LOG for HP 12C - Printable Version +- HP Forums ( https://www.hpmuseum.org/forum)+-- Forum: HP Calculators (and very old HP Computers) ( /forum-3.html)+--- Forum: General Forum ( /forum-4.html)+--- Thread: LOG for HP 12C ( /thread-8934.html) |

LOG for HP 12C - Gamo - 08-30-2017 01:47 AM
Here is a LOG program for HP 12C Find the LOG in any base of any number: LOGь X: X > 0, b > 1 01 LN 02 R↓ 03 LN 04 R↓ 05 R↓ 06 R↓ 07 ÷ 08 GTO 00 Example: LOG₃ 9 = 2 9 ENTER 3 R/S 2 LOG₈₁ 3 = ⅟₄ 3 ENTER 81 R/S 0.25 LOG₁₀₀₀ 10 = ⅓ 10 ENTER 1000 R/S 0.33 Gamo RE: LOG for HP 12C - Gerson W. Barbosa - 08-30-2017 02:07 AM
Here is my version. Not exactly faster, better or more accurate, only three steps shorter: 01 LN 02 1/x 03 y^x 04 LN 05 GTO 00 Best regards, Gerson. -------- PS: Or, in a more conventional way, but one step longer: 01 LN 02 x<>y 03 LN 04 / 05 1/x 06 GTO 00 RE: LOG for HP 12C - Gene - 08-30-2017 02:07 AM
EDIT: Rats, Gerson was faster and shorter. :-) Is either method more accurate? Good idea! How about: LN X<>Y LN X<>Y / GTO 00 RE: LOG for HP 12C - Gerson W. Barbosa - 08-30-2017 02:20 AM
(08-30-2017 02:07 AM)Gene Wrote: How about: Better than my 6-step version above (register swap is faster than 1/x). Faster than the 5-step one too! Gerson. RE: LOG for HP 12C - Gamo - 08-30-2017 04:22 AM
Thanks for more alternative ways of LOG program. Just wondering about the compute functions like 1/x or y^x will take more time to calculate than just using Rv or X<>Y Gamo RE: LOG for HP 12C - Gerson W. Barbosa - 08-30-2017 02:42 PM
(08-30-2017 04:22 AM)Gamo Wrote: Just wondering about the compute functions like 1/x or y^x will take more time to calculate than just using Rv or X<>Y Rv and x<>y are simple operations involving transfer of contents between internal registers. y^x alone requires a call to LN and another to e^x, both transcendental functions that take a lot a shift and add operations plus access to external tables in ROM. On slow calculators like the original HP-12C the difference in speed is quite noticeable, even without a stopwatch. The choice of which solution to use depends on what amount of free memory you have. The five-step version would make sense if those were the last remaining free steps on you 12C. Gerson. |