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Hewlett-Packard, HP-21 Scientific Calculator. This HP-21 was the second generation of handheld calculators and the first of the 20 series introduced in 1975. It was essentially a smaller version of the HP-35 with only 12-digit display and with the known algorithms of Reverse Polish Notion (RPN) and four level stacks. Since the HP-21 had 33% more ROM than the HP-35 it had room for a few extra features, namely: Trig functions in radian mode. Display formatting (scientific or fixed modes). Polar/rectangular conversions. Storage arithmetic (M+, M-, etc.). Power (10^x). |
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