Enter the computer.

Suddenly librarians could “place” documents in more than one virtual location, bearing no connection to their physical location on the shelf. The computer could find any document easily and efficiently, even if it had multiple subjects, and it could “place” it together with related books in each of those categories. Not only that, but the computer could also create a bibliography of any given subject, with location pointers for each document. Although it seemed like a new world, the traditional methods of shelving books did not change, since many users wanted the opportunity to browse the shelves. They wanted to see all the books on a single subject in one location (even though they were certainly fooling themselves, since many of these books were obviously in other locations!).