In 1642 Blaise Pascal (1623-1662) invented a calculating machine he hoped would be of assistance to his father in the performance of his duties as a tax officer. Pascal's machine used a series of stylus operated wheels which were interconnected so that each wheel advanced one number when its neighbor to the right made a complete revolution. The wheels turned in both directions to handle addition and subtraction. In 1647, five years after the first machine had been developed, Pascal obtained a patent for his device, which has been accepted traditionally as the first geared digital computer.