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CURTA Mechanical Calculator

Comments

The Curta was a small, hand-cranked mechanical calculator introduced in 1948. It had an extremely compact design, a small cylinder that fit in the palm of the hand. It could be used to perform addition, subtraction, multiplication, division, and, with more difficulty, square roots and other operations. The Curta's design is a descendant of Gottfried Leibniz's Stepped Reckoner and Thomas's Arithmometer, accumulating values on cogs, which are added or complemented by a stepped drum mechanism.

The inventor

The Curta was invented by Curt Herzstark while he was a prisoner in the Buchenwald concentration camp. Following the end of WWII he completed and perfected the design. They were made in Liechtenstein by Contina AG Mauren. They were widely considered the best portable calculators available, until they were displaced by electronic calculators in the 1970s.

Description and use

Numbers were entered using slides (one slide per digit) on the side of the device. The revolution counter and result counter appeared on the top. A single turn of the crank would add the input number to the result counter, at any position, and increment the revolution counter accordingly. Pulling the crank out slightly before turning it would perform a subtraction instead of an addition. Multiplication, division, and other functions required a series of crank operations. The Curta was affectionately known as the "pepper grinder" or "peppermill" due to its shape and means of operation.

Curta Types I and II

The Type I Curta had 8 digits of slides, a 6-digit revolution counter, and an 11-digit result counter. According to the advertising literature, it weighs only 8 ounces (about 230 grams). The larger Type II Curta, introduced in 1954, had 11 digits of slides, an 8-digit revolution counter, and a 15-digit result counter.

An estimated 140,000 Curta calculators were made (80,000 Type I and 60,000 Type II). The last Curta was produced in November, 1970.