A nice long read from Creatures of Thought on the history of the handheld battery operated calculator, starting in the 60s when the production capability for the integrated circuits barely existed:
Here’s the Cal Tech prototype (“With no good options for an electronic display, output was instead printed onto a paper tape”):
By the end of 1966, Kilby and his team had built a prototype calculator (code named “Cal Tech”): the most compact ever made, at less than three pounds and about four by six by two inches. But it contained four half-inch integrated circuits of about 1,000 transistors each. TI could produce such dense chips only at an experimental scale: each wafer of silicon printed with copies of the Cal Tech circuits yielded only a small number of viable, error-free chips. No one had yet built a semiconductor plant that could realize Haggerty’s dream
via the HP Museum forum, where Steve Simpkin offers more:
The following articles are related. They are from the Articles Section of the Vintage Calculator Web Museum.
The Story of the Race to Develop the Pocket Electronic Calculator - For hundreds of years performing complex calculations was a difficult and tedious chore. Multiplication, division, and taking square roots required paper and pencil and a lot of concentration. Some assistance became available with the invention of the slide rule and logarithm tables, and during the 20th century, the development of mechanical calculators. It was during the 1960s and early 1970s that a great revolution in calculator technology occurred.
The Arrival of the “Calculator-on-a-Chip” - During the late 1960s and early 1970s a major aim of the calculator electronics companies was to integrate all of the functionality of a calculator into one integrated circuit, so producing a “Calculator-on-a Chip”. The development effort eventually led to several companies introducing, around the same time, integrated circuits that provided all of the functionality of a calculator in one integrated circuit - that is they employed a, so-called, “Calculator-on-a-chip”.
The Calculator that spawned the Microprocessor: - The fascinating story of why the development of a calculator led to the development of the first commercial microprocessor, and the unexpected consequences.