As libraries around the world transition from hardbound books to digital files, at California State University, Northridge, a massive infrastructure keeps things running.

Behind the scenes, 13,000 book bins are stacked 12 meters high in an automated system that can retrieve a book in seconds.

With more than one million books and a quarter-million periodical volumes housed at this suburban Los Angeles campus, catalogs are already digitized and students download readings for class. But the library is also home to thousands of rare books and documents.

"I would say that probably 90 percent of the journals that we subscribe to now come in electronic format," says Mark Stover, dean of the library, explaining that print treasures - such as an 18th-century travelogue — are here to stay. "With books and monographs on the other hand, it's a little bit different story."

Although their facility is changing, Northridge librarians say, their printed books should be around for a long time. In fact, most of the library's book holdings and new acquisitions are in paper form.

Some students like it that way.

"I like the computer as well, but I prefer book and paper," says biology major Lisa Ochoa.

The library's collection includes printed archive material, such as handwritten letters and old newspaper stories, but a major effort is under way to digitize the holdings to preserve them and widen their availability.

According to digital librarian Steve Kutay, encoding electronic files with descriptive "metadata" ensures they will remain accessible.

"They can be backed up and they can be stored off-site," he says. "They can be very well protected, but are not necessarily meaningful to us if we don't know - 10, 20 years from now - what is contained in those files."

Helen Heinrich, chief of technical services, oversees cataloging of new books and periodicals, and removing books that have already been converted to digital format. Many universities, she says, are cooperating to ensure hard copies remain in storage in case of an emergency.

"We are all becoming so dependent on the Internet," she says. "But what if there is a cyber-attack and it all goes down one day? there will be a copy of record."

Dean Stover says that although going digital gives libraries extra room and the opportunity to redesign their physical layout, it's not a complete conversion. For books, the process is gradual, and he says many digital files remain unavailable because the authors or their heirs retain copyrights and won't release them for electronic distribution.

"We are going to weed our collections. We are going to reshape them and use the space to repurpose into more learning places for our students," says Stover. "But I think that print books, especially because of copyright issues, are going to maintain their place for many years to come."

Fortunately, he adds, most students are comfortable with either format.