The Hitch Hiker's Guide to the Galaxy, Earth Edition - 910.03

You see the young, somewhat dishevelled man looking over the same shelf for the 15th time.
Finally, what looks like help in the form of an eternally bored girl with an unlimited amount
of books on a cart is spotted. The young man approaches. 'Excuse me, miss,' he says,
'but I've been looking for a book on cheese for what seems like hours now. It should be
right here, between these biographies of Cheektowaga and Anton Chekhov... right?' The
girl turns to him slowly, stares at him for what seems like years, and then
bangs her head against the wall.

Over and over again.

The Dewey decimal system is a method of classification used in libraries. It is usually used for books, but can also be used with non-fiction videos, tapes, CDs, etc. This way, instead of having to go to the trouble of looking for the subject alphabetically as a perfectly sane person would do, one must find the subject either by looking in a card catalogue (which, oddly enough, is in alphabetical order) or using the library computer catalogue, taking down the number provided, and looking for that instead.

The Dewey decimal system was thought up in 1874 by Melvil Dewey, an energetic man with a passion for confusion. This system uses numbers 000 through 999 to cover general fields of knowledge as follows:

000-099 - Generalities
100-199 - Philosophy and Psychology
200-299 - Religion
300-399 - Social Science
400-499 - Language
500-599 - Natural Science and Mathematics
600-699 - Technology (Applied Sciences)
700-799 - The Arts
800-899 - Literature and Rhetoric
900-999 - Geography and History

The system then narrows down the fields by using more specific numbers, eventually getting into decimals. For example, 500 is Science and Mathematics, 520 is Astronomy, 523 is Specific Celestial Bodies and Phenomena, and 523.44 is Upcoming Planetary Events and Missions. This way the library can add virtually any new material they want, because all fields of knowledge can be classified by ingenious method, most likely under a number such as 420.9112.

This brings me to another point: alphabetical order is still used in the Dewey decimal system. Believe it or not, some books are actually on exactly the same topic, and therefore are assigned the same number. But Dewey didn't stop there. In his never-ending battle with disorganisation, he stated that if there are two or more books with the same number, they must be then further organised alphabetically according to the author's last name, such as "420.9112 T".