View source for Curta

{{short description|Mechanical pocket calculator}}
{{otheruses}}
{{Infobox calculator
|name=Curta
|image=File:Curta - National Museum of Computing.jpg
|alt=Curta Type II mechanical calculator
|caption=Curta Type II mechanical calculator
|type=[[Mechanical calculator]]
|manufacturer=Contina AG Mauren
|introduced=1948 (Type I){{br}}1954 (Type II)
|discontinued=1972
|invent-name=[[Curt Herzstark]]
|precision=11 digits (Type I){{br}}15 digits (Type II)
|invent-date=1930s
|display_size=6-digit revolution counter, 11-digit result counter (Type I){{br}}8-digit revolution counter, 15-digit result counter (Type II)
|cost=$125 (Type I){{br}}$165 (Type II)
|display_type=[[Mechanical counter]]|weight={{cvt|230|g|oz}} (Type I){{br}}{{cvt|360|g|oz}} (Type II)}}

[[File:Curta type I-CnAM 40092-IMG 6721-white.jpg|thumb|Curta Type I, on display at the [[Musée des Arts et Métiers]], Paris.]]
[[File:Curtadsasm.JPG|thumb|upright=1.8|A partially disassembled Curta calculator, showing the digit slides and the stepped drum behind them]]
[[File:Curta calculator.jpg|thumb|Curta Type I calculator, top view]]
[[File:Curta03.JPG|thumb|Curta Type I calculator, bottom view]]

The '''Curta''' is a hand-held [[mechanical calculator]] designed by [[Curt Herzstark]].<ref name="Stoll"/> It is known for its extremely compact design: a small cylinder that fits in the palm of the hand. It was affectionately known as the "pepper grinder" or "peppermill" due to its shape and means of operation; its superficial resemblance to a certain type of [[hand grenade]] also earned it the nickname "math grenade".<ref>{{cite magazine |date= September 2011 |title= ICES Insight |url= http://www.ices.dk/sites/pub/Publication%20Reports/ICES%20Insight/INSIGHTWEB2011.pdf#page=13 |publisher= International Council for the Exploration of the Sea |magazine= ICES Insight |volume= 48 |page= 13 |isbn= 978-87-7482-097-0 |accessdate= 25 August 2015 |archive-date= 3 March 2016 |archive-url= https://web.archive.org/web/20160303163943/http://www.ices.dk/sites/pub/Publication%20Reports/ICES%20Insight/INSIGHTWEB2011.pdf#page=13 |url-status= dead}}</ref>{{failed verification|date=April 2025}}

Curtas were considered the best portable calculators available until they were displaced by electronic calculators in the 1970s.<ref name="Stoll"/>

== History ==

The Curta was conceived by [[Curt Herzstark]] in the 1930s in [[Vienna]], [[Austria]]. By 1938, he had filed a key patent, covering his complemented stepped drum.<ref>{{patent|DE|747073|Rechenmaschine mit einer einzigen von Einstellrädchen umgebenen Staffelwalze [Calculating machine with a single staggered roller surrounded by setting wheels], filing date: 19 August 1938 (in German)}}</ref><ref>[https://patents.google.com/patent/DE747073C/en Google patent DE747073C] Calculating machine with a single staggered roller surrounded by setting wheels. Filing date: 19 August 1938 (in English)</ref> This single drum replaced the multiple drums, typically around 10 or so, of contemporary calculators, and it enabled not only addition, but subtraction through [[nines complement]] math, essentially subtracting by adding. The nines' complement math breakthrough eliminated the significant mechanical complexity created when "borrowing" during subtraction. This drum was the key to miniaturizing the Curta.

His work on the pocket calculator stopped in 1938 when the [[Nazi]]s forced him and his company to concentrate on manufacturing precision instruments for the German army.<ref name=":0">{{Cite web|url=http://newatlas.com/curta-death-camp-calculator/45506/?li_source=LI&li_medium=default-widget|title=Curta calculator: The mechanical marvel born in a Nazi death camp|website=newatlas.com|date= 12 October 2016 |access-date= 18 October 2016}}</ref>

Herzstark, the son of a Catholic mother and Jewish father, was taken into custody in 1943 and eventually sent to [[Buchenwald concentration camp]], where he was encouraged to continue his earlier research:

{{blockquote
| text=While I was imprisoned inside Buchenwald I had, after a few days, told the [people] in the work production scheduling department of my ideas. The head of the department, Mr. Munich said, 'See, Herzstark, I understand you've been working on a new thing, a small calculating machine. Do you know, I can give you a tip. We will allow you to make and draw everything. If it is really worth something, then we will give it to the Führer as a present after we win the war. Then, surely, you will be made an Aryan.' For me, that was the first time I thought to myself, my God, if you do this, you can extend your life. And then and there I started to draw the CURTA, the way I had imagined it.
| source=pp. 36-37<ref name="Quote">{{cite interview | last=Herzstark | first=Curt | interviewer=Erwin Tomash | publisher=Charles Babbage Institute, University of Minnesota | location=Minneapolis | type=Manuscript of Oral History Interview | lang=en,de | date=1987-09-10 | title=Oral history interview with Curt Herzstark | url=https://conservancy.umn.edu/handle/11299/107358 | pages=36-37}}<!-- See also, the transcript in German: https://conservancy.umn.edu/handle/11299/107359 --></ref> | author=Curt Herzstark | title=Oral history interview with Curt Herzstark (1987)
}}

In the camp, Herzstark was able to develop working drawings for a manufacturable device. Buchenwald was [[Buchenwald concentration camp#Liberation from Nazi Germany|liberated by U.S. troops]] on 11 April 1945, and by November Herzstark had located a factory in Sommertal, near [[Weimar]], whose machinists were skilled enough to produce three working prototypes.<ref name="Quote"/>

[[USSR|Soviet]] forces had arrived in July, and Herzstark feared being sent to Russia, so, later that same month, he fled to Austria. He began to look for financial backers, at the same time filing continuing patents as well as several additional patents to protect his work. [[Franz Joseph II, Prince of Liechtenstein]] eventually showed interest in the manufacture of the device, and soon a newly formed company, Contina AG Mauren, began production in Liechtenstein.

It was not long before Herzstark's financial backers, thinking they had got from him all they needed, conspired to force him out by reducing the value of all of the company's existing stock to zero, including his one-third interest.<ref name="Stoll">{{cite journal |author= Stoll, Cliff |authorlink=Cliff Stoll |title= The Curious History of the First Pocket Calculator |journal= Scientific American |volume=290 |issue=1 |pages= 92–99 |date= January 2004 |url=http://www.scientificamerican.com/article.cfm?id=the-curious-history-of-th |doi=10.1038/scientificamerican0104-92 |pmid= 14682043 |bibcode= 2004SciAm.290a..92S |url-access= subscription }}</ref> These were the same people who had earlier elected not to have Herzstark transfer ownership of his patents to the company, so that, should anyone sue, they would be suing Herzstark, not the company, thereby protecting themselves at Herzstark's expense. This ploy now backfired: without the patent rights, they could manufacture nothing. Herzstark was able to negotiate a new agreement, and money continued to flow to him.

Curtas were considered the best portable calculators available until they were displaced by electronic calculators in the 1970s.<ref name="Stoll"/> The Curta, however, lives on, being a highly popular collectible, with thousands of machines working just as smoothly as they did at the time of their manufacture.<ref name="Stoll"/><ref name="Quote"/><ref name="Kradolfer">{{cite web |url= http://www.vcalc.net/cu-bckup.htm#11 |title= Curt Herzstark and his Pocket Calculator Curta |first1= Peter |last1= Kradolfer |first2= Andries |last2= de Man |archive-url= https://web.archive.org/web/20220405095714/https://www.vcalc.net/cu-bckup.htm |archive-date= 5 April 2022}}</ref>

An estimated 140,000 Curta calculators were made (80,000 Type I and 60,000 Type II). According to Curt Herzstark, the last Curta was produced in 1972.<ref name="Quote" />

== Cost ==

The Curta Type I was sold for $125 in the later years of production, and the Type II was sold for $175. While only 3% of Curtas were returned to the factory for warranty repair,<ref name="Quote"/> a small, but significant number of buyers returned their Curtas in pieces, having attempted to disassemble them. Reassembling the machine was more difficult, requiring intimate knowledge of the orientation of, and installation order for, each part and sub-assembly, plus special guides designed to hold the pieces in place during assembly. Many identical-looking parts, each with slightly different dimensions, required test fitting and selection as well as special tools to adjust to design tolerances.<ref name="tools">[http://curta.li/05_anleitungen/57_curta_tools_main.html Several specialized Curta tools pictured at curta.li]</ref>

The machines have a high curiosity value; in 2016 they sold for around US$1,000, but buyers paid as much as US$1,900 for models in pristine condition with notable serial numbers.<ref name=":0" />

== Design ==

The Curta's design is a descendant of [[Gottfried Leibniz]]'s [[Stepped Reckoner]] and [[Charles Xavier Thomas|Charles Thomas's]] [[Arithmometer]], accumulating values on cogs, which are added or complemented by a [[Stepped Reckoner|stepped drum]] mechanism.

Numbers are entered using slides (one slide per digit) on the side of the device. The ''revolution counter'' and ''result counter'' reside around the shiftable carriage, at the top of the machine. A single turn of the crank adds the input number to the result counter, at any carriage position, and increments the corresponding digit of the revolution counter. Pulling the crank upwards slightly before turning performs a subtraction instead of an addition. Multiplication, division, and other functions require a series of crank and carriage-shifting operations.

== Models ==

The Type I Curta has eight digits for data entry (known as "setting sliders"), a six-digit revolution counter, and an eleven-digit result counter. According to the advertising literature, it weighs only {{convert|8|oz}}. Serial number 70154, produced in 1969, weighs {{convert|245|g}}.

The larger Type II Curta, introduced in 1954, has eleven digits for data entry, an eight-digit revolution counter, and a fifteen-digit result counter.<ref>{{cite web |last1=Toth |first1=Viktor |title=Programmable Calculators - Curta Type II |url=https://www.rskey.org/CMS/exhibit-hall/?view=article&id=120 |website=www.rskey.org |access-date=7 June 2024}}</ref>

== Uses ==

The Curta was popular among contestants in [[rallying|sports car rallies]] during the 1960s, 1970s and into the 1980s. 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 and so on, since the early electronic calculators did not fare well with the bounces and jolts of rallying.<ref name="Stoll"/>

The Curta was also favored by commercial and general-aviation pilots before the advent of electronic calculators because of its precision and the user's ability to confirm the accuracy of their manipulations via the revolution counter. Because calculations such as weight and balance are critical for safe flight, precise results free of pilot error are essential.

== Collections ==

The Curta calculator is very popular among collectors and can be purchased on many platforms. The Swiss entrepreneur and collector Peter Regenass holds a large collection of mechanical calculators, among them over 100 Curta calculators. A part of his collections is on display at the [[Enter Museum]] in [[Solothurn]], Switzerland.  In 2016 he donated a Curta calculator to the [[Yad Vashem]] Museum in Jerusalem. <ref>{{Cite web|last=Regenass|first=Peter|title=Hand-held calculator designed by Curt Herzstark from Vienna and completed while imprisoned in the Buchenwald camp|url=https://www.yadvashem.org/yv/en/exhibitions/bearing-witness/curta-calculator.asp|url-status=live|access-date=2021-07-02|website=Yad Vashem Museum Jerusalem|archive-url=https://web.archive.org/web/20210205151847/https://www.yadvashem.org/yv/en/exhibitions/bearing-witness/curta-calculator.asp |archive-date=2021-02-05 }}</ref>

== Popular culture ==
[[File:Curta Rechenmaschinen im Museum Enter Solothurn.jpg|thumb|The Curta collection of the Swiss entrepreneur Peter Regenass on display at the Enter Museum Solothurn]]

The Curta plays a role in [[William Gibson]]'s [[Pattern Recognition (novel)|''Pattern Recognition'']] (2003) as a piece of historic computing machinery as well as a crucial "trade" item.

In 2016 a Curta was designed by Marcus Wu that could be produced on a 3D printer.<ref name="Thingiverse">[https://www.thingiverse.com/thing:1943171  The 3D-Printed Curta Calculator] on [[Thingiverse]] ({{Webarchive|url=https://web.archive.org/web/20171012150442/https://www.thingiverse.com/thing:1943171 |date= 12 October 2017 }})</ref> The Curta's fine tolerances were beyond the ability of printer technology of 2017 to produce to scale, so the printed Curta was about the size of a coffee can and weighed about three pounds.<ref name="Popular_Mechanics">{{Cite web |date=2017-07-15 |title=Building a Gorgeous Mechanical Calculator With 3D-Printed Parts |url=https://www.popularmechanics.com/technology/gadgets/a27318/3d-printed-curta-calculator/ |access-date=2023-08-25 |website=Popular Mechanics |language=en-US}}</ref>

== Further reading ==
* {{Cite book |title=Kein Geschenk für den Führer&thinsp;: Schicksal eines begnadeten Erfinders |last=Herzstark |first=Curt |date=2005 |publisher=Books on Demand |isbn=3833411368 |location=Noderstedt |oclc=85361449 }}
* {{Cite book |url=http://www.oughtred.org/curta-book.shtml |title=The Inventor of the CURTA Calculator: Curt Herzstark, An Autobiography |date=2012 |publisher=Oughtred Society |isbn=9780979147760 |location=Roseville, Calif. |oclc=778199457 }}

== References ==
{{reflist}}

== External links ==
{{commons}}

* [http://vintagecalculators.com/html/curta_i.html Curta I] Vintage Calculators Web Museum:  Mechanical Calculators
* [https://web.archive.org/web/20110717153826/http://curta.org/ Curta.org]
* [http://www.vcalc.net/cu.htm The CURTA Calculator Page]
* [https://www.youtube.com/watch?v=loI1Kwed8Pk Video on internal workings of the Curta by MechanicalComputing]
* [http://www.curtamania.com/curta/code/home.html Home of www.curtamania.com] Many resources
* [https://www.curta.ch/index.php?mainPage=curta&subPage=&language=english http://www.curta.ch] Information about Curta / Video about the assembly of a Curta / Book about Curt Herzstark (Kein Geschenk für den Führer - Schicksal eines begnadeten Erfinders)
* [http://curta.li/ curta.li: model history, user and service manuals, parts photos, blueprints, etc.]
* [https://satadorus.eu/x_ite/yacs_2_0/yacs_2_0.html YACS-Yet Another Curta Simulator. A 3D Simulator in VRML]
* [http://curtamania.com/curta/code/type_and_age_of_your_curta.php Type and Age of your Curta]
* [https://www.thingiverse.com/thing:1943171 Files to 3D print a 3:1 scale model of a Curta]
* [https://www.curta.fr/ Curta.fr] Mainly focused on maintenance, repair and support. In french.
*{{cite journal |first=Herbert |last=Bruderer |title=Multiple Curtas |journal=Resurrection: The Bulletin of the Computer Conservation Society |issue=75 |date=Autumn 2016 |issn=0958-7403 |url=https://www.computerconservationsociety.org/resurrection/res75.htm#g}}
*{{cite journal |first=Herbert |last=Bruderer |title=A Multiple Curta |journal=Resurrection: The Bulletin of the Computer Conservation Society |issue=79 |date=Autumn 2017 |issn=0958-7403 |url=https://www.computerconservationsociety.org/resurrection/res79.htm#e}}

{{use dmy|date=July 2022}}
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