Most people use the library for the following:
1. To find a book they already know they want;
2. To research a question they’ve already formulated;
3. To learn more about a topic they’re interested in.
To find a book you already know you want, use the library catalog.
To research a question you’ve already formulated, use the appropriate catalog or index. [hint: in the sciences, start with the appropriate subject index; in the humanities, start with the library catalog.]