I'm glad you asked :-) I reverse-engineered the Sinclair Scientific calculator, documented its code, and built a simulator: http://files.righto.com/calculator/s

I'm glad you asked :-) I reverse-engineered the Sinclair Scientific calculator, documented its code, and built a simulator: http://files.righto.com/calculator/sinclair_scientific_simulator.html http://files.righto.com/calculator/sinclair_scientific_simul... The short answer is that they used a 4-function calculator chip with just 320 words of ROM and managed to reprogram it into a cheap scientific calculator, a remarkable feat. The tradeoff was that the calculator was very slow and inaccurate.