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Virtual HP35 

The name 35 derives from the number of keys but in the first series was not reported, needless to characterize a product in the absence of competitors! Its operation is special: it uses the logical principle of Reverse Polish Notation (RPN), designed in the '20s by Jan Lukasiewicz, which allows to describe any formula without the use of parentheses. Before you enter the operands and then operators: (4 + 5) x 6 becomes 4 ENTER 5 + 6 = x and therefore lacks the key =. The RPN eliminate the problems due to parentheses and operator precedence (first division, then the addition etc..). To make a simple example try to find the hypotenuse of a right triangle with legs of 3 and 4 cm, actually easier than with a slide rule: first the calculator must be switched on clicking on the switch located in the upper left, then you can use as normal but when you ahave finished do not forget to turn off the power: the batteries last for a very short time. 
result: 
The Java animation was done by Neil Fraser: from his website
you can download the code and from this link the standalone program.



The current HP 35s: its operation is similar to the model of 1972 


No name for the first calculators: were only "electronic slide rules" 

Nicola Marras 2008 
Credits: Neil Fraser 
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