Emulator of "Electronika MK 61" and "Electronika MK-54" RPN programmable calculators.

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.

It's an extended version of the original emulator МК 61/54 by Stanislav Borutsky
(https://play.google.com/store/apps/details?id=com.cax.pmk). This version allows to export/import programs from external
files and contains some UI improvements.

Hint 0: you can found the list of all tips in the About dialog
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. 
Hint 3: with the menu "Import" you can import programs from external files, several such programs you can find in https://github.com/xvadim/pmk61-programms
Hit 4: you can open menu by long tap on the "Вкл" label.

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History of changes in previous versions:

MK-61 v1.0 - the first working version
MK-61 v1.1 - fixed UI bugs, speed optimization
MK-61 v1.2 - keep state after pressing Home or Back
MK-61 v1.3 - "About" dialog, enlarged digits, added state saving/loading (up to 50 slots)

MK-61 v1.4
- fix emulation for entering negative power of ten
- 10x speed increase - now works even on old Android devices
- touch indicator to toggle fast/slow mode
- on fast phone use slow mode for blinking
- fixed key press detection
- fixed indicator symbols size
- stable states saving - will be compatible with future versions

MK-61 v1.5
- main screen user interface completely redesigned from the scratch:
* authentic look (as much as possible)
* adaptive behavior that fits any screen from 2 to 10 inch

- launcher icon redesigned

- added slight vibration on button press, more sensible on angle mode change, even more intensive for on/off switch
- screen never goes off even when nothing is touched for a long time

MK-61 v1.6
- added "Settings" page to let user choose vibration and/or disabled screen auto-off
- indicator font size fix for tablets

MK-61 v1.7
- fixed ГРД angle mode switch position (was acting as Degrees mode instead of Grads)
- saved states now can have names. Hint: load and save state to rename it.
- use up to 99 saved states now instead of 50
- added Russian user interface translation
- a number of polishing UI tweaks on the main and settings screens

MK 61/54 v2.0
- added MK-54 emulation
- application name was changed to "MK 61/54" to reflect the fact it supports both devices
- when calculator is switched off, selector button chooses between "MK 61" and "MK-54"
- save states remember which calculator type they were saved with
- old save states use MK 61 device

- added soft "Menu" button on devices that lack hardware menu button
- added support for older Android versions, including Android 1.6
- additional UI polishing for tablets

v2.1:
- "MK 61 ↔ MK-54" button is now menu option (available when calculator is off)
- "About" moved from settings to menu, now with usage hints

- fixed calculator's display font size issue:
 * entering power of ten should not split display into two lines (was an issue on some devices)
 * width should be fully used

- ШГ→/ШГ←/↔ got better labels

- fixed/improved layout on devices with low and medium resolution

v2.2:
- fixed UI scaling issue on normal-mdpi screens
- improved large-mdpi screens

If you still have issues - please let me know device/firmware this happens on.

- added thin border around buttons

v2.3:
- fixed state saving instability on leaving app
- fixed layout resizing glitch
- switching calculator off and state saving/loading became faster

- added user preferences for:
* type of on/off and angle mode switches (checkbox/radio buttons or slider)
* vibration intensity
* buttons outline
* labels text size


