Editing Curta (section)

== 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" />