Calkins Calculators

I saw a picture the other day and it reminded me of Dad and the assortment of equipment he used to calculate numbers. Going back as far as I can remember, Dad used his trusty slide rule. Never needed batteries or power of any kind. Never crashed unless you dropped it. And it did not need upgrading for many, many years. This is a picture of the actual slide rule Dad used at Wayne State while he was there. I am pretty sure he used this on his job, probably up to some time in the 60's.

Some time in the early 60's, I know he used a Frieden mechanical calculator. Does anyone else remember those days in late March and early April when Dad would bring this calculator home from work for the weekend when he worked on taxes? I can still hear the whirring motor and the clunkity, clunk, clunk of the thing as it added two numbers together. He let me play with it a few times, but not until he was completely done with the taxes. The calculator had 8 digits to the left of the decimal point. Wow. Now I know why Dad had to bring it home to do the taxes - we were millionaires!

Then I guess PennSalt decided to go high-tech and I remember Dad got another Frieden calculator with a CRT screen. For its time, this was truly an advanced, state-of-the-art, high-tech calculator. The only equipment more advance than this was a mini-computer. Dad would also bring this one home at tax time, but I remember it was basically hands-off for me. I have no idea what this cost to buy back then, but I am guessing it was about the price of a new car. I remember that just before Dad retired, something had gone wrong with this calculator but since it was so old, Dad could not find a place to get it fixed. He brought it home and asked me if I could maybe fix it. I remember taking it apart and seeing all the circuit boards inside. I tried all the tricks I could think of to make it work again, but I couldn't. By this time however, technology had marched on and Dad had a new digital computer.

Some time before the Frieden had problems, Dad got a Texas Instruments SR-10 hand-held calculator. This thing was small, lightweight, and if you had big enough pocket, it could be stowed there. Slung on one's waist with the supplied carrying case, all an engineer or mathematician needed was a pocket protector to have the ultimate in Nerd Kits.

Besides addition, subtraction, multiplication and division, it had square root, square, and inverse functions. Another amazing thing about this calculator is it had scientific notation, where extremely large numbers could be entered and calculated. Dad paid $140 for his calculator. I had just started college after Dad got his calculator, and after using his, I just had to have one! This is really a picture of my calculator I bought for $120 about a year after Dad got his. Well, come to think of it, I am sure Dad paid for it. I actually did use his slide rule for a short while in college, but quickly switched to this and used it for the rest of my days at school.

Oh, and I almost forgot Dad's last calculator. I think Dad was pretty impressed with a Hewlett Packard calculator I got about the time I graduated from college. So, he bought the one shown here, an HP-11C. Years later, I was pretty impressed with the sleek one he got, so I got one identical to it (which I still use in my office). In typical Dad fashion, notice he used a label maker to put his initials on it. We still use this calculator today for various family calculations. In fact, it is about the only calculator we use. The odd thing about HP calculators is they use reverse Polish notation (RPN). Only a nerdy engineer could appreciate RPN and most others would not know how to use it. But most people I explain it to, eventually come around to liking it better than the way a conventional calculator works. (Converting the world, one calculator user at a time, to nerd-dom!)