Curta

File:Curta.jpg

Curta mechanical calculator on display at the Computer History Museum in Mountain View, California.

A partially disassembled Curta calculator, showing the digit slides and the steppered drum behind them.

The Curta was a small, hand-cranked mechanical calculator introduced in 1948. It had a brilliantly 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 variant of Gottfried Leibnitz's Arithmometer, accumulating values on cogs, which are added or complemented by a stepped drum mechanism.

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

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 Type I Curta had 8 digits of slides, a 6-digit revolution counter, and a 11-digit result counter. 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.

The Curta was affectionately known as the "Pepper Grinder" due to its shape and means of operation. It would literally grind out answers.

Use in car rallies

The Curta was popular among contestants in sports car rallies during the 1960s, '70s and into the '80s. Even after the introduction of the electronic calculator for other purposes, they were used in time-speed-distance (TSD) rallies to aid in computation of times to checkpoints, distances off-course, etc.

Contestants who used such calculators were often called "Curta-crankers" by those who were limited to paper and pencil, or who utilized computers linked to the car's wheels.

The Curta in Fiction

The Curta is featured in the novel Pattern Recognition by William Gibson, where one of the minor characters has an interest in them.

External links

• The Curious History of the First Pocket Calculator by Cliff Stoll, Scientific American, January 2004
• A Shockwave-enabled simulation of the Curta
• Curta calculator fansite
• Curta.Org, Your Complete Curta Calculator Site includes a Wiki
• Curta Operating Manual. HTML coding by Andries de Man
• Curta site by Greg Saville
• The Amazing Curta by Bruce Flamm
• How to Calculate with a Curta by Nicholas Bodley
• Curta Handhelds at the Museum of HP Calculators
• Curt Herzstark and the Curta