HP 12C Programming Part I: Modulus, GCD, PITI
The last stop (for now) on my 1980s tour is the Hewlett Packard HP 12C calculator, one of the most popular financial calculators of all time. The HP 12C was first manufactured in 1982 and has been seen ever since.
Today, there are two versions of the HP 12C: the original and the Platinum. The original is RPN only and has 99 programming steps of memory. The Platinum edition, first released in 2003, has room for 400 steps and includes Algebraic mode.
In this series, I'll concentrate on the 1982 classic. Albeit, using one manufactured this decade, the processing speed in today's HP 12C's compared to those produced in the 1980s is tremendous.
This is blog is proerpty of Edward Shore, 2016.
The last stop (for now) on my 1980s tour is the Hewlett Packard HP 12C calculator, one of the most popular financial calculators of all time. The HP 12C was first manufactured in 1982 and has been seen ever since.
Today, there are two versions of the HP 12C: the original and the Platinum. The original is RPN only and has 99 programming steps of memory. The Platinum edition, first released in 2003, has room for 400 steps and includes Algebraic mode.
In this series, I'll concentrate on the 1982 classic. Albeit, using one manufactured this decade, the processing speed in today's HP 12C's compared to those produced in the 1980s is tremendous.
HP 12C Modulus
This program takes the modulus of two numbers:
Y MOD X = X * FRAC(Y/X)
In this program, X > 0 and Y > 0.
STEP

CODE

KEY

01

10

÷

02

43, 36

LST x

03

34

X<>Y

04

43, 24

FRAC

05

20

*

06

43, 33, 00

GTO 00

Input: Y [ENTER] X
[R/S],
Result: Y MOD X
Test 1: 124 MOD
77 = 47
Test 2: 3862 MOD 108 = 82
HP 12C Greatest
Common Divisor (GCD)
This program calculates the greatest common divisor of
two integers. You can enter the two
integers in either order.
Program:
STEP

CODE

KEY

COMMENT

01

43, 34

X≤Y

Determine which
integer is greater

02

34

X<>Y


03

44, 1

STO 1

R1 = max(X,Y)

04

34

X<>Y


05

44, 0

STO 0

R0 = min(X,Y)

06

45, 1

RCL 1

Begin Euclidian
division routine

07

45, 1

RCL 1

Recall R1 twice

08

45, 0

RCL 0


09

10

÷


10

43, 25

INTG


11

45, 0

RCL 0


12

20

*


13

30




14

43, 35

X=0


15

43, 33, 21

GTO 21


16

34

X<>Y


17

44, 1

STO 1


18

34

X<>Y


19

44, 0

STO 0


20

43, 33, 06

GTO 06


21

45, 0

RCL 0


22

43, 33, 00

GTO 00

Input: integer
[ENTER] integer [R/S]
Result: GCD
Test 1:
GCD(142,25)
Input: 142 [ENTER]
25 [R/S]
Result: 1
Test 2: GCD(2555,
1365). Result: 35
HP 12 PITI
(Principal, Interest, Taxes, Insurance)
Here is a simple program that calculates the payment
(principal and interest) while taking property taxes and insurance in
consideration. Property taxes and
insurance are assumed to be combined as an annual amount. Payments are assumed to be on a monthly
basis.
Program:
STEP

CODE

KEY

COMMENT

01

1

1


02

2

2


03

10

÷

(tax + ins)/12

04

44, 0

STO 0


05

14

PMT


06

14

PMT

Need to press
PMT twice. Second press calculates
payment.

07

45, 0

RCL 0


08

16

CHS


09

40

+

PITI is assumed
to be an outflow

10

43, 33, 00

GTO 00

Ends the program

Input:
Number of Years [ g ] [ n ] (12*)
Annual Interest Rate [ g ] [ i ] (12÷)
Loan Amount [PV]
Annual Property Insurance and Taxes [R/S]
Result: PITI
Test: Calculate
PITI for a 30year loan of $205,000. The
rate on the loan is 4.1%. Annual
insurance and property taxes are estimated to be $1,102.50.
Input: 30 [ g ] [
n ] (12*), 4.1 [ g ] [ i ] (12÷), 205000 [PV], 1102.50 [R/S]
Result:
1,082.43 (PITI = $1,082.43)
This is blog is proerpty of Edward Shore, 2016.