3 ms·

For some reason, ISBNs having check digits seems really strange to me. I wonder why. I am sure that Australia's smart meter numbering scheme also uses a check d

For some reason, ISBNs having check digits seems really strange to me. I wonder why. I am sure that Australia's smart meter numbering scheme also uses a check digit, but on learning that it that didn't strike me as odd. Maybe the association with books and "old stuff" makes it seem incongruous to me. In general, are check digits common in schemes like these? Is it something you'd do if you expect lots of manual copying, or scanning or other potentially-error-producing conversions?

yencabulator 4y ago
The Finnish identity code, sort of like a US social security number, has had a check digit since 1971 (when the system was digitized). UPC barcodes are from 1974, and have checksums. The ISBN system is from 1970. I'd argue check digits were definitely best current practice in 1970s. Lots of examples at https://en.wikipedia.org/wiki/Check_digit https://en.wikipedia.org/wiki/Check_digit
dx034 4y ago
I get it for a smart meter, you don't want to mix up numbers and provide wrong readings. And they could be read manually and entered into a system, even if they're "smart". But for books, the worst that can happen is that you get the wrong book. Maybe back in the days when people ordered books via phone it was good to have a checksum, but even then the seller would probably read back the name of the book. So I don't really see how it's necessary here.
- bombcar 4y ago
  Lots of things have check digits that may no longer need them. Credit cards have a formula, etc. was important when hand doing things was common and barcode readers were weak perhaps
jcynix 4y ago
Before everything "online" a bookstore would order books from a wholesaler. often via paper. Giving the wrong number would either result in order forms being sent back and force or wrong books being delivered which had to be returned (if possible at all). So having check digits seems like a cleve idea to reduce possible errors resulting in unneeded transactions. And International Bank Account Numbers (IBANs) have two check digits, but at the front, not at the back. And having check digits is important, because it might not be easy to get your money back, if transferred to some unintended account. The IBAN consists of up to 34 alphanumeric characters comprising a country code; two check digits; and a number that includes the domestic bank account number, branch identifier, and potential routing information. The check digits enable a check of the bank account number to confirm its integrity before submitting a transaction. https://en.wikipedia.org/wiki/International_Bank_Account_Number https://en.wikipedia.org/wiki/International_Bank_Account_Num...
tuxlifan 4y ago
I always assumed the check digit was included as safeguard for barcode scanning. Upon a quick reading of the Wikipedia article on EAN-13 it appears that there is some parity to determine the direction of the scan (i.e. upside-down or upright) but the numbers are encoded as-is without any further error correction contrary to e.g. QR codes. Alas, for a definitive answer on the reasoning one might have to buy the relevant ISO standard, if it is even described there. Given that human adults are said to be able to keep 5-9 items in working memory, I would think it prudent to include a check digit for the ISBN when one might be required to manually enter them into search masks, forms, etc. and if only hearing it (e.g. over the phone) might not benefit from the grouping they visually gain from the interspersed dashes. On the topic of correctly copying (manually): whenever I have to be certain to correctly transcribe a long important number or string I would at the end cover up both the source and the transcription, then reveal one character from the end, then the second to last on e.g. the source, verify that the last and the second to last on the transcription matches (in that order!), then uncover the next 2 on the transcription, verify against the source, continue with the source and so on. This helps immensely to discover transposed digits (especially since my mother tongue is German where we swap the tens and ones while speaking (or thinking with the inner voice) a 2-digit number) and not glance over well known digit groups such as zip code or special dates, etc.

yencabulator 4y ago

The Finnish identity code, sort of like a US social security number, has had a check digit since 1971 (when the system was digitized). UPC barcodes are from 1974, and have checksums. The ISBN system is from 1970. I'd argue check digits were definitely best current practice in 1970s. Lots of examples at https://en.wikipedia.org/wiki/Check_digit https://en.wikipedia.org/wiki/Check_digit

dx034 4y ago

I get it for a smart meter, you don't want to mix up numbers and provide wrong readings. And they could be read manually and entered into a system, even if they're "smart". But for books, the worst that can happen is that you get the wrong book. Maybe back in the days when people ordered books via phone it was good to have a checksum, but even then the seller would probably read back the name of the book. So I don't really see how it's necessary here.

bombcar 4y ago
Lots of things have check digits that may no longer need them. Credit cards have a formula, etc. was important when hand doing things was common and barcode readers were weak perhaps

jcynix 4y ago

Before everything "online" a bookstore would order books from a wholesaler. often via paper. Giving the wrong number would either result in order forms being sent back and force or wrong books being delivered which had to be returned (if possible at all). So having check digits seems like a cleve idea to reduce possible errors resulting in unneeded transactions. And International Bank Account Numbers (IBANs) have two check digits, but at the front, not at the back. And having check digits is important, because it might not be easy to get your money back, if transferred to some unintended account. The IBAN consists of up to 34 alphanumeric characters comprising a country code; two check digits; and a number that includes the domestic bank account number, branch identifier, and potential routing information. The check digits enable a check of the bank account number to confirm its integrity before submitting a transaction. https://en.wikipedia.org/wiki/International_Bank_Account_Number https://en.wikipedia.org/wiki/International_Bank_Account_Num...

tuxlifan 4y ago

I always assumed the check digit was included as safeguard for barcode scanning. Upon a quick reading of the Wikipedia article on EAN-13 it appears that there is some parity to determine the direction of the scan (i.e. upside-down or upright) but the numbers are encoded as-is without any further error correction contrary to e.g. QR codes. Alas, for a definitive answer on the reasoning one might have to buy the relevant ISO standard, if it is even described there. Given that human adults are said to be able to keep 5-9 items in working memory, I would think it prudent to include a check digit for the ISBN when one might be required to manually enter them into search masks, forms, etc. and if only hearing it (e.g. over the phone) might not benefit from the grouping they visually gain from the interspersed dashes. On the topic of correctly copying (manually): whenever I have to be certain to correctly transcribe a long important number or string I would at the end cover up both the source and the transcription, then reveal one character from the end, then the second to last on e.g. the source, verify that the last and the second to last on the transcription matches (in that order!), then uncover the next 2 on the transcription, verify against the source, continue with the source and so on. This helps immensely to discover transposed digits (especially since my mother tongue is German where we swap the tens and ones while speaking (or thinking with the inner voice) a 2-digit number) and not glance over well known digit groups such as zip code or special dates, etc.