Editing Tabulating machine (section)

==Operation==
{{main|Plugboard}}
[[File:Early SSA accounting operations.jpg|thumb|IBM Type 285<ref>{{cite web |website= Columbia University Computing History |title = The IBM 285 Tabulator |url= http://www.columbia.edu/cu/computinghistory/285.html |first =  Frank |last =da Cruz|date= 16 December 2018}}</ref> tabulators in use at U.S. Social Security Administration circa 1936]]
[[File:IBM D11 (early Tabulation Machine).jpg|thumb|Early IBM D11 tabulating machine, with covers removed]]
[[File:Powers-Samas accounting machine.jpg|thumb|Powers-Samas accounting machine]]
In its basic form, a tabulating machine would read one card at a time, print portions (fields) of the card on [[fan-fold paper]], possibly rearranged, and add one or more numbers punched on the card to one or more counters, called [[Accumulator (computing)|accumulators]].  On early models, the accumulator register dials would be read manually after a card run to get totals. Later models could print totals directly. Cards with a particular punch could be treated as master cards causing different behavior. For example, customer master cards could be merged with sorted cards recording individual items purchased. When read by the tabulating machine to create invoices, the billing address and customer number would be printed from the master card, and then individual items purchased and their price would be printed. When the next master card was detected, the total price would be printed from the accumulator and the page ejected to the top of the next page, typically using a [[carriage control tape]].

With successive stages or cycles of punched-card processing, fairly complex calculations could be made if one had a sufficient set of equipment. (In modern data processing terms, one can think of each stage as an [[SQL]] clause: SELECT (filter columns), then WHERE (filter cards, or "rows"), then maybe a GROUP BY for totals and counts, then a SORT BY; and then perhaps feed those back to another set of SELECT and WHERE cycles again if needed.) A human operator had to retrieve, load, and store the various card decks at each stage.