Encyclopedia of Computer Science and Technology

36 backup and archive systemsthe economic value of data has increased. Potential threatsto data include bugs in the operating system or softwareapplications, malicious acts such as the introduction ofcomputer viruses, theft, hardware failure (such as in harddisk drives), power outages, fire, and natural disasters suchas earthquakes and floods.A variety of general principles must be considered indevising an overall strategy for creating and maintainingbackups:Reliability: Is there assurance that the data is stored accuratelyon the backup medium, and will automatic backupsrun reliably as scheduled? Can the data be accuratelyretrieved and restored if necessary?Physical storage: Is the backed-up data stored securely andorganized in a way to make it easy to retrieve particulardisks or tapes? Is the data stored at the site where it is tobe used, or off-site (guarding against fire or other disasterstriking the workplace).If it had been built, Charles Babbage’s Analytical Engine, althoughmechanical rather than electrical, would have had most of theessential features of modern computers. These included input,(via punched cards), a processor, a memory (store), and a printer.A reproduction of part of the early Difference Engine is shownhere. (Photo Researchers, Inc.)to manipulate memory addresses did the design fall short ofa modern computer.Further Reading“The Analytical Engine: the First Computer.” Available online. URL:http://www.fourmilab.ch/babbage/. Accessed April 20, 2007.Babbage, Henry Prevost, ed. Babbage’s Calculating Engines: A Collectionof Papers. With a new introduction by Allan G. Bromley.Los Angeles: Tomash, 1982.Campbell-Kelly, M., ed. The Works of Charles Babbage. 11 vols.London: Picerking and Chatto, 1989.“Who Was Charles Babbage?” Charles Babbage Institute. Availableonline. URL: http://www.cbi.umn.edu/exhibits/cb.html.Accessed April 20, 2007.Swade, Doron D. “Redeeming Charles Babbage’s Mechanical Computer.”Scientific American, February 1993.backup and archive systemsThe need to create backup copies of data has become increasinglyimportant as dependence on computers has grown andThe daughter of poet Lord Byron, Lady Ada Lovelace (1815–52)acquired mathematical training usually denied to her gender.When she met Charles Babbage and learned about his computerdesign, she translated his work and wrote the world’s firstcomputer programs. (Photo Researchers, Inc. / SciencePhoto Library)