Undo key

The Undo Key

The operation of the Undo key depends on the calculator context, but serves largely to recover from the deletion of an entry rather than to undo any arbitrary operation. See The Last X Register in Chapter 2 for details on recalling the entry in line 2 of the display after a numeric function is executed. Press :immediately after using or to recover:

an entry that you deleted

an equation deleted while in equation mode

a program line deleted while in program mode

In addition, you can use Undo to recover the value of a register just cleared using the CLEAR menu. The Undo operation must immediately follow the delete operation; any intervening operations will keep Undo from retrieving the deleted object. In addition to retrieving an entire entry after its deletion, Undo can also be used while editing an entry. Press :while editing to recover:

a digit in an expression that you just deleted using an expression you were editing but cleared using

a character in an equation or program that you just deleted using (while in equation or program mode)

Please note also that the Undo operation is limited by the amount of available memory.