The Dewey Decimal Classification is a system of library classification made up of ten classes, each divided into ten divisions, each having ten sections.[1] For example, class 600 ("Technology") includes division 630 ("Agriculture and related technologies"), which includes section 636 ("Animal husbandry").[1] Practically, there are only 99 of 100 divisions and 908 of 999 sections in total, as some are no longer in use or have not been assigned.