Datasheet legend
Ab/c: Fractions calculation
AC: Alternating current
BaseN: Number base calculations
Card: Magnetic card storage
Cmem: Continuous memory
Cond: Conditional execution
Const: Scientific constants
Cplx: Complex number arithmetic
DC: Direct current
Eqlib: Equation library
Exp: Exponential/logarithmic functions
Fin: Financial functions
Grph: Graphing capability
Hyp: Hyperbolic functions
Ind: Indirect addressing
Intg: Numerical integration
Jump: Unconditional jump (GOTO)
Lbl: Program labels
LCD: Liquid Crystal Display
LED: Light-Emitting Diode
Li-ion: Lithium-ion rechargeable battery
Lreg: Linear regression (2-variable statistics)
mA: Milliamperes of current
Mtrx: Matrix support
NiCd: Nickel-Cadmium rechargeable battery
NiMH: Nickel-metal-hydrite rechargeable battery
Prnt: Printer
RTC: Real-time clock
Sdev: Standard deviation (1-variable statistics)
Solv: Equation solver
Subr: Subroutine call capability
Symb: Symbolic computing
Tape: Magnetic tape storage
Trig: Trigonometric functions
Units: Unit conversions
VAC: Volts AC
VDC: Volts DC
Years of production: ? Display type: 7-segment
New price:  SUR 150.00
Display color: Green
    Display technology: Vacuum fluorescent display
Size: 8"×10"×2" Display size: 8+2 digits
Weight: 2 lbs
   
    Entry method: Reverse Polish
Batteries: N/A Advanced functions: trg, exp, log, drg, dms
External power: 220 VAC
Memory functions: N/A
I/O: N/A    
    Programming model: Partially merged keystroke
Precision: 8 digits
Program functions: GOTO, subr, cond, ind
Memories: 14 numbers
Program display: Keycode
Program memory: 98 steps
Program editing: SST, BST, overwrite
Chipset:  K145IK1302, K145IK1303A, KR145IR2 Forensic result:   9.0881454

mk56.jpg (71795 bytes)The Elektronika MK-56 is a desktop version of that Russian workhorse, the Elektronika B3-34 calculator.

Inside a reasonably stylish case is a nice, cleanly designed interior. A small transformer supplies power; small but adequate, judging by its lukewarm temperature after several hours of continuous operation. The layout of the single circuit board is clean, assembly and disassembly is easy. Clearly, it is a machine designed to be assembled by moderately skilled workers, and designed to be field serviceable.

Like other early Russian programmables (it is, after all, functionally identical to the B3-34) the MK-56 is a surprisingly good four-stack RPN calculator. The programming model is clean, stack operation is well designed (and well documented!) much like you would expect from a Hewlett-Packard machine. Yet it is clearly not a copycat calculator; there are enough substantial differences between this and HP models to make that fact clear.

Although the MK-56 provides only 8-digit accuracy, internal algorithms are good, and trigonometric and transcendental functions usually deliver a full 8 digits of precision.

The keyboard is not very good, and not only because of its age. Tactile feedback is terrible (there is no "click"), and the keys often bounce.

RPN and a partially merged programming model made it possible for me to write a nice demonstration of the MK-56's programming model using, what else? My favorite example of course, the Gamma function. This program computes the logarithm of the Gamma function to 7+ digits of precision for both positive and negative arguments using the modified Stirling's formula. Although it doesn't use two advanced features of the MK-56: loops and indirect addressing, it does make use of conditionals and subroutines to accomplish its task without using any memory registers. Note that the calculator must be in radians mode in order for the algorithm to work correctly for negative arguments.

00	50	C/П
01	50	C/П
02	5C	x<0
03	21	21
04	0L	/-/
05	53	ПП
06	21	21
07	0L	/-/
08	14	x-y
09	18	ln
10	11	-
11	14	x-y
12	20	π
13	12	×
14	1C	sin
15	20	π
16	13	÷
17	0L	/-/
18	18	ln
29	11	-
20	52	B/O
21	04	4
22	11	-
23	5C	x<0
24	53	53
25	04	4
26	10	+
27	53	ПП
28	53	53
29	14	x-y
30	01	1
31	11	-
32	0E	B^
33	14	x-y
34	01	1
35	11	-
36	12	×
37	0 	Bx
38	01	1
39	11	-
40	12	×
41	0 	Bx
42	01	1
43	11	-
44	12	×
45	0 	Bx
46	25	Ѻ
47	18	ln
48	11	-
49	14	x-y
50	0Г	Cx
51	10	+
52	52	B/O
53	04	4
54	10	+
55	1E	B^
56	1E	B^
57	1E	B^
58	22	x²
59	22	x²
60	12	X
61	23	1/x
62	01	1
63	00	0
64	05	5
65	13	/
66	14	x-y
67	0E	B^
68	22	x²
69	12	X
70	23	1/x
71	03	3
72	00	0
73	13	/
74	11	-
75	14	x-y
76	23	1/x
77	10	+
78	01	1
79	02	2
80	13	/
81	14	x-y
82	0E	B^
83	18	ln
84	12	×
85	10	+
86	14	x-y
87	11	-
88	14	x-y
89	02	2
90	14	x-y
91	13	/
92	20	π
93	12	*
94	21	√
95	18	ln
96	10	+
97	52	B/O

As a footnote of sorts, recently (July, 2005) I received another MK-56 calculator, with a very different color scheme: