HP-25/SR-56 Identical Conditionals

[Valentin Albillo]

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Hi, Gene:

(10-12-2021 03:05 PM)Gene Wrote:  The SR-56, having 100 unmerged steps, which is admittedly more actual memory in practice than the HP-25, [...]

This has been discussed here a decade or two ago. 100 unmerged steps aren't necessarily "more actual memory" than 49 fully-merged ones, in practice, only marginally if at all.

What results in "more actual memory" in practice is that the SR ("Slide Rule", LOL !) 56 has subroutine capability and this really, really saves steps, a lot in many frequent cases. Think Runge-Kutta 4th order, which requires four calls to f(x,y), or even just Newton's method to solve f(x)=0, which requires two calls to f(x), or Hallery's method, which requires three. As soon as f(x) or f(x,y) isn't trivial, you'll be saving both programming complexity and steps by the truckload.

I remember back then (45 years ago !), that I was *very* tempted to sell my HP-25 and buy the SR-56 (despite me strongly disliking anything algebraic vs. RPN) just because of that subroutine capability, that I saw as essential and upping the calculator to a higher level. Fortunately the HP-67 was introduced, with several levels of subroutines (and lots more) and that saved me from falling for AOS. The horror, the horror !

Also, the SR-56 had some looping construct (DSZ, IIRC), but that was far less important to me.

Best regards.
V.