HP Calculators Programs - SAC for 12c | TVM for 42s

sac.hp12c

// Constant Amortization System for HP12C (Platinum)
// Author: Henrique Gogó (henriquegogo@gmail.com)
//
// Instructions: enter n, i and PV values and set FV as 0.
// Set register 9 if you want to get an specific payment number.
//
// After program ends, the result saved in registers will be:
// X: current payment value
// FV: remaining amount to pay
// PMT: amortization value (fixed)
// 0: current payment interest
// 1: current payment number
// 2: sum of all payments paid since program started
//
// You can repeat the program while still have payments to be paid.
// If the final payment is reached, the X register will display the final number.
//
// To start/stop programming, just press "f P/R" at begin and end.

// If remaining amount to pay is zero then clear summation
001 RCL FV
002 g x=0
003 f ∑

// If current payment is the last one then finish program
004 RCL 1
005 RCL n
006 g x≤y
007 g GTO 000

// If remaining amount to pay is zero then set initial amount as remaining amount to pay
008 RCL FV
009 g x=0
010 RCL PV
011 STO FV

// Register 0 is the current payment interest
012 RCL i
013 %
014 STO 0

// PMT is the amortization rate 
015 RCL PV
016 RCL n
017 ÷
018 STO PMT

// FV is the remaining amount to pay
019 RCL FV
020 x≷y
021 -
022 STO FV

// Increase the summation of payments
023 RCL PMT
024 RCL 0
025 +
026 ∑+

// If current payment number is less than register 9 then repeat program
027 RCL 9
028 RCL 1
029 1
030 +
031 g x≤y
032 g GTO 001

// Show current payment value and finish program
033 RCL PMT
034 RCL 0
035 +
036 g GTO 000

sac.hp42s

01 LBL "SAC"
02 MVAR "n"
03 MVAR "i"
04 MVAR "PV"
05 MVAR "FV"
06 MVAR "PMTn"
07 MVAR "PMTi"
08 MVAR "PMT"
09 LBL 01
10 RCL "FV"
11 X=0?
12 CLΣ
13 RCL 16
14 RCL "n"
15 X≤Y?
16 GTO 00
17 RCL "FV"
18 X=0?
19 RCL "PV"
20 STO "FV"
21 RCL "i"
22 %
23 STO "PMTi"
24 RCL "PV"
25 RCL "n"
26 ÷
27 STO "PMT"
28 RCL "FV"
29 X<>Y
30 -
31 STO "FV"
32 RCL "PMT"
33 RCL "PMTi"
34 +
35 Σ+
36 RCL "PMTn"
37 RCL 16
38 X<Y?
39 GTO 01
40 RCL "PMT"
41 RCL "PMTi"
42 +
43 LBL 00
44 END

tvm.hp42s

01 LBL "TVM"
02 MVAR "n"
03 MVAR "i"
04 MVAR "PV"
05 MVAR "PMT"
06 MVAR "FV"
07 RCL "i"
08 X=0?
09 1ᴇ-99
10 1
11 X<>Y
12 %
13 ENTER
14 LN1+X
15 RCL× "n"
16 E↑X-1
17 STO+ ST Z
18 RCL× "PMT"
19 X<>Y
20 1/X
21 ×
22 X<>Y
23 RCL× "PV"
24 +
25 RCL+ "FV"
26 END