By Bill Fane

Analysis of AutoCAD users’ actions suggests that one of the most commonly used functions is undo. It comes in several forms and depths of action. If you’re the impatient type, you can jump ahead to the last two items in this list because they’ll probably account for the majority of your undo actions:

OOPS: The OOPS command un-erases the last set of erased objects, even if other editing or drawing actions have taken place in between. This command has no menu option or Ribbon icon, so you have to type it at the command line.

UNDO: The UNDO command is quite versatile and powerful, with several options. Among other things, you can have it undo a specified number of actions, drop a marker flag, or undo as far back as the marker flag. See the Help facility for more information. You need to type this command on the command line because the only menu option is the typical Windows undo arrow on the Quick Access menu, which undoes only one step and doesn’t prompt for the other options.

U: This command is available in two forms:

  • Type it as a command. It undoes your last action, and you can use it repeatedly to step back through the current editing session. Just press Enter until you back up to the step you need.
  • Enter it as a prompt during a number of other commands, such as Line, PLine, and COpy. In this case, it undoes the last line or polyline segment, or the last objects to be copied — but then the parent command resumes, and you can continue drawing or placing copies.

REDO: This command reverses the last U or UNDO operation. To make REDO work, you must use it immediately after one of these operations. It appears as the typical Windows undo arrow on the Quick Access menu.

DOO-DOO: Or words to that effect. This isn’t a command — instead, it’s what you say when you undo too many steps and then realize, to your horror, that REDO can only redo the last Undo step.

MREDO: This command reverses multiple Undo actions and pretty much eliminates the need for DOO-DOO. It has several advanced options, though the prompts are self-explanatory.

BAK: This isn’t a command — it’s a file type. Whenever you save your work in process, AutoCAD creates a file with the extension .bak that stores your drawing the way it looked immediately after the previous save operation. You can go back to this version by simply using Windows Explorer to rename the BAK file to one with the .dwg extension.

SV$: This one is also a file type. As you work, AutoCAD automatically saves a copy of your drawing every ten minutes and gives it the .sv$ file extension. You can go back to this version by simply using Windows Explorer to rename the SV$ file to one with the .dwg extension. You’ll find your SY$ files in the c:\Users\<login name>\appdata\local\temp folder, but you can use the Files tab of the OPtions command to store them in any location you like.

Undo button: It invokes the UNDO 1 command and option. The Quick Access menu includes an Undo button, just as many Windows applications do.

Redo button: It invokes the MREDO 1 command and option. The Quick Access menu includes a Redo button, just like many Windows applications do.

Don’t you just wish that the real world had Undo and Redo buttons?