Retro Review: Casio fx-3900Pv
Quick Facts
Model: fx-3900Pv
Company: Casio
Years: late 1980s - early 1990s
Type: Finance
Batteries: 1 x CR-2025
Display: 2 lines
Memory Registers: 1 independent with 6 constant registers
Operating System: Algebraic
Programming With Editing!
The fx-3900Pv has a programming module similar to the Casio fx-3600P, its many variations and Radio Shack EC-4004. What separates the fx-3900Pv from the rest is the inclusion of an editing mode.
The display has two lines. The top line has all the mode indicators and program steps. The bottom line is the numeric display.
We are not programming in the blind. Yay!
Run Mode: We execute programs in this mode. [ MODE ] [ . ]
Learn (LRN) Mode: We enter programs from scratch. [ MODE ] [ EXP ]
Edit Mode: We edit programs stored in memory. New entries are automatically inserted. Program steps can be deleted by the [ SHIFT ] [ ↑ ] (CLR) key sequence. [ MODE ] [ 0 ]
There are four program slots. P3 is the shifted program of P1 and P4 the shift of P2.
The programming commands available on the fx-3900Pv are:
ENT: prompts the user for a number. When entering a program, include a valid number after the ENT command. The number entered after ENT is not counted as a program step.
HLT: Halts program execution. In run mode, continue exection with the [ RUN ] key.
RTN: Halts the program execution and returns to the first step. The RTN instruction allows for repeated calculations.
x>0: If the number in the display at the time is positive, the program returns the first step. Otherwise, go to the next step.
x≤M: If the number in the display is less than or greater than the value stored in memory M, go to the first step. Otherwise, go to the next step.
A sample program:
f(x) = x^3 - x^2 ÷ 4 + 1
We will use the first program slot.
P1:
SHIFT: Min (store in Memory M)
x^y
3
-
MR
SHIFT: x^2
÷
4
+
1
=
f(2.2): 2.2 [ P1 ]. Result: 10.438
f(-1.9): 1. 9 [ +/- ] [ P1 ]. Result: -6.7615
Integration ∫dx
In the integration mode ( [ MODE ] [ 1 ]), we can designate one of the four program slots to approximate a definite integral using Simpson's Rule. Memory M is used for x in f(x). The program must start with a Min command and end in equals.
To calculate the integral:
1. Enter integral mode.
2. Pick which program has f(x): P1, P2, P3, or P4.
3. Optional: enter n to specify 2^n divisions, then press [ SHIFT ] [ RUN ].
4. Enter the lower limit, press [ RUN ], enter upper limit, press [ RUN ].
Example: ∫ x^3 - x^2 ÷ 4 + 1 dx for x = 1 to x = 5. Use 16 divisions (n = 4)
[ MODE ] 1 [ P1 ] (see the section above)
4 [ SHIFT ] [ RUN ] (display: 16)
1 [ RUN ] 5 [ RUN ]
Result: 1.496666667 * 10^2
(2^8: 256 divisions returns 1.496666665 * 10^2 , after short while)
The integration updates the memory registers as such:
K1 = a
K2 = b
K3 = 2^n
K4 = f(a)
K5 = f(b)
K6 = integral
Other Features
The other modes of the fx-3900Pv are:
Mode 2: LR. Linear Regression. Fits data to the line y = A x + B.
A: slope
B: intercept
r: correlation
K1 = Σx^2
K2 = Σx
K3 = n
K4 = Σy^2
K5 = Σy
K6 = Σxy
Mode 4: Degrees angle mode
Mode 5: Radians angle mode
Mode 6: Gradians angle mode
Mode 7: Fix point display mode. To round numbers to the fix point internally, execute the RND (round) command.
Mode 8: Scientific notation display mode
Mode 9: Norm mode (floating point)
Registers
[ Kin ]: Stores the number into any register K1 through K6.
[ Kout ]: Recalls the value of K1 and K6.
The M register: < Min >, [ M+ ], < M- > , [ MR ].
Storage arithmetic: [ Kin ] followed by [ + ], [ - ], [ × ], [ ÷ ]
Final Thoughts
The fx-3900Pv improves on the fx-3600P programming module by adding an editing mode.
Missing from is the fractions and fraction-decimal conversions. I would have loved to see other programming commands such as integer part, functional parts, and absolute value. Other than that, the fx-3900Pv is a big improvement of the fx-3600P.
Casio Ledudu page of fx-3900Pv:
https://casio.ledudu.com/pockets.asp?lg=eng&type=417
Eddie
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