An all-in-one bit exact RPN emulator for the four classic RPN calculators introduced in the 70s. This includes the first pocket calculator (model 35), the first financial calculator (model 80), the first scientific calculator (model 45) and the first programmable calculator (model 65/55). This application employs the same mathematical computation found in the original calculators, providing high precision calculations. Switching between models is simply achieved by touching the calculator screen.