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This is a collection of questions that pop up repeatedly.

Why doesn't 0.3-(3*0.1) evaluate to zero? The short answer is that the computer works with finite precision and that it uses base-2 numbers in which 0.1 is an infinitely repeating fraction. The long version is available as a technical note.

Why does Gnumeric exit when the last window is closed? Basically, we — the developers — like it that way. It is a common behaviour for many applications: you see it in most, if not all, browsers for example. Also, since Gnumeric supports having multiple independent copies of the program running, keeping a blank window around for every window closed would produce some really strange behaviour.