Aucb.379
fa.editor-p
utzoo!decvax!ucbvax!CAD:ARPAVAX:C70:editor-people
Fri Feb  5 16:18:45 1982
Undo
>From ZIMMER@DEC-MARLBORO Fri Feb  5 16:12:46 1982
The prototype version of Etude allowed a single-step undo.  Everything could
be undone except for file manipulation operations.  The underlying
implementation could have handled a multiple-step undo, but the user
interface didn't handle it.

Single-step undo isn't sufficient for good error recovery; see the example
of "edit" in Bravo mentioned a few messages ago.  The questions
about how to do multiple-step undo are good.  We really need some
experimental evidence to guide us in this area.

Undo is handy not only as an error-correction aid, but also as a
way to encourage people to experiment with a system.  When someone asks
"What does this do?" you can say "Try it; if you don't like it you can
always undo it."  This approach was used in Etude's tutorial.

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