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Dehomag was a German subsidiary of IBM with monopoly in the German market before and during World War II. The word was an acronym for Deutsche Hollerith-Maschinen Gesellschaft mbH (English: German Hollerith Machines LLC). Hollerith refers to the German-American inventor of the technology of punched cards, Herman Hollerith.
Under Nazi Germany, Dehomag leased and maintained the Nazis' collection of card punch machines. The use of this technology increased the efficiency of the Final Solution. IBM in New York established a special subsidiary, Watson Business Machines, to deal with railway traffic in the General Government during the Holocaust in Poland. The German Transport Ministry used IBM machines under the New York-controlled subsidiary in Warsaw, not the German subsidiary. Dehomag general manager for Germany, Hermann Rottke, reported to Thomas J. Watson in New York. It was legal for IBM to service the Third Reich directly, but only until America entered the war in December 1941.
The technology of punched cards dates back at least to the 18th century when it was used for mass production of woven textiles and later used as a recording and play back system in player pianos. The use of punched cards for recording and tabulating data was first proposed and used by Semen Korsakov in or about 1805. In 1832 Charles Babbage proposed using similar cards to program and store computation by his calculating engine. Punch card technology was further developed for tabulating and data processing purposes by Herman Hollerith, dated back to the 1880s. It was used for the 1890 United States Census and for the census work of several foreign governments. Willy Heidinger, an acquaintance of Hollerith, licensed all of Hollerith’s patents in 1910, and created Dehomag in Germany. In 1911 Hollerith's company merged with several others, forming Computing Tabulating Recording Company (CTR). In 1923 CTR acquired 90% ownership of Dehomag, thus acquiring patents developed by them. In 1924 CTR was renamed IBM.
In the following years, Dehomag, obeying the direct orders of IBM and Thomas J. Watson, became the main provider of computing expertise and equipment in Nazi Germany. Dehomag gave the Nazi party the means for a large census of the population and for searching its data.
 See also
- Edwin Black on IBM and the Holocaust
- Aspray (ed.), William (1990). Computing Before Computers. Iowa State University Press. p. 137. ISBN 0-8138-0047-1.
 Further reading
- Black, Edwin (2001). IBM and the Holocaust: The Strategic Alliance between Nazi Germany and America's Most Powerful Corporation' ISBN 0-609-60799-5
- Anita Ramasastry. A Swiss court allows Gypsies' Holocaust lawsuit to proceed. CNN, 2004-07-08.
- Dehomag D11 tabulation machine exhibit in the United States Holocaust Memorial Museum