HP 42S Programming Part I:
Matrix Column Sum, GCD, Error Function
Continuing with calculators from the 1980s, this series will present one of the most beloved scientific calculators and one of the most sought after: the Hewlett Packard HP 42S from the late 1980s. If you want one, you might want to save up because HP 42S calculators are valuable, and often cost over $100.
It is one of my most favorite calculators of all time.
Free42
However, you can use an emulator for the HP 42S for free, check out the Free42 by Thomas Oakken. It is a rewrite of the HP 42S code and the emulator is available on many platforms including Widows, Mac, iOS, and Android. Link: http://thomasokken.com/free42/
Oakken accepts donations.
Link to Part II: Dew Point, Ellipse Area and Eccentricity, Easy Transverse
Part III hopefully to come next week.
As usual, anything that comes after the double-backslash is a comment only.
HP 42S: Column Sums of a Matrix
This could potentially had been a medium to long sized
programs involving loops, but thanks to the powerful function RSUM (found in
CATALOG-FUNC or executed by XEQ RSUM) this program will be quite short. RSUM is the row sum function, or the sum of
each row of a matrix.
Just put a matrix on the stack and run CSUM. When the program is finished, press [shift] [
9 ] (MATRIX), {EDIT} to see the sums.
00 {12-Byte Prgm}
01 LBL “CSUM”
02 TRANS \\ transpose
03 RSUM
04 END
Test: MAT1 = [ [4, 3,
1], [5, 8, 2], [7, 6, 3]]
Result: [16, 17, 6]
HP 42S: GCD (Greatest
Common Divisor) by Euclid Division
Enter the two integers on the Y stack and X stack. Order doesn’t matter.
00 {42-Byte Prgm}
01 LBL “GCD”
02 X<Y?
03 X<>Y
04 STO 01 \\ store
maximum in R01
05 X<>Y
06 STO 00 \\ store
minimum in R00
07 LBL 00 \\ main loop
08 RCL 01
09 ENTER
10 RCL÷ 00
11 IP
12 RCL* 00
13 –
14 X=0? \\ is max –
IP(min/max)*min = 0?
15 GTO 01
16 X<>Y
17 STO 01
18 X<>Y
19 STO 00
20 GTO 00
21 LBL 01 \\ display GCD
22 RCL 00
23 “GCD:”
24 ARCL ST X
25 AVIEW
26 END
Test: Find the GCD
of 485 and 175.
485 [ENTER] 175 [XEQ] {GCD}
Result: 5
Alternatively:
175 [ENTER] 485 [XEQ] {GCD}
Result: 5
HP 42S: Error (erf)
Function
ERF(X) = ∫ 2/√π * (e^(-T^2)) dT, from T = 0 to T = x
Integrand:
00 {22-Byte Prgm}
01 LBL “ERF”
02 MVAR “T”
03 RCL “T”
04 X^2
05 +/-
06 E^X
07 2
08 *
09 PI
10 SQRT
11 ÷
12 END
Instructions:
Press [(shift)] [ 8 ] (∫ f(x) )
Choose ERF at the “Select ∫f(x) Program”
Select T at Set Vars; Select ∫var
Store 0 in LLIM, X in ULIM, a suitable accuracy factor
(10^-n) in ACC
Press the ∫ soft key.
Test: erf(1.2) with ACC of 1E-6 (LLIM = 0, ULIM = 1.2)
Result: 0.9103