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# P- ISSN: 2348-795X WHAT DO X INDICATE IN ISSN? An ISSN is composed of eight digits: the arabic numerals 0 to 9, except that in the case of the last digit, which is a check digit, the upper case X can appear. The purpose of the check digit is to guard against errors caused by the incorrect transcription of the ISSN. The method of determining the check digit for the ISSN is the modulus 11 basis, using the weighting factors 8 to 2. In the case of the ISSN, the Roman numeral X is used where the check digit calculation results in a remainder of 10.

The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers. As an integer number, it can be represented by the first seven digits. The last code digit, which may be 0-9 or an X, is a check digit.

You can check ISSN at this Link on Entering First Seven Digits

The ISSN Calculator

This website provides a facility for computing the eighth digit of an ISSN number, given the first seven numbers. ISSN stands for 'International Standard Serial Number', and is a number that is assigned to a serial publication such as an online journal. The format for an ISSN is given by:

xxxx-xxxy

, where x is a number in the range 0-9, and y is either a number in the range 0-9 or the letter X. The value of the digit y is called the check digit. The sole function of the ISSN Calculator available in this site is to compute this value. On applying for an ISSN number, an applicant is issued with a unique sequence of seven numbers. It is then left to the applicant to compute the check digit.

### Calculating the check digit

Excerpted from the ISSN Manual, a publication of the ISSN International Network

The purpose of a check digit is to guard against errors caused by the incorrect transcription of an ISSN. The modulus 11 basis using the weighting factors 8 to 2 for calculating the check digit is one of the most efficient systems for detecting transcription errors.

The procedure for calculating the check digit, which may be carried out automatically in a computer, is as follows:

1. Take the first seven digits of the ISSN (the check digit is the eighth and last digit): 0 3 1 7 8 4 7
2. Take the weighting factors associated with each digit : 8 7 6 5 4 3 2
3. Multiply each digit in turn by its weighting factor: 0 21 6 35 32 12 14
4. Add these numbers together: 0+21+6+35+32+12+14 = 120
5. Divide this sum by the modulus 11: 120:11 =10 remainder 10
6. Substract the remainder from 11: 11-10 = 1
7. Add the remainder, which is the check digit, to the extreme right (low order) position of the base number of the ISSN: 0317-8471

If the remainder is 10, substitute an upper case X in the check digit position. If there is no remainder, put a zero in the check digit position.

It should be noted that the check digit is an essential and inseparable part of the ISSN.