10E500?

[cyrille de brébisson]

Hello,

Prime uses the math library which was first developed for the HP71 in the early 80's!
the HP71 had CPU registers of the form:
4 bit: s
12*4 bits: m
12 bits: x

for a total of 64 bits.
s was used for the sign (including special encoding for infinite)
m was a 12 digit BCD mantissa...
x was a BCD signed number for the exponent... due to the sign and BCD encodding, this limited the exponent to the -500/+499 range...
Why did they decide to use BCD and not binary (which would have provided exponents all the way to 2048, I do not know)...

The math algo were reused in Prime. the same limits were put in place, even as we now have 32 bits to store the exponent because, we do trust the library and the also as is, but we do not know/have no certainty that they would work well if the exponents were increased...

Sure, basic operations would have no problems. But things such as sin when x is very small (and x could get a whole lot smaller with larger exponents) might prove problematic....

The other issue is the CAS.
The CAS uses 64 bit IEEE floats. These are limited to an exponent +/-308! this difference between CAS and non CAS already causes issues for some users in placed. increasing the exponent would just exacerbate the problem.

So, here you go. sorry about that, but this does put a limit on what you can do with the calculator...

cyrille