![]() The HP-12C and the other members of the HP-10C line all used the same CPU, referred to as Voyager, with different code assigned to the different buttons on each model. When you push a button the calculator is actually loading a tiny program into the CPU. Unlike most pocket calculators which have a relatively primitive fixed-function calculator IC there is actually a CPU inside of an HP-12C. Because there’s a stack there’s a fairly sophisticated memory function basically built in. At this point the stack looks like this:Īs a result, when the divide button is pressed 13 and 8 are popped off of the stack and 8 is divided by 13 giving us 0.62. Then 7 is pushed onto the stack, 6 is pushed onto the stack and they’re added together to make 13, which is pushed back onto the stack. So 3 is pushed into the stack and then 5 is pushed into the stack and then + pops them off the stack and then pushes the answer 8 back onto the stack. The tricky bit to imagine in that example above is that each time you enter numbers, the stack is being pushed down. Basically each new number you put in is pushing down a new entry on the stack and each operation is popping off numbers from the stack in a last-in, first out order. As computer science buffs are aware, RPN works on a stack. The beauty of this is that in RPN the order of operations is explicit. RPN: 9 strokes, and no need to write anything down. Touch the divide key and the calculator gives the answer, 0.62.Īlgebraic: 13 strokes, not counting the effort to write down or memorize the first answer while you calculated the second answer. Note that the answer to the second sum is displayed. Now enter the 8 from the first answer and then divide it by entering the second answer to get x=0.62. Write down the answer or store it in memory. If you think about it, you have to modify the way you learned math in order to use an algebraic mode calculator.Īlgebraic method: Add 3+5=8. It’s best if I let this page at HP’s site about RPN explain the difference:īelieve it or not, the process of using RPN is similar to the way you learned math. Why would you want a calculator that works like this? You enter the numbers first and then the operation. Then you press 4 then you hit the + button and your two numbers are added together and 6 shows up on the screen. Instead, you press 2 and then press Enter. In order to add two numbers you do not type 2 + 4 and press =. Unlike most calculators the HP-12C uses Reverse Polish Notation (RPN). The HP-12C apparently has endured because finance professionals loved their portability and reliability of the HP12-C and required newcomers to learn how to use them. The HP-12C is a member of a line of calculators that HP created for different professions in the early 1980s including the HP-10C, HP-11C, and HP-15C scientific calculators and the HP-16C programmer’s calculator. ![]() The HP-12C is one of the last remnants of that era. But, there was a time when a calculator was a prized possession, probably the most advanced piece of technology a person owned. Today the vast majority of pocket calculators and small desktop calculators you see are extremely cheap commodity crap. I don’t actually have much use for a financial calculator but I bought this HP-12C for two reasons: First, because a Reverse Polish Notation calculator seemed like a great nerd novelty item and second because it’s a classic of early 1980s technology. You can buy one new at Amazon, or from Staples, or OfficeDepot, or Walmart and the price you will pay is not what I would call cheap. Despite the fact that it was first released in 1981 (the same year as the IBM PC) it’s still being sold today. HP even posted a celebratory video on YouTube entitled HP 12c Calculator - Then & Now. When it turned 30 in 2011, it was covered in the Wall Street Journal and on major blogs like Technorati. To the extent that it’s possible for a pocket calculator to be legendary, that’s what the HP-12C is. It came in this beautiful case and just required some new batteries to start working. This is my HP-12C financial calculator, which I bought from Shopgoodwill last year.
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