It was early in the seventeenth century that Napier, a native of Naples, invented the first actual mechanical means of calculating. He arranged strips of bone, on which were figures, so that they could be brought into various fixed combinations. The instrument was called "Napier's rod" or Napier's bones." It was the beginning of the slide rule, which has been found of invaluable aid to accountants and engineers.

One trouble with all these contrivances was that, although they aided man to figure, they offered no means of making a record of the work. The man who used these machines had no way of checking his work to know if it was right unless he did it all over again.

The first machine to perform multiplication by means of successive additions was invented by Leibnitz in the year 1671 and completed in 1694. It employed the principle of the "stepped reckoner." This model was kept first at Göttingen and afterward at Hanover, but it did not act efficiently, as the gears were not cut with sufficient accuracy. This was long before the days of accurate machine tools.

The first satisfactory calculating machine of this nature was that of C. X. Thomas, which was brought out about 1820. It is usually called the Thomas de Colmar Arithmometer. This Thomas type of machine, which is commonly known as the beveled gear type, is still in use today in modern business.