Identify books in library

Library book code with Dewey decimal system

The number by which a book is identified

Dewey decimal system - books in a library are arranged by subject. These codes can be committed to memory.

Codes

Reference: https://archive.org/details/decimal18v2dewe

#	Subject
000	Computer science, information and general work
100	Philosophy and psychology
200	Religion
300	Social Sciences
400	Language
500	Science
600	Technology
700	Art and recreation
800	Literature
900	History and geography