The Undo function — a life-saver.

From “Behavioral issues in the use of interactive systems,” Lance A. Miller and John C. Thomas, International Journal of Man-Machine Studies, Sept. 1977:

A more complex situation, however, occurs … when a user wishes to “undo” the effects of some number of prior commands — as, for example, when a user inadvertently deletes all personal files. Recovery from such situations is handled by most systems by providing “back-up” copies of (all) users’ files, from which a user can get restored the personal files as they were some days previous. While this is perhaps acceptable for catastrophic errors, it would be quite useful to permit users to “take back” at least the immediately preceding command (by issuing some special “undo” command).

Now if they would only invent an Undo button for one’s personal life.

AB — 15 April 2011