The International Standard Book Number (ISBN) is a numeric commercial book identifier which is intended to be unique. Publishers purchase ISBNs from an affiliate of the International ISBN Agency. ISBN is standardised by ISO 2108:2017. ISBN is an example of industry standard code as it applies to commercial books around the world.
Check digits are additional numbers or characters added to codes that a computer uses to verify the number is valid. The intention is to reduce the likelihood of miskeying an item and hitting an alternative live item. More often, a system is devised which a computer can calculate using combination of numbers.
Own product code system: an organisation will use its own product code system. This has the ad-vantage that the organisation can construct a code that is effective and fits with its software and variety of items covered.
The Harmonized Commodity Description and Coding System, also known as the Harmonized System (HS) of tariff nomenclature is an internationally standardized system of names and numbers to classify traded products. It came into effect in 1988 and has since been developed and maintained by the World Customs Organization (WCO) (formerly the Customs Co-operation Council), an independent intergovernmental organization based in Brussels, Belgium, with over 200 member countries.