HP 42s Value Display

[cylurian]

So cool to read these historical background on these calculators.

[Thomas Klemm]

(10-25-2024 07:57 PM)Albert Chan Wrote:  I think TI's ad is honest, showing usefulness of exposed excess precision.

I don't know of an emulator of the SR-51 but we can use the later TI-57 with the following program:

Code:

00   13 lnx
01  -13 INV lnx
02   81 R/S
03   71 RST

If we enter 66666 and repeat running the program, we can see that an error accumulates in register C.
However, only after the 8th execution this is displayed:

0006666600006304 66666
0006666600012904 66666
0006666600019504 66666
0006666600026104 66666
0006666600032704 66666
0006666600039304 66666
0006666600045904 66666
0006666600052504 66666.001

Compare it with the HP-12C:

Code:

   01 {    43 23 } g LN
   02 {    43 22 } g eˣ
   03 { 43 33 00 } GTO 00

f 5
f CLEAR PRGM
66666
R/S

66666.00021

R/S

66666.00021

Here a difference to the original value is displayed after the first iteration but it doesn't change anymore.
This can also be seen with the HP-45 if you set it to FIX 5.

[Steve Simpkin]

There is an article by Dennis Harms ("The New Accuracy: Making 2 to the third = 8") in the Nov 1976 issue of HP Journal magazine that discusses how HP implemented the improved accuracy that William Kahan suggested. The first handheld model that incorporated these improvements was the HP-27. On HP models prior to the HP-27, 2^3 = 8.000000002. On the HP-27 and models after it, 2^3 = 8.000000000.
A PDF of this issue is available here: http://hparchive.com/Journals/HPJ-1976-11.pdf