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Library of Congress Classes & Shelving

Arrangement of Books

Now for the final step - finding the book on the shelf!  As you might have guessed (or already knew), the call numbers run left-to-right on the shelves from A (then A1, A2, etc.), to AB (AB1, AB2...) to AC, and so on to AZ, and then start over with B, BA, BB ... BZ and so on.  But what about the rest of it?  Let's look at a picture of some actual books living on the LNDL shelves:


Library books in LC call number  order


These books all share a major classification (B), a subclass (F), a class number (723), and they even share the first Cutter number (.P25), which is a subject Cutter.  Where they differ is in the second Cutter number - the author Cutter.  Take a look at the two middle books.  If these books are supposed to be ordered from left to right, why does S63 come before S7?

The reason is that both subject and author Cutter numbers, unlike the class numbers that follow the initial letters, are to be read as decimals.  In a class number, BF723 will come before BF7222, because 723 is smaller than 7222.  But in a Cutter number, S6 followed by any number will always come before S7 (followed by any number).

Cutter number sequencing is really the only tricky thing about finding a book on the shelf!  Everyone understands that A comes before B and that numbers run from low to high - but no one tells you that the numbers after the first number are decimals!  No one until now, that is.  You're welcome.