HP-65
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The HP-65 was the first magnetic card-programmable handheld calculator. Introduced by Hewlett-Packard in 1974, it featured 9 storage registers and room for 100 keystroke instructions. It also included a magnetic card reader/writer whose cards were approximately the size of a chewing gum stick. Like all Hewlett-Packard calculators of the era and most since, the HP-65 used reverse Polish notation (RPN) and a four-level automatic operand stack for efficient use. In Polish mathematical notation, one first supplies the operator and then operands; this is not convenient for use in calculating machines. In reverse Polish notation, one supplies operands first by entering them onto the stack and then one specifies an operator: the operation is performed immediately on the stack contents, the result being returned to the stack. Thus, no equals key is required to tell the machine to complete a calculation; nor are brackets required. There is an enter key to push operands on to the stack. Once learnt, RPN permits easy calculation of very complex expressions, hence its popularity amongst engineers until PCs replaced hand-held calculators.
One curious feature of the HP-65 was that its storage register R9 was corrupted whenever the user (or program) executed trigonometric functions or performed comparison tests (this kind of issue was common in many early calculators, caused by a lack of memory due to cost, power, and/or size considerations). Since the problem was documented in the manual, it is not considered a bug.
Bill Hewlett's design requirement was that the calculator should fit in his shirt pocket. That is one reason for the tapered depth of the calculator. The magnetic program cards fed in at the thick end of the calculator under the LED display. The documentation for the programs in the calculator is very complete, including algorithms for hundreds of applications, including the solutions of differential equations, stock price estimation, statistics, and so forth.
During the 1975 Apollo-Soyuz Test Project, the HP-65 became the first programmable handheld calculator in outer space.
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[edit] External links
- The HP-65 at an unofficial Hewlett-Packard museum (MyCalcDB); includes a photograph of the magnetic card.
- HP's Virtual Museum: HP-65
- HP-65 page at the unofficial Museum of HP Calculators
