"the operation of machines of this type was accomplished by means of pulling levers or knobs to set up the desired number. addition, subtraction, multiplication, and division were accomplished by means of revolving drums. for addition they revolved in one direction, and for subtraction the direction was reversed. for multiplication the revolutions were repeated in the same direction as for addition, and for division they were repeated in the same direction as for subtraction. two sets of dials provided a means of reading totals. in one the accumulation of totals appeared; in the other, there appeared the figure which was added, subtracted, multiplied, or divided." (the office appliance manual, p. 88)