(11C) (15C) Very fast binary converter + fast modulo

[johnb]

(03-17-2018 09:17 PM)Dieter Wrote:  From your blog post I understand that all this is new to you and something like ..."vintage computing", while most of the members here have grown up with all this, and RPN is nothing that one even has to think about – it feels natural and intuitive. ;-)

(03-18-2018 12:14 AM)Michael Zinn Wrote:  Yes, I see this as a fun vintage computing experience. I wanted to try something that was new to me and solving problems by programming the calculator is an interesting puzzle (It's very far removed from high level languages like Haskell or even Java).

I think most if not all of us here find this a laudable goal. At some point, to someone, *everything* becomes a vintage computing experience... there's a prof at Drexel University whom I follow, who is probably currently the world's foremost expert on programming the ENIAC! Now that's vintage!!

(03-17-2018 06:06 PM)michaelzinn Wrote:  Also, how exactly are numbers stored in registers? The app I'm using might be inaccurate here, do real HP calculators use decimals with a floating point? Or is it binary?

(03-17-2018 09:17 PM)Dieter Wrote:  No, it's decimal arithmetics (BCD). The internal registers consist of 7 bytes = 56 bits with one nybble (4 bits) for each digit in mantissa (10) and exponent (2), and two more for their respective signs.

There's another prof, this time at Auburn University, who has successfully instituted a policy that you don't graduate there with a CS degree without doing at least a one semester project implementation on "old iron," i.e. a vintage computer with an architecture unlike most current architectures.

Too many software engineers who grew up on Intel CPU chips assume that every digital computer has always been:
* binary
* two's complement
* little-endian
* "reals" represented by "mantissa & exponent" floating point
* hardware-implementation of subroutine call stack
* protected memory
etc...

The long road of computing development is far more interesting than that, however, and it's fascinating to sometimes find remnants of that in calculators or other interesting pieces of hardware!

(Yes, there have been machines that did base-10 in hardware (ENIAC was one!), or used one's complement or even weirder representations; fixed-point approximations of reals; other formats such as numerator/denominator; no hardware stack; no "call" or "return" instructions; flat address space; weird multiple address spaces; et cetera.)