On Thu, 20 Jul 2006, Sidney Cammeresi wrote: > On Thu, 20 Jul 2006 at 01.35.03 -0500, Chuck Cole wrote: > >> Several kinds of applications require more than 8 digit precision. HP >> calculators are the only ones that have at least 10 digits of precision >> throughout. We could not use TI scientific calculators except as slide >> rule replacements because of their 8 digit limited precision. >> Discovering that 8 digits was not enough at all in these applications >> made a deep impression on me. > > Ten digits on a slide rule? How exactly does that work? Given that a > normal ten-inch slide rule has three digits of precision throughout the > scale (four on the left side, blah blah), you'd need a slide rule 106 > feet long to get ten digits. I don't know how much precision a > five-inch pocket slide rule has, so maybe I'm off buy one factor of two. > > `Three digits is enough for most things' was the slide rule mantra. He was only saying that 8-digits is enough for "slide rule replacement", which makes sense because if a slide rule can do three digits, then a device that can do 8 digits is more than sufficient to replace a slide rule. I would like to hear from Chuck what he was doing that required 10 digits instead of 8 digits. That's pretty interesting. I'd also wonder about internal precision because I believe my old calculator that showed 8 digits actually had a little more inside and you could see those extra digits by subtracting away the 8 visible digits. It would then show a few in scientific notation. Hypothetical example: 0.83248872 -0.83248872 ---------- 3.17 E-09 Mike