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Napier's bones is a manually operated calculating device created by John Napier of Merchiston, Scotland for the calculation of products and quotients of numbers. The method was based on lattice multiplication , and also called rabdology , a word invented by Napier.
The promptuary contains a lot more pieces than a set of Napier's Bones. A set of Napier's Bones with 20 rods is capable of multiplying numbers of up to 8 digits. An equivalent promptuary needs 160 strips. In the examples and illustrations below, N is set to 5 - that is, the illustrated promptuary can multiply numbers of up to 5 digits.
The first device, which by then was already popularly used and known as Napier's bones, was a set of rods inscribed with the multiplication table. Napier coined the word rabdology (from Greek ῥάβδος [rhabdos], rod and λόγoς [logos] calculation or reckoning) to describe this technique. The rods were used to multiply, divide and even ...
The pocket-sized Hewlett-Packard HP-35 scientific calculator was the first handheld device of its type, but it cost US$395 in 1972. This was justifiable for some engineering professionals, but too expensive for most students. Around 1974, lower-cost handheld electronic scientific calculators started to make slide rules largely obsolete.
Binary notation had not yet been standardized, so Napier used what he called location numerals to represent binary numbers. Napier's system uses sign-value notation to represent numbers; it uses successive letters from the Latin alphabet to represent successive powers of two: a = 2 0 = 1, b = 2 1 = 2, c = 2 2 = 4, d = 2 3 = 8, e = 2 4 = 16 and so on.
Included are function tables of logarithms (a useful computational tool that had been described in 1614 by John Napier) and antilogarithms, and instructive examples for computing planetary positions. [7] For most stars these tables were accurate to within one arc minute, [8] and included corrective factors for atmospheric refraction. [9]
Pascal tried to create a smoothly functioning adding machine for use by his father initially, and later for commercialisation, while the adding machine in Schickard's design appears to have been introduced to assist in multiplication (through the calculation of partial products using Napier's bones, a process that can also be used to assist ...
The device is a variant of Napier's bones. By representing the carry graphically, the user can read off the results of simple multiplication problems directly, with no intermediate mental calculations .