ISBN stands for International Standard Book Number - a unique identifier assigned to each edition of every published book and book-like product. The purpose of the ISBN is to establish and identify one title or edition of a title from one specific publisher and is unique to that edition, allowing for more efficient marketing of products by booksellers, libraries, universities, wholesalers and distributors. The ISBN was originally developed as a 10-digit number, which for more than three decades has performed extremely well as a catalog number for books. However, the International ISBN Agency has determined that sometime in the not-too-distant future they will begin to run out of 10-digit numbers for publishers. Accordingly, in January 2007, the ISBN will be redefined from a 10-digit to a 13-digit number. Barcode Professional supports both ISBN-10 as well as ISBN-13 numbers and thus, you can pass to it both type of ISBNs as the value to encode. All ISBN-10 number is automatically converted to ISBN-13 by Barcode Professional. The Components of an ISBN The ISBN number is either 10 or 13 digits long and consists of four or five parts: If 13-digit ISBN, a GS1 Prefix, either 978 or 979 The country of origin or language code The publisher number which is assigned by the national ISBN agency The item number The checksum character which ensures that each ISBN is valid, meaning that the number is correct Notes The different parts can have different lengths and are usually separated by hyphens (-) The "X" that you see at the end of some ISBNs is a Roman numeral, a way of putting the number "10" into a single digit Add-On or Supplement code The Add-On Symbols were designed to encode information supplementary to that in the main bar code symbol on periodicals and paperback books. The Add-On can be composed of 2 or 5 digits only. For ISBN barcodes a Five-digit Add-On is usually used for the Retail Suggested Price. Sample of an ISBN Five-Digit Add-On Barcode Light Margin Indicators - a greater than (>) and/or less than (<) character - are intended to protected the essential light areas to the left and right of the code that the barcode scanner needs to recognize the beginning and end.