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[34S & 31S] Unique display mode: significant figures
02-07-2015, 10:13 PM
Post: #4
RE: [34S & 31S] Unique display mode: significant figures
(02-07-2015 09:01 PM)Bit Wrote:  The WP 34S and 31S have for a long time had a compile time option to add the rarely seen 'significant figures' display mode, implemented by Nigel. Very few calculators offer this feature, one example is the Commodore S61 from 1976. Nigel and I have recently been working on some improvements, have fixed a few minor issues and introduced an intuitive user interface. Two new modes are available: SIG and its zero-padded variant, SIG0. Both modes accept arguments from 0 to 7, allowing up to 8 of the most significant digits to be displayed.

In the 31S, these display modes can simply be selected from the DISP menu. In the 34S, [h] [FIX] opens a catalog where you can navigate using the arrow keys or simply by pressing [B] again to select the new modes (there's no need to press ENTER before entering the mode argument) as illustrated below.

[Image: attachment.php?aid=1585]

Significant figures modes format numbers to a number of significant digits equal to one more than the mode argument. Unlike SCI or ENG mode, exponent notation is not used unless the number is outside the range 10-4 to 109. Trailing zeros are removed in SIG mode and displayed in SIG0 mode. Entering pi and successively multiplying or dividing it by 10 will display the following in SIG 4 mode:

           3.1416        3.1416
          31.416         0.31416
         314.16          0.031416
       3 141.6           0.0031416
      31 416             0.00031416
     314 160             3.1416 e -5
   3 141 600             3.1416 e -6
  31 416 000
 314 160 000
           3.1416 e 9
           3.1416 e 10


This feature has been integrated into mainline but it isn't enabled in the official builds. If you'd like to try it, either get the sources, uncomment INCLUDE_SIGFIG_MODE in features.h and recompile the calculator, or download my precompiled binaries.

Many thanks to Bit for the work done on bringing the significant figures mode for the WP 34S and 31S up to date. Since (as Bit points out) it hasn't been included on very many calculators in the last forty years, I thought I'd just explain why I took the trouble to write it and why I like it so much.

First question: why limit significant figures at all on a calculator that can handle numbers with up to 37 or so digits? The answer is simple: I am a physics teacher, and when my students and I do experiments the quantities we measure are rarely known to more than 3 significant figures. I like being able to limit the digits displayed to a realistic number and that number is always much less than 12, let alone 37!

Second question: what's wrong with SCI or ENG mode? These modes do limit significant figures, but they also impose trailing zeroes and standard form. I do not like entering "2" and seeing it displayed as "2.00E00". This is partly because I like my calculator to do my work for me, but it's also nice to show my students calculated resistances, angles of refraction, volumes, pressures, densities (etc.) on the screen of my WP-34S to exactly 3 significant figures. My younger students (and some older ones too) who don't "get" powers of ten can then see what 3 s.f. means and that I practise what I preach (although, as yet, none have been persuaded to get a WP-34S for themselves!).

If you want to avoid standard form but still need trailing zeroes then SIG0 mode lets you do this. "2" is displayed as "2.00" in SIG0_2 mode.

This goes beyond teaching. Except when doing accounts or integer arithmetic, when can you really justify using more than 3 or 4 s.f.? Most of the digits in an answer are just noise. My calculator is nearly always set to SIG_2 or SIG_3 mode; everything looks so much neater and (nearly) every displayed digit means something. If you download a firmware versions that includes this feature, give it a try! You may find that you like it. Or not. But it's there if you ever want it.

Nigel (UK)
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RE: [34S & 31S] Unique display mode: significant figures - Nigel (UK) - 02-07-2015 10:13 PM



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