On Tue, 7 Apr 1998, Buell Smelt wrote:

> I'm thinking about building a calculator with a PIC for educational
> purposes.  I was hoping that people could give me their thoughts on a few
> points ( some of which are a bit off-topic [ you've been warned ] )...
>
> 1) I guess I'm looking for a collection of math routines.  I've run
> across a few on the web, but what eludes me is the theory of dealing with
> numbers bigger than 0xFF.

  There are LOTS of books on the subject.

  I personally recomend  Donald Knuth's "The Art of Computer Programming"
  (I forget which volume) which has a VERY good chapter on implementing
  multiple precision arithmatic.)

  Although nobody expects too much speed out of calculators... so you
  could even do it all as BCD...

> 2) LCD vs LED screen.  I'd like to go with a LCD, but I don't know if you
> can get small pic friendly LCDs.  They all seem big.
>
> Well I guess there really weren't any points, I was just hoping to hear a
> few peoples thoughts on what aproach they'd take.  Is it reasonable to try
> and make it a solar calculator?  How much code space would you guess I'd
> use.  What kind of keypad?  Any dialogue on this subject (hardware and
> software) would be welcomed (and beneficial to me).

  I don't have much to say on hardware... but I'm willing to (privately)
  discuss software implementation issues.

  Some things to think about:

     What functions?

     How much memory?
     Fixed size numbers?  How big?
     Mantissa,Exponent numbers?  What accuracy?

     Is it a flat expression evaluator, or does it
     do Polish Notation, or does it handle ()'s?

     Does it have just an input and working number,
     or does it have a stack, or does it have numbered
     registers, or does it have named registers?

     What do you do with errors?

>
> Thanks,
> Nathan Hendler
>