Arithmometer

ARITHMOMETER (from the Greek arythmos - number and metron - measure), a calculating machine, belongs to the inventions of the 19th century (A. Thomas - 1820, W. T. Odhner - 1890). The arithmometer is currently an indispensable aid for elementary numerical manipulations, such as, for example, multiplication and division of multi-digit numbers, calculation of percentages, etc. Using the apparatus is very simple and accessible to everyone. The apparatus consists of the following parts: a) a rotating (calculating) drum, covered by a fixed case (A in the figure) with slots through which the movable pins of the drum protrude: each slot of the case corresponds to a numerical order (units, tens, hundreds, etc.); each movable pin can be set to any digit (from 0 to 9); b) the indicator part of the box with two rows of openings - large ones, where the digits show the results of the calculation (sum, difference), and small ones (on the left), where the digits correspond to the number of drum rotations (and at the same time show the multiplier, quotient). Auxiliary parts of the device: c) the drum handle (B in the figure), rotating it in one direction for addition and in the other for subtraction; d) a button in the middle of the box (D in the figure); when pressed, it is possible to move the box (along internal rails) to the right and left; e) levers, right and left (CC in the figure) for clearing the digits of the indicator box. All these parts are tightly connected to each other and form a massive device on a convenient stand. Work on the apparatus consists of the following moments: 1) for addition - the addend is initially set on the movable pins of the drum and then, by rotating the drum in the plus (+) direction, is transferred to the indicator row of the box; in the same order, the second addend follows the first, etc. - the sought sum is mechanically formed in the indicator row of numbers; 2) for subtraction - the minuend is first set on the pins and in the indicator row

the subtrahend,

is set on the pins,

by rotating the drum

in the minus (-) direction, and the sought difference is obtained in the indicator row; 3) multiplication is performed by the type of addition: the multiplicand is set on the pins and then - in the indicator row as many times as there are units in the multiplier + how many tens + how many hundreds, etc.; at the same time, when multiplying by tens, the indicator row (by moving to the left by one position when pressing the button) is placed under the tens, by two positions - under the hundreds, etc.; at the end of the manipulation, the indicator row gives the sought product, and the left row (small digits) shows at the same time the multiplier used; 4) division is performed by the type of subtraction: the dividend is set on the pins and transferred to the indicator row; then the divisor is set on the pins, after which it is sequentially subtracted from the dividend by rotating the drum in the minus direction, starting from the highest order to the lowest; the small digits of the left row will show the digits of the quotient; 5) calculation of percentage ratios is performed by the type of division. Necessary precautions during work: all auxiliary parts - the drum handle, both levers, the button - must, after each manipulation with them, fit tightly into their grooves, where they are held by a spring.