Re: Unexpected error
In the old days, an "expected" error was, for example, the user ejecting the floppy disk prematurely. The error was "expected" in the sense that the designer or developer spent some time thinking about what sorts of things could possibly go wrong, and coded against them. The most likely response would have been an error message - hopefully one more meaningful than just a coded number.
An "unexpected" error, on the other hand, is one that they didn't think of. But they still had the good sense to catch it, and display a coded number which could be reported to customer support to aide diagnosing the fault, so that in the next release it could be turned into an "expected" error and handled properly.