Origin of modern calculating machines

A technical chronicle traces the development of mechanical calculation from primitive counting aids through the inventions and patents that led to modern adding and accounting machines. It explains the mechanical principles behind key-driven and key-set recording devices, contrasts their intended uses, and details control mechanisms that enabled reliable multi-order operation. Illustrations and patent drawings accompany clear, non-technical descriptions of notable calculators, recorders, tabulators, and high-speed and billing devices. The author also discusses practical aspects of manufacture and operation and relates each machine to accounting practice, closing with reflections on the evolution of the art.