The book number is ISBN, and the most intuitive is the bar code and a series of numbers on the back cover of the book. It is distributed to all publishing houses by the General Administration of Press and Publication. The domestic ISBN is still on the second page of the book (generally on the reverse side of the title page) with CIP data, also called copyright page. These two are two indispensable data in the domestic map book. If not, it becomes internal information, and internal information is not allowed to be priced or sold.

7 is the group area code, representing China.

303-05 148 is called publisher number and publication serial number.

1 indicates code checking, and there are certain algorithms (from left to right, 12 digits, odd times 1, even times 3, plus 12 product, divide by 10 to get the remainder, and then subtract this remainder from 10).

I. Calculation method of 10 digit ISBN check code

10 ISBN check code has only one bit, from 0 to 10, 10 is replaced by x ... Its calculation method is:

The first step is to calculate the weighted sum: multiply the first nine digits of ISBN number by 10, 9, 8, 7, 6, 5, 4, 3, 2 respectively, and then add them to get the weighted sum (let the weighted sum be s);

The second step is to calculate the remainder: divide the sum (s) obtained in the first step by 1 1 and take the remainder (let the remainder be m);

The third step is to calculate the check code: subtract the remainder (m) obtained in the second step with 1 1, and the difference is the radix (n) of the check code.

Explain that if the difference n is 10, the check code is the letter x; If the obtained difference n is 1, the check code is the number 0; If the obtained difference value n is another number, the check code is that number.

For example, suppose the first 9 digits of an ISBN number are: 7-309-04547, and the calculation method of its check code is as follows:

Step 1: Calculate the weighted sum: S = 7×10+3× 9+0× 8+9× 7+0× 6+4× 5+5× 4+4× 3+7× 2 = 226.

Step 2: Calculate the remainder (m): m = 226 ÷ 1 1+6.

Step 3: Calculate the check code (n): n = 1 1? 6 = 5

The check code is 5.

Second, the calculation method of 13 digit ISBN check code

The weighting algorithm of the last parity bit of 13 bit ISBN is different from that of 10 bit ISBN. The specific calculation method is as follows:

The first step is to calculate the weighted sum: the odd number of the first 12 bits of ISBN is multiplied by 1, and the even number is multiplied by 3, and then the two are added to get the weighted sum (let the weighted sum be s);

The second step is to calculate the remainder: divide the weighted sum obtained in the first step by 10 and take the remainder (let the remainder be m);

The third step is to calculate the check code: that is, 10 minus the remainder obtained in the second step, and the difference is the radix (n) for calculating the check code.

It shows that if the difference n is 10, the check code is 0.

For example, suppose that the first 12 bits of an ISBN with 13 bits are: 987-7-309-04547.

Step 1: Calculate the weighted sum: S = 9×1+8× 3+7×1+7× 3+3×1+0× 3+9×1+4× 65438.

Step 2: Calculate the remainder (m): m =117 ÷10 The remainder is 7.

Step 3: Calculate the check code (n): n = 10? 7 = 3

So the check code of this book 13 ISBN is 3.