[34S & 31S] Unique display mode: significant figures

[Bit]

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.



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.