"The first magnetic slurry coating on the first disk drive was poured... from a Dixie cup."
Barry Rudolph, IBM vice president
For most of the twentieth century, the primary medium for data entry, storage, and processing was the punched card. In the 1930s, IBM hired teacher and inventor Reynold B. Johnson (1906-1998) to develop the IBM 805 test-scoring machine to convert pencil marks on forms into punched cards. Twenty years later, Johnson led the team that developed the technology that made the vast majority of punched cards obsolete—the hard disk.
Unlike punched cards and magnetic tape, in which data must be accessed sequentially, hard disk drives provide access to all data almost simultaneously. Some computers in the late 1940s stored data on the outside of magnetic drums, but this left most of the internal space unused. Johnson and his team sought to store data on a stack of spinning disks, vastly increasing the data storage per volume. The main problem they had was preventing the read-write heads from hitting and damaging the disks. Johnson et al. solved this problem by supporting the heads on thin layers of air.
Their 350 Disk Storage Unit, proudly unveiled by IBM in September 1956, held five megabytes of data on fifty 23 1/2-inch (60 cm) diameter platters rotating twenty times a second. By modern standards, the disk drive was a crude device. Fifty years later, IBM introduced the System Storage DS8000 Turbo, which could hold up to 320 terabytes (more than sixty million times more than the IBM 350).
Today, people routinely take pictures with digital cameras, listen to music from a library of thousands of songs on digital audio players, and watch long movies on their computers, all of which depend on sufficient digital storage. Over the past fifty years, storage capacity has doubled every two years or so, a trend that looks set to continue into the future.
