books are barcoded. Publisher compliance to the EAN-13 symbology
is almost total. Children's books and specialty products cause some
problems, but the overall standard of barcoding conformance is the
envy of other industries.
combination of industry-wide agreement on item identification and
almost universal compliance to barcode standards makes book handling
an ideal candidate for automated warehouse systems.
distributors are often dismayed to discover that they can't easily
scan a book jacket and extract the ISBN. This article explains why,
and what you can do about it.
ISBN is a 10-character string. The leftmost character is a 'Hemisphere'
number, and the rightmost is a checkdigit. The middle eight digits
are divided to identify the publisher and uniquely identify a title
from that publisher.
description could almost exactly be used to describe a 12-digit
UPC or 13-digit EAN code. However, there are two significant differences:
number of digits assigned to the publisher are not fixed. A
major publisher might be assigned a valuable two-digit number,
reserving six digits for his catalog of titles. A tiny publisher
might be assigned a six-digit number, with only room for a few
titles. It is customary to separate these fields with a dash
in the human-readable version.
checkdigit is calculated MOD-11, which means that it may contain
the alpha character 'X' in addition to the numeric digits. An
ISBN cannot be stored as a number since it may be alphanumeric.
retail barcodes started to become ubiquitous, the publishers wisely
decided not to create their own symbology. They approached the EAN
organization, and cut a deal to map their ISBN numbers onto the
EAN-13 barcode standards.
codes are administered on a national or territorial basis by 'Numbering
Organizations'. Since the publishers already had an international
organization, they were granted a fictitious country, 'Bookland',
and control over their numbers.
'Bookland EANs' start with 978 prefix. The usual nine digits that
represent the company and item numbers are mapped from the first
nine digits of the ISBN. The difficulty is that the checkdigit is
recalculated according to the EAN standards. The tenth ISBN digit
significance is that the ISBN cannot be scanned out of the EAN barcode.
By discarding the EAN prefix, you may extract the first nine digits,
but then you must recalculate the ISBN checkdigit yourself.
Mass Market Books
you look at the back of a hardback or trade paperback, you will
see the human-readable ISBN and, below it, an EAN-13 barcode with
another human-readable number.
mass-market paperbacks often have a UPC on the back. Usually the
price is embedded in this UPC, either in the right-most UPC digits
or in the supplemental barcode. Use of price-point barcodes mean
that the UPC cannot generally be used to identify the book.
books have both UPC and Bookland EAN barcodes on the back. You may
have to check the inside front cover to find the Bookland EAN. If
you are automating your warehouse, you will have to train your staff
to only scan the barcode that starts with '978'.
Converting to ISBN
high-end retail scanning equipment will automatically convert a
Bookland EAN into an ISBN, but RF systems and simple wedge scanners
require you to implement the conversion in software.
algorithm is simple, and can be implemented in about four lines
of BASIC programming. Here's how to recalculate manually:
with a 13-digit EAN barcode, drop the 978 prefix, and save the next
nine digits. You can throw away the final digit - it's just the
your nine-digit number, multiply the first digit of the code by
10, the second digit by 9, the third digit by 8, and so on, adding
the results together (a 'sum of products').
the modulus-11 by dividing the resulting sum-of-products by 11 and
keeping only the remainder. For example, if the sum-of-products
is 174, then taking modulus-11 leaves a remainder of 9 (hint: 15
times 11 is 165). The remainder will always be between 0 and 10.
subtract your remainder from 11. If you end up with 11, use '0',
if you end up with 10, use 'X', otherwise use whatever you got,
glue it to the end of your nine digits, and voila: an ISBN!
well as being useful in the supply chain, this algorithm makes an
interesting math exercise for your child prodigy.