First, it helps them preserve rare and fragile objects without denying access to those who wish to study them. The British Library , for example, holds the only medieval manuscript of Beowulf in London. Tokyo's National Diet Library is similarly creating highly detailed digital photographs of 1,236 woodblock prints, scrolls and other materials it considers national treasures so that researchers can scrutinize them without handling the originals. A second benefit is convenience. Once books are converted to digital form, patrons can retrieve them in seconds rather than minutes.
Several people can simultaneously read the same book or view the same picture.
Clerks are spared the chore of reshelving. And libraries could conceivably use the Internet to lend their virtual collections to those who are unable to visit in person. The third advantage of electronic copies is that they occupy millimeters of space on a magnetic disk rather than meters on a shelf. Expanding library buildings is increasingly costly. Not all these benefits can be enjoyed at once.