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This 1957 paper describes the first magnetic hard disk for data storage, thus marking a turning point in the history of computing. Developed in San Jose, California, the 305 Random Access Method of Accounting and Control (RAMAC) permitted random access to any of five million bytes of data stored on both sides of 50 two-foot-diameter disks. The magnetic hard disk was adopted throughout the industry. In 1960, the RAMAC 305 was used to score the Winter Olympics in Squaw Valley, California, and to tally votes at both U.S. political conventions.
From a cost standpoint, it is interesting to note that the first IBM hard disk stored about 2,000 bits of data per square inch and had a purchase price of about $10,000 per megabyte. By 1997, the cost of storing a megabyte had plummeted to ten cents. Despite the $10,000-per-megabyte cost, the movable read–write heads of RAMAC finally made it practical to provide interactive computer systems. In 2005, the Magnetic Disk Heritage Center and IEEE honored the IBM RAMAC 305 with an IEEE Milestone Award.
For a related paper, see “The Random-Access Memory Accounting Machine—I. System organization of the IBM 305” by M. L. Lesser and J. W. Haanstra. This paper discusses the design features of this automatic data processing machine that allowed users to eliminate some of the restrictions associated with the traditional batch method for processing business transactions. In particular, the paper elucidates the operational concepts, data transfer routes, and processing controls of the system.
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