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The new hp Prime is wonderful! I am having great fun learning and developing apps for my own particular situation.

I would like to write a program to: make the vars, changes the vars, restore the user vars on my hp Prime. Can anyone help?

The type of variables are real number and the following is an example of the User vars on my Prime:

{Lf, Le, Ql, Pd, Lm, Vl, Dia, BHP, Hr, Prs, Ppm, P1, P2, P3, Wp, Gst, Pst, Ax, Yx, Hx, El, Kva, Vd, Cma, Mns, Ds, Mx, CuM, Usg, Kpa, Mps, Hd, Hrs}

I am using the vars in customized apps such as the following:

copy of Solve app named Electric

Program: Electric

EXPORT Electric()
BEGIN
Electric.E1:='(W/E)=I';
Electric.E2:='(E/R)=I';
Electric.E3:='v((W/R)=I)';
Electric.E4:='v(W*R)=E';
Electric.E5:='(I*Lf*2*10.8/%(3,240))=Cma';
Electric.E6:='(I*Lf*2*10.8/Cma)=Vd';
Electric.E7:='(A*1.25*240/600)=I';
Electric.E8:='(I*E/1000)=Kva';
Electric.E9:='(Usg*Hd/%(80,3960))=BHP';
END;

Electric Solve info:
User vars: Lf, Vd, Cma, Kva

E1: W/E=I
Desc-
vars- W- Watts, E- Volts, I- Amps

E2: E/R=I
Desc-
vars- E- Volts, R- Ohms, I- Amps

E3: SQRT(W/R)=I
Desc-
vars- W- Watts, R- Ohms, I- Amps

E4: SQRT(W*R)=E
Desc-
vars- W- Watts, R- Ohms, E- Volts

E5: (I*Lf*2*10.8/%(3,240))=Cma
Desc- Calc Cma wire size with 3% Voltage drop
vars- I- Wire Amps, Lf- feet length of wire , Cma- wire size

E6: (I*Lf*2*10.8)/Cma =Vd
Desc- Calc Voltage drop for a certain wire size
vars- I- Wire Amps, Lf- feet length of wire , K-10.8, Cma-
wire size, Vd- Voltage drop, 7.2 is 3% of 240
Refer to Notes table for Cma to AWG sizes.

E7: (A*1.25*240/600)=I
Desc- Calc wire Amps
vars- A- Motor Amps, I- Wire Amps

E8: (I*E)/1000=Kva
Desc- Calc transformer size.
vars- I- Amps, E- Volts, Kva- kiloVoltAmps

E9: (Usg*Hd/%(80,3960))=BHP
Desc- Calc Break horse power for a water pump motor.
vars- Usg- US gallons per minute, Hd- Feet head of water
BHP- Break horse power

Notes
American Wire Gauge AWG table:

AWG, Circular Mil area- Cma, Area mm^2

0000 211,592 107
000 167,800 85
00 133,072 67.4
0 105,531 53.5
1 83,690 42.4
2 66,396 33.6
3 52,633 26.7
4 41,740 21.2
5 33,101 16.8
6 26,251 13.3
7 20,818 10.5
8 16,509 8.37
9 13,092 6.63
10 10,383 5.26
11 8,234 4.17
12 6,530 3.31
13 5,178 2.62
14 4,107 2.08

Thank you

Hello,

Yeah the HP Prime is "wonder"ful - as in I wonder how to use it

I have also been messing around with User vars, the solver and the spreadsheet. It is tricky setting up saved equations for use in the Solver, Function or other apps.

In your program, you may have problems defining solver equations like Electric.E1:='(W/E)=I'; as the variables W, E and I are predefined Home variables (with values). So if you then check, E1 in Electric solver, you may see 0=0 or undef=0 if E is zero.

If you used Electric.E1:=Watts/Volts=Amps; then these are "yet" to be defined user variables (Watts, Volts, Amps). Checking E1: should show Watts/Volts=Amps properly. However, when you initially go to the Num view, it will ask if you want to create these three user variables before it performs any numerical solving.

Note that you might also try creating a new "Electric" spreadsheet. In it you can define variables in cells, define equations that refer to these variables/cells and even use some cas commands, like solve() to perhaps perform numerical or symbolic solutions. You still need to be aware of what Home and User variables values (if any) are while using the spreadsheet...

I too, would like to know how to save useful formulas in symbolic form, then use them over and over in Home, Cas, Apps and/or programs. Maybe some experts can guide us.

Best,
Carl

Thanks Carl Food for thought and more questions asked.
I appreciate the comments.
pvrs