 Finding the number of digits on the iPhone Calculator - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: Not HP Calculators (/forum-7.html) +--- Forum: Not remotely HP Calculators (/forum-9.html) +--- Thread: Finding the number of digits on the iPhone Calculator (/thread-14033.html) Finding the number of digits on the iPhone Calculator - TheKaneB - 11-22-2019 04:06 PM Hi, I'm trying to figure out the number of internal digits used in the iPhone standard Calculator App but I'm not sure I'm doing it right. By calculating 1/3 and removing all the visible digits I start seeing weird results after the 20th digit or so. I guess it's an artifact caused by the binary representation? Is there a way to infer the exact number of binary digits used? I guess it's 64 bits but I want to be able to test my guess. Any help appreciated! Thanks! RE: Finding the number of digits on the iPhone Calculator - Albert Chan - 11-22-2019 05:47 PM Try to find eps, such that eps + 1 - 1 = 0 For example, my ipad Sci:Pro Calc apps has 128 bits precision Code: ```2 ^ -127 + 1 - 1 = 5.877471754111438e-39 2 ^ -128 + 1 - 1 = 0``` Update: it is safer to double check around found eps, since 1+eps is a half-way case. 3e-39 + 1 - 1 → 5.877471754111438e-39 2e-39 + 1 - 1 → 0 RE: Finding the number of digits on the iPhone Calculator - TheKaneB - 11-22-2019 06:36 PM nice trick, thank you! Using this method it turns out it's 64 bit precision 