What is a Library Catalog?

When researching in a library, especially a research library, its catalog is probably the most important tool you will use, and one with which you should familiarize yourself as quickly as possible. Even if you think you have never used the Library Catalog here, you probably have and just do not realize it, since "Easy Search", the Library's federated search engine, sends all queries to the Library Catalog along with several other online research tools.

A library catalog is a database of records that identify and describe resources owned by the library. Most of these records describe published resources like books. Use the catalog to find both print sources and digitized sources in the Library's collections.

Many research libraries today will dress their catalogs up with fancy interfaces, making the catalogs appear to have far greater functionality than they actually do. You will be a much better user of library catalogs if you understand the purpose and functions of library catalogs, which are in fact very basic:

1. The catalog should be an efficient instrument for ascertaining:
   • Whether the library owns a particular work specified by its title;
   • Whether the library owns a particular work specified by its author;
   • Which works by a particular author are in the library;
   • Which editions of a particular work are in the library.¹
2. The catalog should collocate records for works on a common subject under a single, standardized heading.

Digitization of library catalogs has made it possible to perform keyword searches on the records in the catalog. Aside from this innovation, and a few other conveniences, the library catalogs of today are essentially identical (in function) to library catalogs created a hundred years ago.

If you can't find your book in our Library Catalog, you should next check to see if it's available from an I-Share Library:

After you have explored the books available to you here at the University of Illinois, and also at other I-Share libraries, you will want to expand your search using:

If you find a book in WorldCat that you would like to use for your research, you can request it through:

Subject headings are used to collocate records for works on a common subject under a single, standardized heading.

The subject headings used in the Library Catalog are standardized Library of Congress terms, which may be “subdivided” (made more specific) by geographic area, chronological period, genre, or sub-topic. The language of subject headings is not at all intuitive or natural, so you shouldn’t hesitate to ask a librarian for help in finding the correct subject headings.

A good way to identify subject headings for a topic is to do a keyword search in the Library Catalog using terms you think describe the topic, in order to identify a few relevant books. Look at the full record for those books to see what subject headings were used, then do another search on those headings.

As a rule of thumb, use fairly broad headings, as well as the specific ones that describe your topic, in order to make sure you haven't inadvertently eliminated relevant material that is contained within works of larger scope. Most likely you will find multiple headings to describe your topic, and you should use all of them. You can narrow your search in the online catalog by combining subject headings (as a phrase) with keywords, using the “Advanced Search” option.

It’s true that developing facility with subject headings was more critical in the era of card catalogs. They provided the only subject access to library materials. In online catalogs, you can often identify material on a topic quite easily by searching on keywords. But if you limit yourself to keyword searching, you are likely to miss important material on your topic that uses other terms. For an undergraduate term paper, a keyword search may turn up a few good sources, and that may be sufficient for the purposes of the assignment. But when you’re doing historical research, you won’t want to miss critical material on your topic. A systematic, comprehensive subject search requires searching with subject headings as well as with keywords.

• African American gays.
• Bisexuality.
• Gay liberation movement.
• Gay liberation movement -- California.
• Gay liberation movement -- United States -- History.
• Gay men.
• Gays -- Illinois -- Chicago -- History.
• Gays in popular culture.
• Gays in popular culture -- History -- 20th century.
• Gays in the military -- United States.
• Gays in the military -- United States -- History.
• Gays in the military -- United States -- Interviews.
• Gender-nonconforming people.
• Gender nonconformity.
• Gender identity.
• Gender identity disorders.
• Hermaphroditism.
• Homosexuality.
• Homosexuality -- United States.
• Homosexuality -- United States -- History.
• Homosexuality -- United States -- Interviews.
• Homosexuality -- United States -- Personal narratives.
• Lesbianism.
• Lesbianism -- Archival resources -- Periodicals.
• Lesbians.
• Lesbians -- Biography.
• Lesbians -- United States -- Historiography.
• Lesbians -- United States -- History.
• Lesbians' writings, American.
• Sex change.
• Sex differences (Psychology)
• Sex role.
• Sexual deviation.
• Sexual minorities.
• Transgender military personnel -- United States.
• Transgender people.
• Transgender people -- Biography.
• Transgender people -- Case studies.
• Transgender people -- Civil rights.
• Transgender people -- Civil rights -- United States.
• Transgender people -- Comic books, strips, etc.
• Transgender people -- United States.
• Transgender people -- United States -- Diaries.
• Transgender people -- United States -- History.
• Transgender people -- United States -- History -- 20th century.
• Transgender people -- United States -- Interviews.
• Transsexualism.
• Transsexuals.
• Transsexuals -- Personal narratives.
• Transvestism.
• Transvestism -- History.

For many more subject headings relevant to queer history, see the guide to Queer Subject Headings:

As described in a previous page, you can also use subject headings to find primary sources in the Library Catalog. Use the Library Catalog's advanced search option and include one or more of these Library of Congress Subject Heading form subdivisions in your search:

• correspondence
• sources
• diaries
• personal narratives
• interviews
• speeches
• documents
• archives
• early works to 1800

In order to browse a menu of subject headings in the Library Catalog, you must use an older Catalog interface:

After a new book is assigned subject headings, it is then “classified” according to the Dewey Decimal Classification. UIUC is the largest “Dewey” library in the world. In addition, we use a system called Superintendent of Documents Classification ("SuDocs") for U.S. government publications (based on issuing agency).

In Dewey, the first three numbers indicate the main subject, and additional numbers are added after a decimal point to narrow the subject. Books and journals on historical topics are usually classified in the 900s, although much of social history gets classified in the 300s, and the history of science, technology, and medicine is classified in the 500s and 600s. Religion is classified in the 200s, philosophy in the 100s, literature and literary studies in the 800s, and the fine arts in the 700s.

For more detail on the Dewey Decimal classification consult the Library's Guide to the Dewey Decimal System:

In the 1960s, many libraries adopted the Library of Congress Classification (LCC), but by that time the University of Illinois Library already had more than four million volumes classified in Dewey. Some large academic libraries began using LC classification for new materials and left their older materials in Dewey, splitting their collection in two. University of Illinois debated this approach in 1979, but decided against it, primarily because of the potential inconvenience to our readers, who would have to go back and forth between the systems. Eventually we did adopt LC classification for Music, Law, and materials in Asian languages; older materials in those collections were retrospectively converted to LC classification. Many newer acquisitions, across all disciplines, are now being cataloged in LCC, resulting in a split collection.

For more information on LCC, consult the Library of Congress Classification Outlines:

In order to browse the shelves, you need to know this “classification number”. Once you have identified a few books on your topic by doing a subject search in the online catalog, you can browse the shelf under the same general number(s) to find related works. For example, if you know that the book The Evening Crowd at Kirmser's: A Gay Life in the 1940s, has the call number 306.766 B814e, you could go to the Main Stacks or the History, Philosophy, and Newspaper Library to browse the shelves under the same Dewey number to find related material.

Because so much of the Library collection is now stored in a high density, off-site storage facility, it's no longer possible to browse the collection as completely as it once was. You can, however, do "virtual shelf browsing" using the Library Catalog:

1. International Federation of Library Associations, Statement of Principles: Adopted at the International Conference on Cataloguing Principles, Paris, October 1961, ed. Eva Verona, Definitive ed. (London: International Federation of Library Associations Committee on Cataloguing, 1971), xiii.