The HP 9820A (AKA the 9800 series model 20) was HP’s third calculator. It made use of many of the same parts used to make the HP 9810. In fact, a number of PC boards were interchangeable between the two. There was, however, a major distinction: The HP 9820A was HP’s first algebraic calculator. It was a fully algebraic calculator with parentheses, precedence and even implied multiplication. (e.g., 2AB meant 2 times A times B.) The calculator displayed the expression as entered on a single line alphanumeric LED display (which showed 16 characters and scrolled as needed) and evaluated it when the EXECUTE key was pressed.
The HP 9820A was originally priced around $5,000 to $6,000 circa 1972, approximately $44K in 2026 USD.
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