Chapter 17. Magnetic Storage

If you've ever seen a punch card, much less had to work with them, you know why computer workers joyously sang the praises of magnetic storage. When all the world and computers were young, the long-term memory of the best computer systems was entrusted to 3.5x8.5-inch sheets of cardboard, punched with rectangular holes, each one storing a single code symbol, a whole card holding about a sentence. A program took a file drawer filled with them. Cardiac arrest required only dropping the drawer, because the order in which the cards were arranged was crucial.

Magnetic storage is faster, more compact, and more permanent. Although magnetic media appear vulnerable (especially if you've had or heard of a disk crash), magnetic records are among the longest-lived of any storage method. In fact, magnetic records store the itinerary of the drifting continents, preserving the details of their shifts in data back at least 250 million years.

In your computer, three different storage systems use magnetism as their working medium, none of them quite as permanent as hot magma but with the potential to outlast you. The most important is your hard disk, without which you simply could not run modern software. The other two magnetic systems are incidental, at least these days. You could live without them, and an increasing number of people do. The teetering twosome includes the floppy disk, as much a vestige of our past as is continental drift (even though most computers still come with a floppy disk drive), and tape, which has declined in importance as people put more faith in the integrity of their hard disk systems.