National Semiconductor 750

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In the U.S. the National Semiconductor 600 and then the 650 were one of the cheapest pocket calculator for years, thanks to the cost reduction applied to all aspects. The six-digit LED display without decimal point, the simplified integrated circuit which can be powered directly with a 9V battery, and the low-cost keyboard were all made by National Semiconductor. In addition to these models with two-register RPN logic, which cannot handle decimal fractions, another cheap model, the 750, was introduced in 1975, in which many of its predecessor's bugs were fixed: it was built with a better quality keyboard, used algebraic logic and can handle decimal point. Interestingly, the accuracy of division was only 5 digits.

You can read more about this and competing six-digit models in our special article.