HP-35

Hewitt-Packard stunned the engineering community when they made a highly functional scientific calculator fit in a pocket.

John Bottoms was the first in my circle of friends to own one. I bought his when he upgraded to the improved 45.

The 35 had four registers organized as a stack. A keystroke would replace the first two registers with a single result. The fourth register would be duplicated into the third when the stack was thus shifted.

A technique was to fill the stack with some interesting number and then repeat a calculation incessantly.

This would be entered into the calculator in post-fix order, operands first then the operators. The register duplication creates the rest of the needed 2's.

The post-fix notation, called reverse-polish notation or RPN, was popular among those who wanted to watch a calculation.

Eventually RPN was displaced by in-fix notation with parenthesis which was preferred by those transcribing written formulas and only interested in the answer.

I was programming small computers at the time and often needed to calculate the number of bits required to hold a particular quantity, the log base 2 of the quantity.

I found that I could understand logarithms more completely by playing with them on the calculator. I was suppose to know this stuff already but the tactile manipulation with the calculator drove it into my intuition.

I did a lot of bit-capacity calculations for the Super Duper which squeezed six-letter ham callsigns into two bytes.

See other Handheld Calculators