My apologises if it has already been posted, but after doing a search I couldn’t find anything.
How does the Library of Congress cataloging system work and how does it differ from the Dewey Decimal System?
Like alot of people I was taught the Dewey Decimal System at a young age, so I know how it works pretty well, but I am not to familiar with the LoC system and all the frequently asked questions on the web I can find deal with technically matters for those obviously already familiar with the system instead of a newbie.
Strictly, it’s the Library of Congress Classification system. Cataloguing at the Library of Congress involves a lot more than the LCC.
A few differences between LCC and DDC:
(1) LCC uses both letters and numbers, while DDC only uses numbers.
(2) They have different filing rules. DDC numbers file like decimal fractions (e.g., 009 before 010), while the numbers after the initial letters of an LCC number file like integers: QA9 files before QA10. This makes it a little more difficult to program computers to file LCC numbers.
(3) LCC is a complete shelf-listing system as well as classification system, so (following its rules, together with using the LC shelf-list) you can get a complete call number for an item. DDC only gives you a number fior the subject, and you need to add something to that to get a number for a specific book (and what you add will vary from library to library).
To forestall your next question; LC is used in the bigger libraries for several reasons, one of which is eminently practical; the numbers are shorter. Dewey numbers can be truncated, if you don’t mind trading off specificity and ease of browsing logically, but the fact remains that the numbers for very specific books like those found in academic libraries can be very long. I’ve read that most people can only remember seven numbers at a time. Plus, the more specific a book is (and the longer its Dewey number) the more slender the spine is likely to be.
LC and Dewey put a lot of things in different places and group them in different ways, some of which seem very strange to the casual browser. It’s really all a matter of what you’re used to; many people find LC much easier in a big library because letters with numbers tend to be easier to remember.
Personally, I’d love to redo the art libary I run in something crazy like Colon, just for the fun of it, but I’ll be damned if I’d redo the card catalog.
Just to be really nitpicky, while it’s true that DDC categories don’t include letters, individual books do.
For example, Freeways by Lawrence Halprin is listed at 625.72 H195f.
The H is the first letter of the last name of the author; the f is the first letter of the name of the book. This does make it much easier to find books on shelves in a large category providing one knows the author’s name.
Smaller libraries have taken to a simpler system that just uses the first three letters of the author’s name, as in 625.72 HAL.
Yes, but the parts of the call numbers with letters in them are not part of the DDC number. As I said above, part of the difference between the systems is that LCC gives you the whole call number, while DDC just gives you a number for the subject. In a really small library, you could just use the DDC number, and not worry that several books might have the same number. And I have worked in really large libraries where, for most of the collection, the call number just contains numbers: the DDC number for the subject, and a running number for the books at a DDC number. That’s not very common, however, and in those libraries it probably went back to a practice established at the State Library of New South Wales and the University of Sydney back in the 1890s, when those libraries were a lot smaller.
More specifically, the number of items (digits, or anything) that most people can retain in their short-term memory after brief exposure is about seven plus or minus two. This result is allegedly the basis for AT&T’s original choice of seven-digit telephone numbers for local calls. Both the DDC and LCC cataloging systems are older than this paper however, and so couldn’t have been informed by it.
Which doesn’t mean the catalog designers didn’t know innately that shorter identifiers are easier to remember than longer ones.
In the above example the “H195f” isn’t part of the DDC, it’s the Cutter number (which is a way of identifying authority or authorship).
The conceptual difference between DDC and LoC is that LoC only deals with subject matter that has shown up in the literature, while DDC is an attempt to categorize any subject matter that could possible occur (just keep adding digits). An example: you couldn’t classify “real” fire-breathing dragons in LoC because they don’t exist in real life and thus don’t appear in the literature as such. You can classify fictional fire-breathing dragons as a subject in LoC because they do appear in the literature. In DDC you could classify either because both exist as potential things that could exist.
I love and respect catalogers, but I’m glad I’m a reference librarian.
The letters of the LoC give you a broad idea of the subject, while the numbers give you a more specific feel for the subject inside the broader subject.
Thus you should end up with items about a similar subject near each other.
