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Dissecting Category Codes

How codes are structured

Although many codes appear to be random strings of characters, there is often an internal logic to them. For instance the Penn State Access code is a person's initials followed by the next unassigned number (e.g. "ejp9" came into the system earlier than "ejp10").

If you can understand the logic of a code system, you can often determine quite a of information from reading a just a code, and you may find memorizing these codes easier knowing what the structure is. You can also use wildcard searches to look for items which have a certain part of a code. Here are just a few examples.

Library of Congress Call Numbers

These items are organized by topic with the call letters representing the general topic and subtopic, the next set of numbers the specific topic, followed by the code for the author then the year of publication.

For instance, the call number for A Handbook of Modern Spoken Breton by Malachy McKenna (1988) is PB2809.M3 1988. This code can be broken down as follows:

If I search the Library card catalog for "Breton language" books, but see references with call numbers starting with anything other than "PB", I can be reasonably sure it is not a book about linguistics or grammar, but some other aspect of the language. In addition, knowing that this book is shelved among the "PB 2809" area shows me that I may find other books on similar topics in this area of the stacks.

See the following links for details on how the Library of Congress call number system works.

• University of Guelph Library of Congress Classification System
• Library of Congress Classification Outline
• About Com Library of Congress

Zip Codes

Zip codes are organized geographically with the first digit representinga region of the country, the second two a smaller subsection or metropolitan area and the last two being post offices in that area. For instance, Pennsylvannia and New York are in the 1 region, while Maryland is the 2 region, New Jersey in the 0 region and Ohio in the 4 region.

The first three codes can also represent a major metropolitan area. For instance, 191xx is Philadelphia, 202xx is Washington, DC and 021xx is Boston.

In fact, zip codes designate such small geographic areas, they are used for detailed demographic research because it is easy to organize material by regions.

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Quick Review

Roll your mouse over the blue box after each question to see the answer.
Note: Answers are already displayed in older browsers.

If the code for a Penn State course is "200405FAUP LING 448 001", then can you identify the - academic year, semester, campus, department, course number and section number?

A: 200405FAUP LING 448 001 is academic year 2004-2005, fall semester, University Park campus, Linguistics, 448, Section 1

If Downtown Baltimore is zip code 21201, then which city is closer to Baltimore - Roland Park (21210) or Westminster (21157)?

A: Roland Park is closer because it shares the first three digits with downtown Baltimore. Westminster only shares the first two.

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This Website is maintained by Elizabeth Pyatt (ejp10@psu.edu) for Teaching and Learning with Technology, a unit of Information Technology Services.

Last Update: July 29, 2005