Электроника МК-56
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Микрокалькулятор Электроника МК-56
Elektronika Microcalculator MK-56
- Type: Programmable RPN Electronic Calculator
- Size: 9.5 x 8 x 2.25 inches / 24 x 20 x 5.5 cm
- Serial number: 31526
- Date of Manufacture: September 1988
From our friends in the old Soviet Union. This is a desktop RPN scientific calculator featuring a four-level stack, 15 storage registers and 122 program steps. The keys are a little clunky, accuracy is hampered by a lack of guard digits, and it takes a couple of seconds to come back with a result. In other words, it works as well today as the day it was made.
It's always tempting to look at old Soviet tech as a knockoff of American tech. Pure chauvinism, that is. While it's true that there are some similarities to HP calculators (the T-register in the stack will fill in stack levels beneath it, and the last X feature is the same), there are any number of unique features I haven't seen before. Dedicated looping instructions (L0 through L3), special increment and decrement registers, and an odd-but-effective method of displaying program instructions in a right-to-left manner all suggest engineering from near scratch.
Error checking is fundamentally broken, but in a good way. We all know by now that the factorial of 69 is less than 10100 and that 70! is greater than 10100. But key in a quick program to calculate the factorial, and run it. 65 seconds later you'll see an error message on the screen. Ignore that, and divide by 10. Up pops your mantissa, only the exponent is off by one (because you divided by 10, remember?).
The error message is "ЕГГОГ". I first read it in Russian /YEG-gog/ with some puzzlement (and some embarrassment).
What to do with a calculator like this? Well, the factory mark (that little chicken-shaped thing in the box in the upper left of the manufacturer's plate) references a military electronics factory in Kazan, 700 km east of Moscow. So, let's do something military. How about a ballistic missile trajectory? Thought you'd never ask...
BACKGROUND: The horizontal range of a projectile is given by the formula (v2 sin 2a) / g, where v is the muzzle velocity and a is the angle of launch. g is the acceleration due to Earth's gravity, 9.81 m/s2.
USAGE:
- Key in the program below
- Set the angular mode switch to degrees (marked with a Г)
- Enter the doubled angle 2a
- Press the enter (В↑) key
- Enter the velocity (meters/sec)
- Press the run/stop (С/П) key
- Read the horizontal range in meters
- Repeat from step 3 as necessary
| Main Program | |||
|---|---|---|---|
| Addr | Code | Instruction | Comment |
| 00 | 22 | F x2 | square the velocity |
| 01 | 14 | X↔Y | swap with the double angle... |
| 02 | 1C | F sin | ...and take the sine |
| 03 | 12 | × | Multiply by the squared velocity |
| 04 | 09 | 9 | Enter the gravitational constant 9.81 |
| 05 | 0- | . | |
| 06 | 08 | 8 | |
| 07 | 01 | 1 | |
| 08 | 13 | ÷ | ...and divide by it |
| 09 | 50 | С/П | Stop program |
| 10 | 51 | БП | return to beginning for next pass |
(This is an actual example program from the manual for the Электроника МК-61!)
The manufacturer's plate:
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