Re: Newbie question

From: Gene Wirchenko <>
Date: Wed, 22 Jun 2005 13:42:34 -0700
Message-ID: <>

On Wed, 22 Jun 2005 19:54:21 +0100, Paul <> wrote:


>True again, there is no guarantee someone won't type in another valid
>key, but it does knock out the vast majority of mistakes. I guess the
>most common error is to make a mistake in a single character (writing a
>1 as a 7 for example). I think that checksums are specifically designed
>to ensure that changing any one character will invalidate the checksum.
>I could be wrong here but if not, they certainly would take care of most

     Transposition of adjacent characters is also a common error, e.g. "165" for "156". Some checksums catch those errors, too. Two examples are the Canadian Social Insurance Number and the International Standard Book Number.

>And to check that the key is valid (i.e. in the database) and not just
>well-formed, you do need a trip to the server. But hopefully not many
>entries will manage to get to that stage.

     Say what? I hope that all entries get to that stage. That would mean that all of the data entered is well-formed. Now, that that is known, hit the server to see if the entry is valid.


Gene Wirchenko Received on Wed Jun 22 2005 - 22:42:34 CEST

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