as a single operation for undo and redo operations. Note: Pan and zoom commands that are started from the menu are not combined, and always remain separate actions.
- Layer: Controls whether the layer dialog operations are combined as a single undo operation
· Begin, End: Groups a sequence of actions into a set. After you enter the Begin option, all subsequent actions become part of this set until you use the End option. Entering undo begin while a group is already active ends the current set and begins a new one. UNDO and U treat grouped actions as a single action.
If you enter undo begin without undo end, using the Number option undoes the specified number of commands but does not back up past the begin point. If you want to go back to before the begin point, you must use the End option, even if the set is empty. The same applies to the U command. A mark placed by the Mark option disappears inside an UNDO group.
· Mark, Back: Mark places a mark in the undo information. Back undoes all the work done back to this mark. If you undo one operation at a time, you are informed when you reach the mark. You can place as many marks as necessary. Back moves back one mark at a time, removing the mark. When you use the Number option to undo multiple actions, UNDO stops if it encounters a mark.
This will undo everything. OK? (Displayed if no mark is found during a Back operation) Enter yes to undo all commands entered in the current session. Enter no to ignore the Back option.