Understanding Call Numbers
Unlike most print resources in the library, which are classified with the Library of Congress or Dewey Decimal call number systems, U.S. federal government publications are arranged by the Superintendent of Documents (SuDocs) call number system. The SuDocs system is a provenance arrangement—publications are organized by the issuing agency. So, A call numbers are for the Department of Agriculture, C is Commerce, D is Defense, and so on. There are, of course, exceptions to the straightforward letters: X and Y are used for various Congressional publications.
**See this table on the FDLP.gov website for a guide to the current lettering system for SuDoc numbers, known as class stems. **
SuDocs numbers do not read as a decimal, the way Dewey and LC numbers do. Instead, the numbers before and after the dot are whole numbers. So, while D 19.18 would come before D 19.3 in LC order (because it reads as 19.one eight), it comes after D 19.3 in SuDocs order (because it reads as 19.eighteen). See MSU's SuDocs Basics for more guidance.
A very basic break-down of a SuDocs number:
- I 49.10:999
- First letter indicates issuing department (I=Department of the Interior)
- First whole number before the dot indicates a subordinate office within that department (49=Fish & Wildlife Service)
- First whole number after the dot indicates a category of publication, series, or serial title (10=directories)
- Numbers or letters and numbers after the colon represent individual publications, years, issues or editions (pub date=1999
A Note About SuDoc Numbers:
Each number in a in range until the next number belong to the agency indicated by the first letter, (e.g. all numbers between I 49.1 and I 50.1 belong to the Department of the Interior)