Topic: Meggitt Algorithms
Interesting web site. I worked for Monroe Calculator in the mid-1970's writing firmware and algorithms for digital calculators. It was just at the time when calculators where starting to use microcontrollers. We worked on our first micro driven scientific calculator (instead of previous discrete TTL logic designs) that used a Rockwell PPS-4/1 4-bit processor. The processor was so new that we had to write our own tools: assembler, linker. At that time we were using the Meggitt algorithms to calculate all scientific functions. The microprocessor could only ADD, it didn't even have a subtraction opocode - you had to do two's complement arithmetic to subtract. The Meggitt algorithms worked superbly. We choose the Meggitt algorithms over the CORDIC equations mainly because, in general, the Meggitt algorithms are converging; meaning that every subsequent digit of precision that was generated was exact. I think this is one of the most beautiful and important characteristic of the Meggitt algorithms, as the results don't oscillate like Newton-Raphson or Cordic. I still have the firmware listing for the calculator (assembly code of course).