Call Numbers

Call numbers are assigned according to the Library of Congress Classification Scheme. The main part of the call number consists of one of two letters, one or more digits, a period (decimal point), a letter, and one or more digits, for instance QA76.A256.

Order

First letters are most important and they are ordered lexicographically. That is, Q precedes QA precedes QC precedes R. Next digits should be read as a natural number. That is, 4 precedes 23. Then there comes a letter (ordering is of course alphabetical). After it there come more digits, this time ordered lexicographically (in other words, they should be treated as a decimal fraction). That is, 23 precedes 4.

How a number is assigned to a journal

The part of the number before the decimal point is assigned according to the subject. For instance, Q is Science (general), QA is Mathematics, QC is Physics, and QA611 is Topology. The letter after the decimal point is the first letter of the name of the journal.

Exceptions

There are many exceptions to the above rules. Here are some of them.

If the subject, like topology, is further subdivided, the first part of the number may contain itself a decimal point, for instance QA611.5.E7.
Do not expect too much logic in assigning the subject to a journal. For instance, Statistics (HA) may be treated as a part of Social Sciences (H), which are not Sciences (Q). Logic (BA) may be treated as a part of Philosophy, Psychology and Religion (B) (perhaps this explains a lot :-) ). While Comptes Rendus (Ser. I: Math.) is classified as Science (Q), Proc. Royal Soc. London (Ser A, Math. and Phys. Sci.) is classified as Mathematics (QA).
Many journals have more than one name. It is impossible to guess what name will be used for classification. For instance, Notices, Proceedings and Transactions of the AMS are under A (QA1.A), while Journal of the AMS is under J (QA1.J). Sometimes the situation is even more complicated, like with the Bulletin of the AMS: the old series is under A (QA1.A), while the new series is under B (QA1.B).
Sometimes classification according to the name is difficult to explain. For instance, Journal of the Mathematical Society of Japan is under S (QA1.S).

Where to find call numbers

You can find call numbers of books and journals at INDYCAT.

Prepared by Michal Misiurewicz

Last updated: 2 March 1998