How to create and use user defined keys on the HP Prime. 

Here's the program. You need to initialize 3 variables before running the programs: IC, XC and UCC. Just give them random values. After that, it doesn't matter. 🙂 There might be other variables that needs initializing before first run of the program. Let med know if you learn a better way than mine. Good luck. EXPORT UCC; EXPORT XC; EXPORT XL; EXPORT UR; EXPORT UC; EXPORT UL; EXPORT IL; EXPORT IR; EXPORT IZ; EXPORT SerialRLC() BEGIN LOCAL thechoice = 1; PRINT(); WHILE thechoice == 1 DO CHOOSE(thechoice, "MAIN MENU", "Enter values", "QUIT"); IF thechoice==1 THEN PRINT(); INPUT( {UCC, R, XC, XL}, "Serial RLC filter", {"Voltage:", "Resistance:","Capacitance:","Inductance:"}, { "Input an voltage in volts.", "Input an resistance in Ohm.", "Input an capacitance in Ohm.", "Input an inductance in Ohm."} ); UCC▶UCC; R▶R; XL▶XL; XC▶XC; print("Voltage: " + UCC + " UCC"); print("Resistor: " + R + " Ohm"); print("Capacitance: " + XC + " Ohm"); print("Inductance: " + XL + " Ohm"); Z9 := R+(XL*)-(XC*); Z9▶Z9; PRINT("Impedance: " + Z9 + " Ohm [Vector]"); PRINT("Impedance: " + ABS(Z9) + " Ohm [Scalar]"); PRINT("Angle: " + ARG(Z9) + " degrees"); IF ARG(Z9) < 0 THEN PRINT("Circuit is capacitive."); ELSE PRINT("Circuit is inductive."); END; I := UCC/ABS(Z9); PRINT("Current: " + I + " A"); UR := R * I; PRINT("UR: " + UR + " V"); UC := XC * I; PRINT("UC: " + UC + " V"); UL := XL * I; PRINT("UL: " + UL + " V"); PRINT("Press any key to continue ..."); WAIT(0); END; END; END; EXPORT ParallelRLC() BEGIN LOCAL thechoice = 1; PRINT(); WHILE thechoice == 1 DO CHOOSE(thechoice, "MAIN MENU", "Enter values", "QUIT"); IF thechoice==1 THEN PRINT(); INPUT( {UCC, R, XC, XL}, "Serial RLC filter", {"Voltage:", "Resistance:","Capacitance:","Inductance:"}, { "Input an voltage in volts.", "Input an resistance in Ohm.", "Input an capacitance [XC] in Ohm.", "Input an inductance [XL] in Ohm."} ); UCC▶UCC; R▶R; XL▶XL; XC▶XC; print("Voltage: " + UCC + " UCC"); print("Resistor: " + R + " Ohm"); print("Capacitance: " + XC + " Ohm"); print("Inductance: " + XL + " Ohm"); IF R > 0 THEN IR := UCC/R; ELSE IR := 0; END; PRINT("IR: " + IR + " A"); IF XC > 0 THEN IC := UCC/XC; ELSE IC := 0; END; PRINT("IC: " + IC + " A"); IF XL > 0 THEN IL := UCC/XL; ELSE IL := 0; END; PRINT("IL: " + IL + " A"); IZ := IR + IC* + IL*−; PRINT("Current: " + IZ + " A"); PRINT("Current: " + ABS(IZ) + " A"); Z9 := UCC/IZ; PRINT("Impedance: " + Z9 + " Ohm"); PRINT("Impedance: " + ABS(Z9) + " Ohm"); PRINT("Angle: " + ARG(Z9) + " degrees"); IF ARG(Z9) > 0 THEN PRINT("Circuit is capasitive."); END; IF ARG(Z9) < 0 THEN PRINT("Circuit is inductive."); END; IF ARG(Z9) == 0 THEN PRINT("Circuit is resisitive."); END; PRINT("Press any key to continue ..."); WAIT(0); END; END; END;

@@bernhardarpsrensen many thanks... I had to add "EXPORT IC;" to define IC, but it's all ok. Thanks.