Guess what I found

Den mandag den 23. februar 2015 kl. 00.41.51 UTC+1 skrev John Larkin:

up till the last few years of uni I used one of these:

Then I got one of these:

these days I use google for the simple stuff and matlab for the rest, scripting, a proper keyboard and editing just makes things so much easier

-Lasse

the first link I gave is free web acess. You should have entered your question, and just watch what happens.

I bought the app based on a query about satellites, which it promptly found and expounded on.

If you want to multiply by a number >1 then it can be left-shifted before or after (or both), so a multiply by 1.8 could be a multiply by two and a fractional multiply by 0x7333 3333

Best regards, Spehro Pefhany

Den mandag den 23. februar 2015 kl. 03.40.03 UTC+1 skrev Spehro Pefhany:

that would be a strange fractional notation, normally

but that also means you have risk of overflow in multiplications*, because of -1*-1 = +1

Q1.31 * Q1.31 = Q2.62

-Lasse

You're absolutely right- I mispoke. 0x80... is exactly -1.

Best regards, Spehro Pefhany

I used to do that a lot, but now I have an embedded system programmer, and it's hard to explain this sort of math, and we use ARMs with hardware FP, so we do most everything in floats now, just clip and scale to ints at the very end.

Yes.. same here, but unfortunately the FPUs in the ARMs I've used are only single precision and 24 bits of precision won't always cut it.

I think you have to go to an ARM9 or better to get an option of double precision.

Best regards, Spehro Pefhany

there's sixteen candidates, none of them work.

If your allowed to reorder the left side 

Me, too. But not back in 1979 which was when I used the HP-25.

In 79, I was running a PDP11 timeshare system, with Basic+. You could run a *300* line program!

You probably didn't carry it around with you as I did with the HP-25.

That theme again.

Apparently it is on an HP16.

I used to use a thing I called Zform, which is 64 bits 2's comp, S32.32. It will handle most any real-world engineering units. I wrote a saturating (exception-free) math package in assembly for the 68K. Some operations, like Z-to-int and adds are easy. No normalizations are needed for those, which saves a lot of hassle. The divide was the nuisance.

It had a room of its own, with a line printer and an operator!

Fields has never heard of integer arithmetic or rounding. No surprise.

Since you have the app, I would have thought you could tell us if it worked.

Counting binary places is exactly what I did *not* want to do (but was forced to anyway).

By '79 I was running on MVS, VM, and VS. For a programmable calculator, I used APL. ;-) Graphics, too (19" Tektronix storage tube).