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Library of Congress Classification

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Books showing call numbers

Library of Congress call numbers provide a way to organize a collection of volumes, keeping similar items together and allowing us to find a specific book among thousands of others. In general, a book's call number acts as its address on the shelf. The call numbers are read left to right, volume by volume on each shelf, top to bottom on each section of shelving.

All call numbers have at least three lines. Some have as many as five. There are specific rules of arrangement:

1. Similar call numbers are grouped together, and they run progressively, in ascending alphabetical and numerical order.  An AC call number would be shelved to the left of an AD call number; Q would come before QA; QA 75.6 would come before QA 76, and so on.  Sample call numbers
2.  The call numbers are read from the first line, alphabetically by letter(s), then by the second line's number, and then by the third line's letter and decimal number.  The number on the third line is a decimal number, whether or not the decimal point is present.  Although the call number in InfoLinks is displayed straight across, for example: BF575.F66 D83 1983, the call numbers will be displayed vertically on the spines of the volumes. BF

3. The fourth line of the call number may be a mixed (letter and number) term.  If so, it is read in the same way as the third line-- by letter and by decimal number.

4. The fourth line (or sometimes the fifth line) may be a date, usually the year of publication.  If all the elements of the call number are identical, the volumes are shelved in order of publication year. This is useful for distinguishing editions of a work or volumes of a journal.

NPG 7/98