High Quality Content by WIKIPEDIA articles! The Dewey Decimal Classification is a system of library classification made up of ten classes, each divided into ten divisions, each having ten sections. For example, class 600 ("Technology") includes division 630 ("Agriculture and related technologies"), which includes section 636 ("Animal husbandry"). However, 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.