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9100A desktop calculator, 1968


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Click to go to larger photo of the 9100A desktop calculator.
The 9100A was the world's first programmable scientific desktop calculator.

Really a desktop computer, the 9100A combined Reverse Polish Notation (RPN)—a system for representing mathematical expressions without the use of parentheses—with a special algorithm that could handle trigonometric and logarithmic functions. HP sold the 9100A as a calculator because at the time the perception was that a computer had to be big to be credible. Bill Hewlett said "If we had called it a computer, it would have been rejected by our customers' computer gurus because it didn't look like an IBM. We, therefore, decided to call it a calculator and all such nonsense disappeared."

The 9100A is now recognized throughout the industry as the first desktop computer. In December 2000, Wired Magazine named it the first personal computer.

Additional information:

  • Read an article about the 9100A originally published on HPNOW, an internal HP web site.

  • See an original ad for the 9100A that appeared in Science magazine. (PDF, 1.27MB)

Permission to copy without fee all or part of this publication is hereby granted provided that 1) the copies are not made, used, displayed, or distributed for commercial advantage; 2) the Hewlett-Packard Company copyright notice and the title of the publication and date appear on the copies; and 3) a notice appears stating that the copying is by permission of the Hewlett-Packard Company.

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