Digital Slide Rule4.06.08 - App Store

The slide rule was used for over 400 years as a calculating/estimation tool. Abandoned with the advent of hand-held calculators, computers and smart phones, their elegant simplicity is still a thing of wonderment. This program replicates the most common types of slide rules: Straight, circular, spiral and cylindrical. Dozens of scales are included and numerous features that could never exist on a physical slide rule are also included, such as color options, numeric displays of the values under the hairlines, and so on.
Slide rules were used to go to the moon and to build bridges, skyscrapers, tunnels, aqueducts and nearly everything else. Slide rules were simple to use and accurate enough for most occasions.

Also, note that this program is processor-intensive and with heavy use, will probably drain your battery quickly. Every effort has been make the program efficient, but nevertheless, some functions take a few moments to occur, including initial load, which can take three or four seconds, or perhaps a little longer. Nearly 30,000 "nibs" are created during this time, as well as over 3,000 labels, so please be a little patient! Because of all the detail, it looks best and runs best on a large-format machine such as a tablet. Also because of all the detail, the 30-loop spiral slide rule converts to a low-rez "bitmap data image" while you move it, then back to a "vector based image" as soon as you release.

Includes a brief side show slide show of famous and interesting slide rules, most of which are in the author's collection. Two are public-domain photographs of antique slide rules.

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Notes on usage: Program features include "two-finger pinch/zoom." Slide rule slide show images can also be rotated. Enlarge an image by double-tapping in the same place. Tapping three times in the same place will return the program to the home position. Tapping four times will bring up an intro-screen message which requires tapping anywhere to remove.

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This program was first released in 2016 and is the product of a lifelong love of numbers (and 30+ years of programming experience!).

Special thanks to the Oughtred Society for their member's invaluable help in evaluating the earliest versions of this program.

Version History Faster setup time after program is loaded (as much as 50% faster); streamlined internal processing (especially of Cylindrical Slide Rule); corrected "Display Estimated Hairline Values" for several of the alternate scales. 4.06.08 10/30/2017 Items can be enlarged separately for faster response times. A rotating fine adjust button added (hold finger over slide or hairline for a few seconds to use). Several add'l old slide rules added, including a circa 1962 Nuclear Bomb Effects Computer. Digital 10-loop spiral added. Many minor enhancements, mostly for speed improvements. Uses occasional interstitials instead of banners, except for the first few minutes when small banners for our other programs are shown. 3.30.08 07/29/2017 Added 9 new scales designed by Istvan Szalkai
Minimum frame rate now 0.05 f.p.s. for iOS devices. Shortened time before going to minimum frame rate to save battery power.
Improved alignments of nibs at alignment points. Improved alignment of colorized nibs.
All descending scales now colored red.
Animated many scales in opening screen and in slide rule slide show.
Added buttons to rotate scales in slide show.
Added more environment info to settings box, added gear in upper right now brings box up.
Allowed straight slide rule upper and lower hairlines and slides to be moved separately if desired (use lock/unlock button on right lower slide to turn lockstep off/on)
Added display of hairline values when values display active and slide(s) are moved (not just when hairline is moved)
Added animation from Eadweard Muybridge's 1800s photographs when author name in title is clicked.
Other minor fixes. 2.56.90 04/28/2017 Now includes a learning slide rule with just five scales on it: A, B, C, D and CI, along with instructions for several basic mathematical operations: multiplication, division, squares and square roots. 1.74.16 10/24/2016 1.72.12 05/25/2016