Another reason to respect the great scientists of ages past was that they accomplished everything without using calculators. Ptolemy and Galileo calculated planetary motion; Netwon invented the field of calculus; and Einstein came up with the theory of relativity without even punching in equations into a mechanical device. They used thick booklets with pre-calculated functions, slide rules, and various semi-mechanical devices. Even at the start of the electronic age, the first calculators used vacuum tubes and were incredibly bulky. It took the Hewlett Packard company many years of development to come up with the first more or less portable scientific calculator.

On this day, February 1st, in 1972, the HP-35 went on the market in the U.S. It was priced at $395 dollars (around $2,000 in today’s terms).

The HP calculator was not the first one on the market – a Japanese EL-8 model appeared in Japan a year earlier – but it was the first to integrate advance functions, such as sines and cosines, as well as the first to perform the first logarithmic functions. It was essentially the first electronic slide rule, and a precursor to modern day graphing calculators.