MK-61 was the best seller of all USSR programmable calculators of 1980-s (B3-34, MK-54, MK-56, MK-61, MK-52).
Calculators are emulated on microcode level so they behave exactly like the original devices, including all non-documented features and inaccurate calculations. For ease of use application features saving and loading emulation states.
This app's emulation engine Java code is based on C++ source of Felix Lazarev's emu145 project.
Emulation was highly optimized for speed and should run in real time on any phone.
Hint 1: touch calculator's indicator to toggle slow/fast mode. Indicator's blinking looks better in slow mode.
Hint 2: you can choose between MK-61 and MK-54 using menu option that becomes visible when calculator is switched off.