HP42S  How do I round a number?

03212021, 08:15 PM
Post: #1




HP42S  How do I round a number?
I see the RND command, but I am not understanding how it works because it appears to do nothing.
I want to round an answer in a program to two decimals places. How is this accomplished? TIA HP48GX user learning the HP42s and DM42. 

03212021, 08:27 PM
Post: #2




RE: HP42S  How do I round a number?
From the manual :
Quote:RND: Rounds the number in the Xregister using the current display format. So to round to two decimal places do: FIX 02 RND. 

03212021, 08:30 PM
Post: #3




RE: HP42S  How do I round a number?
Thank you! Coming from the 48G, I can see a lot of the 42 influence on the 48G. Both are great calculators.
I am really starting to love the 42. HP48GX user learning the HP42s and DM42. 

03212021, 08:33 PM
Post: #4




RE: HP42S  How do I round a number?
Type in
Code: 6 

03212021, 08:59 PM
Post: #5




RE: HP42S  How do I round a number?
If you do not want to change the display settings, do (on a 42S)
Code: 2E9 Cheers, Werner 

03212021, 09:17 PM
(This post was last modified: 03212021 09:18 PM by DM48.)
Post: #6




RE: HP42S  How do I round a number?
Thank you everyone.
Werner, Perfect solution. Thank you!! HP48GX user learning the HP42s and DM42. 

03212021, 10:51 PM
Post: #7




RE: HP42S  How do I round a number?
(03212021 08:59 PM)Werner Wrote: If you do not want to change the display settings, do (on a 42S) This is what I typically use  it's 3 bytes shorter: ENTER FP + IP Can't remember where I found that algorithm. It might have been 65 Notes. 

03212021, 10:59 PM
Post: #8




RE: HP42S  How do I round a number?
Note that RND rounds the number in X to what is displayed, in whatever display mode happens to be in effect, and that makes it rather flexible. Used with FIX, you can use it to round to a certain number of digits behind the decimal, so FIX 02 RND can be used to round an amount of money to dollars and cents, while SCI 03 RND will round the number to three significant digits, regardless of its magnitude, which is useful in scientific and engineering applications.


03222021, 04:19 AM
Post: #9




RE: HP42S  How do I round a number?  
03222021, 05:03 AM
(This post was last modified: 03222021 07:47 AM by Werner.)
Post: #10




RE: HP42S  How do I round a number?
In the same vein, SCI 03 rounding: (which, incidentally, also fails for 0.9999.. ;)
Code: 1E8 Cheers, Werner 

03222021, 11:39 AM
Post: #11




RE: HP42S  How do I round a number?
(03222021 04:19 AM)Werner Wrote:(03212021 10:51 PM)Dave Britten Wrote: ENTER Oh right, missed the point about rounding to two decimal places. You can, of course, adjust the magnitude of the number before and after rounding, though that adds additional steps/bytes. 

03222021, 12:19 PM
(This post was last modified: 03222021 12:22 PM by Thomas Okken.)
Post: #12




RE: HP42S  How do I round a number?
Since the point of the exercise is to perform rounding without changing the display mode, maybe using RCLFLAG and STOFLAG is more convenient:
RCLFLAG X<>Y FIX 02 RND X<>Y 36.41 STOFLAG R↓ R↓ (Update: Except that's not possible on the real HP42S...) 

03222021, 03:05 PM
Post: #13




RE: HP42S  How do I round a number?
(03222021 05:03 AM)Werner Wrote: In the same vein, SCI 03 rounding: (which, incidentally, also fails for 0.9999.. ;) A more robust way is with Veltkamp’s splitting, algorithm 3 On various ways to split a floatingpoint number C = 1E30 + 1 // Free42Decimal, SCI 03 (*) Y = C*X Z = XY+Y // Z has 3430 = 4 sig. digits (*) not quite: SCI03 does halfway awayfromzero, Z does banker's rounding. 

03222021, 03:39 PM
(This post was last modified: 03222021 03:39 PM by Werner.)
Post: #14




RE: HP42S  How do I round a number?
Yes, that's where I got it from (well from TJ Dekker) but I thought the shortcut was ok. I should have known better, again :)
so, only 1 instruction more, and this time correct for 0.9999... :) Code: 1E8 Cheers, Werner 

03232021, 07:57 PM
Post: #15




RE: HP42S  How do I round a number?
Now I see why I didn't get a RaNDom number when I pressed RND!
B^) 10B, 10BII, 12C, 14B, 15C, 16C, 17B, 18C, 19BII, 20b, 22, 29C, 35, 38G, 39G, 41CV, 48G, 97 

03252021, 05:39 PM
Post: #16




RE: HP42S  How do I round a number?
(03212021 08:27 PM)Didier Lachieze Wrote: From the manual : yes this is how the HP41 RND function works as well. **vp http://www.series80.org 

03252021, 05:42 PM
Post: #17




RE: HP42S  How do I round a number?
On the 48G, you just do
2 RND and it rounds the number to two decimal places on the first level of the stack (x register for 41/42 users). With the 42, I have to do FIX 02 RND ALL do I don't effect all of the numbers on the stack. HP48GX user learning the HP42s and DM42. 

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