Call numbers are used to arrange the books on the library's shelves so every book has a specific location. If you know how to read them you'll be able to find any book the library has.
Here's a breakdown of the call number RA643 .W37 2009
|RA||Read the beginning letters in alphabetical order: (A, B, C...R, RA , RB...Z)|
|643||Read the first number (including decimal points) in numerical order: (1, 2...100...500...640, 642.8, 643 , 643.5, 644...1000)|
|.W37||The next piece is a combination of letters and numbers. Read the letter alphabetically and the number as a decimal (.W1, .W2, .W21, .W22, .W229, .W3, .W37 , .W4 ... .W63, .W631, .W64, .W7)|
|2009||This is the year the book was published - helpful if there are multiple editions of the book.|
Here's how call numbers look in the library catalog:
And, here's how they look on the shelf:
Browsing is a great way to find books. The books in the library are arranged so that books on similar topics are nearby each other. If you get the call number for one book that covers your topic, there’s a good chance you’ll find more on the shelf nearby it.
Modified from: http://cooklibrary.towson.edu/help-guides/understanding-call-numbers