The least-significant digit, at the right.) (Carries could cause carries, so the carry process was sequential, starting at
This was followed by entering the carries, toward the end of the cycle.
Noting carries this phase was referred to as "digitation" by Friden. In the Friden and Monroe, the mechanism would alternately increment the accumulator by the count in the keyboard while In all three makes, the main driveshaft(s) would in such a case turn at a steady speed. If you held down the + bar on these machines, and set the keyboard not to clear at the end of the first cycle, the number contained in the keyboard would continuously add into the accumulator, and the counter dials would incrementīy one for each count. The others (as with at least some cash registers) had calculating parts that wentīack and forth the author knows little about these. Rotary calculators is that their internal calculating mechanism itself (as distinguished from "control" mechanism) rotated continuously. Burroughs and perhaps Victor might be among the principal U.S. The calculators I have in mind are referred to as "rotary" there are others, which I don't know much about. While other (primarily European) calculators operated according to these principles, their physical details might have differed. Once a multiplication was complete, the multiplier showed in these dials. Quotients (and in a few Friden models, square
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Except in the Monroe, there was a full carry/borrow. "cycle counter" aligned themselves with the active part of the machine only one dial was directly operated at once. As the carriage shifted, different dials in this "Add" cycles incremented the count, and "subtract" cycles decremented it. The carriage also had a second set of dials, which counted cycles of the machine. This set of dials was the accumulator, which showed products, sums, and differences. One cycle would add the number in the keyboard into the corresponding dials of the carriage, wherever it was positioned Ĭarries were done in the later part of the cycle. The main driveshaft (except in the later Marchants) turned once, and then the clutch disengaged. Pushing a key to do an operation unlatched a single-revolution clutch and started a governor-controlled "universal" motor, which was There was a number of keys to do various operations the + key was always prominent. Dials with numbers on them to show results showed through rectangular cutouts in the carriage cover. At the far (back) edge of the wedge was a carriage that was almost twice as wide as the main "wedge" it shifted back and forth primarily toĪccommodate the shifts required for multiplication and division. The keys were mounted on top of a wedge-shaped frame, with the machinery inside. This could be considered a "parallel-entry" keyboard, in the electronic sense. Zero is implicit, and need not be entered explicitly if that column is already clear. (editor's note: Nicholas is a former employee of several of the early mechanical/electro-mechanical calculator makers and considers himself a "lover of small precision mechanisms." We appreciate his insight into theĪll makes of calculators of this type known to the author (at least in the USA) had a "full" keyboard, which for a 10-digit machine, contains a 10 X 10 matrix of keys each digit has nine number keys, and a clear/zero key.