10 Main Categories

000 - 099 General Works
Computers, general encyclopedias, newspapers.
100 - 199 Philosophy & Psychology
Great ideas, thinking, dreams, ethics.
200 - 299 Religion
Different religions & beliefs.
300 - 399 Social Sciences
Communities, government, careers, natural resources, schools, transportation, folklore.
400 - 499 Language
Dictionaries, grammar, spelling, with different numbers for different languages.
500 - 599 Pure Sciences
Mathematics, solar system, electricity, rocks, dinosaurs, plants, animals, experiments.
600 - 699 Technology & Applied Sciences
Inventions, human body, farming, cooking, manufacturing different products.
700 - 799 The Arts
Designing buildings, sculpture, drawing, painting, handicrafts, music, theatre, sports.
800 - 899 Literature
Poetry, plays, humour, with different numbers for different languages.
900 - 999 Geography & History
Biographies, flags, ancient history, countries, with different numbers for different continents & countries