If you're moving to Concord, New Hampshire to work on copper lugs in a factory or a workshop and you're not into reading as a hobby, you might think you have no reason to ever step foot into the Concord Public Library. After all, everything's on the internet these days, right? Wrong. There are still many subjects that are only imperfectly covered on the internet, and those that are, how can you trust that the information is accurate? Chances are you'll find yourself in the library at some point, and when that happens you'll want to be familiar with the Dewey Decimal System.

The last time you heard of the Dewey Decimal System was probably in elementary school. Since then the books you've seen, if they're in any order at all, are listed alphabetically. However alphabetization by author would make it extremely difficult to round up all the books on industrial insulation. One author might be called Aardvark and the next Zimley. Therefore there needed to be a better ordering system to make reference books more accessible.

In 1876, Melvil Dewey invented that system: The Dewey Decimal System. In his system, reference books are divided up into ten main categories identified by a number. Since knowledge has expanded quite a bit since the 1800s, the system has undergone more than 20 revisions. The current ten base categories are: Computer science, information & general works (000), Philosophy and psychology (100), Religion (200), Social sciences (300), Language (400), Science including mathematics and time and frequency standards (500), Technology (600), Arts and recreation (700), Literature (800), and History, geography, and biography (900).

Within each category subjects are further refined by additional numbers to reflect the country the book is concerned with and the sub-categories (such as recreation - gardening - hand garden tools) so that by finding the correctly numbered section you can look at all the books on the subject. Though the Dewey Decimal System has a place for fiction (listed under 813) most libraries shelve it alphabetically by genre (e.g. romance, mystery).

To find a book on lead aprons under the Dewey Decimal System, you don't have to know the exact number designation for radiation protection. You can use the library's online catalog to search for it by subject. Then you need only write down the number they give you and find the corresponding section on the shelves. It will be identified by signage.