Differences between Elektronika MK-85 and Casio FX-700P

Even if the Elektronika MK-85 very closely resembles the Casio FX-700P, there exist significant differences between them. Following information is meant as an addendum to the Casio manual for non-Russian MK-85 users, and should help to port programs between both models.

Operators missing in the MK-85 due to lack of printer and external storage support:
```
  SAVE, SAVE A, LOAD, LIST A, GET, PUT, VER
```

Different SET syntax

In the FX-700P the operator SET specifies the number of displayed digits before and after the decimal point. Examples:

  SET E n  - number of integer positions in range 0 to 8,
             value of 0 specifies 8 positions
  SET F n  - number of fractional positions in range 0 to 9
  SET N    - restores the default display format

Examples:

  SET E4
  100/6    - displays 1.667E01
  SET F2
  123/7    - displays 17.57
  SET N
  1/3      - displays 0.3333333333

In the MK-85 the operator SET specifies the total number of displayed positions (in range 1 to 10). Unlike the FX-700P where the number must be specified as a single digit, the MK-85 also accepts an expression. The option SET N works similarly as in the FX-700P, but is not documented. Examples:

  SET 4
  10/3     - displays 3.333
  100/3    - displays 33.33
  SET 10   - releases the limits, recommended method
  SET N    - releases the limits, undocumented method
  10/3     - displays 3.3333333333

Different CSR syntax

The operand of the CSR operator specifies the location where the following data is to be displayed. It can be specified either as a constant or a numerical expression. The fraction part is ignored, the integer part should be in range 0 to 11.

In the FX-700P the CSR operator follows the PRINT statement. Example:

  10 PRINT CSR 2;"ABC"          displays: [ | |A|B|C| | | | | | | ]

In the MK-85 the CSR operator is used before the PRINT statement. Options:

  CSR n    - previous information on the display remains unchanged
  CSR ,    - the right part of the display starting from the current
             position is cleared, then data is displayed at this position
  CSR n ,  - the right part of the display starting from the specified
             position is cleared, then data is displayed at this position
  CSR , n  - the left part of the display up to the specified position
             is cleared, then data is displayed at this position

Examples:

  10 PRINT "012345678901";      displays: [0|1|2|3|4|5|6|7|8|9|0|1]
  20 CSR 2: PRINT "ABC";        displays: [0|1|A|B|C|5|6|7|8|9|0|1]
  30 CSR ,: PRINT "XYZ"         displays: [0|1|A|B|C|X|Y|Z| | | | ]
  30 CSR 7,: PRINT "XYZ"        displays: [0|1|A|B|C|5|6|X|Y|Z| | ]
  30 CSR ,7: PRINT "XYZ"        displays: [ | | | | | | |X|Y|Z|0|1]

The MK-85 doesn't suffer from following bugs present in the FX-700P:
- The VAC command isn't allowed to be used in a multistatement line.
- The EXP function can appear neither in a multistatement line nor in a complex expression. It should be used only with the argument 1 to calculate the mathematical constant e (the base of the natural logarithm).
Example usage of an exponential function on the FX-700P, taken from the manual:
```
  10 E=EXP 1
  20 INPUT A,B
  30 C=(A+E^1.5)/B
  40 PRINT C
  50 GOTO 20
```
The MK-85 doesn't require such workarounds, thus the program can be simpler:
```
  20 INPUT A,B
  30 C=(A+EXP 1.5)/B
  40 PRINT C
  50 GOTO 20
```
In the MK-85 the strings can be compared only with the operators = and ≠, while the FX-700P also supports >, ≥, <, ≤.
In the MK-85 the function MID requires both operands to be specified, while in the FX-700P the second operand may be omitted.
In the MK-85 the function VAL accepts a string variable or a string literal. The parentheses enclosing the argument are optional and can be omitted.
In the FX-700P the function VAL accepts only a string variable in parentheses.
In the MK-85 the index of an array can be negatve, for example A(1) and D(-2) refer to the same memory location, while in the FX-700P it can only take positive or zero values.

New operators specific to the MK-85

CHR n - returns a character of specified code

  CHR 65                 - displays A

ASCI "character" - returns the code of specified character

  ASCI "A"               - displays 65

GETC string, n - extracts a single character from a string or a string variable

  A$ = "ABCDEF"
  GETC (A$,3)           - displays the character "C"

LETC "*******" - defines an user defined character of code 96, asterisks denote bitmap codes from the table below:

  00000 0    01000 8    10000 G    11000 O
  00001 1    01001 9    10001 H    11001 P
  00010 2    01010 A    10010 I    11010 Q
  00011 3    01011 B    10011 J    11011 R
  00100 4    01100 C    10100 K    11100 S
  00101 5    01101 D    10101 L    11101 T
  00110 6    01110 E    10110 M    11110 U
  00111 7    01111 F    10111 N    11111 V

  LETC "LALALAL"        - defines a checkboard pattern
  CHR 96                - displays the defined character

This function cannot be used in a subroutine due to a bug.

DRAW x, y - plots a dot at screen coordinates x (in range 0 to 59) and y (in range 0 to 6), the pixel in the lower-left corner has coordinates 0,0

  10 FOR X=0 TO 59 STEP 2
  20 DRAW X, SIN(X*18)*3+3.5
  30 NEXT X

DRAWC x, y - similar to DRAW except that it clears the pixel

AUTO line_number_interval - automatically supplies line numbers when typing in a new program

TEST - performs a test of the ROM, RAM and display, all programs and data will be erased

WHO - displays information about the author of the firmware (undocumented)

Quantitative differences

	FX-700P	MK-85 or MK-85M
Number of program steps	1568	1221 or 5317
Number of variables	26 up to 222	26 up to 178 or 690
Range of displayed numbers	±110^-99 to ±9.99999999910⁹⁹	±110^-4095 to ±9.99999999910⁴⁰⁹⁴
Operand ranges for the functions
sin x, cos x, tan x	\|x\| < 1440° (8π rad, 1600 gra)	limited only by the representation of numbers
arcsin x, arccos x	\|x\| ≤ 1	\|x\| ≤ 1
arctan x	not specified	\|x\| < 10⁴⁰⁹⁴
log x, ln x	x > 0	0 < x < 10⁴⁰⁹⁴
e^x	x = 1 (note 1)	-9429 ≤ x ≤ +9429
square root	x ≥ 0	0 ≤ x ≤ 10⁴⁰⁹⁴
x^y	x > 0 (note 2)	\|x\| < 10⁴⁰⁹⁴ if x < 0 then y must be an integer

Notes

The PC-4 manual (OEM version of the FX-700P) specifies the supported operand range as:
-227 ≤ x ≤ +230
However, in the FX-700P manual Casio acknowledges some bug in the function EXP and recommends using it only for calculating the mathematical constant e (the base of the natural logarithm).
In the PC-4 manual negative values for the base of the power function are allowed when the exponent is a positive integer.

MK-85 keyboard modes

The key sequence [MODE][.] toggles between the normal and extended keyboard mode.

Normal mode

Pressing a key without any shift enters characters painted on the key caps - upper case Latin letters, digits and other.
The red [S] shift key selects red characters or keywords above the keys.
The blue [F] shift key selects blue keywords below the keys.
The [MODE] shift key selects upper case Cyrillic letters assigned to keys [SPC], [=], [EE], [/], [*], [-], [+], and lower case Latin letters assigned to remaining keys.

Extended mode (indicated by the EXT sign on the display)

Pressing a key without any shift enters lower case Cyrillic letters painted right from the keys.
The red [S] shift key selects special symbols shown on the transparent keyboard overlay.
The blue [F] shift key selects upper case Latin letters.
The [MODE] shift key selects lower case Cyrillic letters assigned to keys [SPC], [=], [EE], [/], [*], [-], [+], and upper case Cyrillic letters assigned to remaining keys.

Other MK-85 features

Turning the calculator on with the key [+] or [M] pressed makes it run several times faster at the cost of increased power consumption.
If an error occurs during program execution, pressing [ANS] displays the program line for editing with the cursor at the position of the error.