The smaller register above it counts the turns. Subtraction is achieved by turning the crank in reverse. To multiply the Repeat button is pressed and the crank turned as often as needed for the low-order digit. Then the carriage is moved to the right with the handle in front, so the next digit of the factor can be cranked in. The crank on the carriage is for resetting result and counter registers.
Division is performed by subtracting the divisor left to right.
Courtesy of Gio Wiederhold. Marchant Electric Calculator, ca. This calculator was used by Prof. George Forsythe, founding chairman of the Stanford Computer Science department. Selection one of 10 keys on the right side determines the number of turns for multiplication. Division was automated by entering the divisor in the keys and continuing subtraction until the the dividend was fully reduced.