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| Command line: undo |
Auto / Control / BEgin / End / Mark / Back / <Number>: Enter an option, enter a positive number, or press ENTER
You can use the options of the UNDO command to undo more than one action at a time. Begin and End define a number of actions as a group, and Mark and Back work together to undo all actions back to a predetermined point.
UNDO displays the command or system variable name on the command line to indicate that you have stepped back before the point where the command was used.
When you use Back or Number to undo multiple actions, AutoCAD LT regenerates or redraws the drawing, if necessary. This occurs at the end of the UNDO command; therefore, entering UNDO 5 will cause at most one regeneration, while U U U U U, could cause as many as five.
UNDO has no effect on the following commands and system variables:
| ABOUT | HELP | QUIT |
| AREA | HIDE | REDRAW |
| ATTEXT | ID | REGEN |
| CONFIG | LIST | RECOVER |
| CVPORT | MSLIDE | RESUME |
| DELAY | NEW | SAVE |
| DIST | OPEN | SHADE |
| DXFOUT | PLOT | TEXTSCR |
| END | PSOUT | |
| GRAPHSCR | QSAVE |
Groups a menu selection as a single command, reversible by a single U command. When the Auto option is on, whenever you choose a menu item AutoCAD LT groups all actions until you exit that item. You can undo the group as if it were one action.
The Auto option is not available if the Control option has turned off or limited UNDO.
ON / OFF <current>: Enter on or off, or press ENTER
Reverses the specified number of preceding actions. The effect is the same as entering U multiple times, but the drawing is not regenerated at each step.
Limits the UNDO command or turns it on or off.
All / None / One <All>: Enter an option or press ENTER
Turns on the full UNDO command.
Turns off the U and UNDO commands and discards any UNDO command information saved earlier in the editing session.
If you attempt to use UNDO while it is turned off, AutoCAD LT offers the Control option, and the following prompt is displayed:
All / None / One <All>:
Limits UNDO to a single action.
The Auto, Begin, and Mark options are not available when None or One is in effect. The main prompt for the UNDO command changes to show that only a Control option or a single step of the UNDO command is possible:
Control / <1>:
The Begin option groups a sequence of actions. All subsequent actions become part of the group until you use the End option to terminate the group. Entering undo begin while a group is already active ends the current group and begins a new group.
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 group is empty. The same applies to U. A mark disappears inside an UNDO group.
The Mark option places a mark in the undo information. The Back option undoes all the work done back to this mark. If you undo one action at a time, AutoCAD LT informs you when you reach the mark.
You can place as many marks as necessary. The Back option undoes work by moving back one mark at a time, removing the mark. If no mark is found, AutoCAD LT displays the following prompt:
This will undo everything. OK? <Y>: Enter y or n
Entering y undoes all commands entered since you last started AutoCAD LT. Entering n causes AutoCAD LT to ignore the Back option.
When you use the Number option to undo multiple actions, UNDO stops if it encounters a mark.
Related Commands: U undoes the most recent action.