ISBN is the book number, the most intuitive bar code on the back cover of the book and the string of numbers. It is distributed to all publishing houses by the General Administration of Press and Publication. ISBN is prefixed with 978, and China is assigned to use the ISBN number starting with 7, so the barcodes on books published by Chinese publishing houses are all 978-7. The second group number is the publishing house code, which is assigned by the ISBN center of the country or region to which it belongs, and the allowable value range is 2-5 digits. The bigger the publishing house, the more books it publishes, and the smaller the number. The third group is the book sequence code, which is given by the publishers themselves. The book sequence number of each publisher is fixed (the number 9 minus the number of digits occupied by the group number and the publisher code is the number of digits of the book sequence code). The shortest one and the longest six. The bigger the publishing house, the more books published and the longer the serial number.

The fourth group is the computer check code, with only one digit, from 0 to 9.