Thanks, Bill. I see that Google offers Android app versions of the HP11C and HP15C for as little as $3.99.
For those younger math heads, the HP35 which came out in January of 1972, was the first scientific handheld calculator. A few years later (November 1976) I was going through security at the Heathrow airport in London and was questioned thoroughly when they saw my HP21. They’d never seen one like it and needed me to prove to them that it wouldn’t blow up. I was still using it when I sat for my PE exams in 1980. The LED display ate batteries pretty quick, so I borrowed another from a friend so I could make it through the two day exam. I recall that several others sitting for the exam would go occasionally to the back of the room to charge their calculator batteries. When the HP11C came out with an LCD display, batteries would last for years. And it really did fit in your pocket.
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