HP-12C

The HP-12C is a financial calculator made by Hewlett-Packard (HP) as part of the HP Voyager series.

Functionality

The HP-12C is HP's longest and best-selling product, in continual production since its introduction in 1981. Due to its simple operation for key financial calculations, the calculator long ago became the de facto standard among financial professionals. Its popularity has endured despite the fact that even a relatively simple, but iterative, process such as amortizing the interest over the life of a loan – a calculation which modern spreadsheets can complete almost instantly – can take over a minute with the HP-12C. The 1977 October edition of the HP Journal contains an article by Roy Martin, the inventor of the simple method of operation used in HP financial calculators, which describes, in detail, the mathematics and functionality built by William Kahan (from UC Berkeley) and Roy Martin that is still in use today.

Later HP financial calculators are many times as fast with more functions, but none has been as successful. The HP-12C's programing mode is very intuitive and works like a macro operation on a computer. Basically, the keys one would press in the calculating mode to arrive at a solution are entered in the programing mode along with logical operators (if, and, etc.) if applicable to the solution. After the programing is complete, the macro will run in the computation mode to save the user steps and improve accuracy. There are 99 lines of programmable memory on the HP-12C.