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a Control option or a single step of the UNDO command is available when
the One option is in effect.
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. If no mark is found, Back displays the following
prompt:
This will undo everything. OK? <Y>: Enter y or n or press Enter
Enter y to undo all commands entered in the current session. Enter n to ignore
the Back option.
When you use the Number option to undo multiple actions, UNDO stops if
it encounters a mark.
1092 | Chapter 21 U Commands