Genaille

Genaille is a French surname. The best-known association with the name in mathematics and computing is the Genaille–Lucas rulers, a set of mechanical calculating rulers devised in the late 19th century by Édouard Lucas and Louis Genaille. The rulers consist of a stack of sliding strips, each corresponding to a digit position, which can be arranged to perform multiplication and division. A distinctive feature is a built-in carry scheme: each ruler includes a fixed table that encodes carries, enabling the user to read the final result directly from the top of the stack rather than performing intermediate steps. The Genaille–Lucas system was intended as a practical aid for arithmetic and as an example of early computing technology. Although it never achieved widespread commercial use, the device is regarded as an important milestone in the history of calculating machines and has been the subject of reproductions, reconstructions, and museum displays. Today, Genaille-Lucas rulers are studied by historians of computing and mathematical instrumentation.