Until the discovery of the Antikythera Mechanism, astrolabes were often considered the earliest analog mathematical devices. Such complex gearwork as in this astronomical calculator, however, only appeared (again) much later, especially in medieval clockworks. Leonardo da Vinci (1452–1519) knew gears, as his drawings show. Heron of Alexandria (1st century) used cogwheels for his pantograph. The construction of analog measuring and drawing instruments (for example, sectors, proportional dividers, compasses) and logarithmic circular and cylindrical slide rules was comparatively simple. Planimeters and (mechanical) differential analyzers were sophisticated. The first mechanical calculating machines were invented in the 17th century (Wilhelm Schickard, Blaise Pascal, Gottfried Leibniz). These digital devices required stepped drums, pinwheels, and accumulators. In the second half of the 20th century there was a competition between electronic analog computers and electronic digital computers.
This article is not about new groundbreaking insights. Rather, it presents an overview of decades of effort and different views. The review is not aimed at experts, but at computer scientists who are interested in the history of technology.