A mechanical device for storing a number from 0 to 9. Devices such as these were often attached to the desks of engineers, as part of historical “desktop computers.”
Each wheel can stably rest in any one of ten states. Digit wheels are often useful when it comes to thinking about how much data a physical object can store, as they were physical objects that were clearly designed for storing data. See also Data capacity.
Mathematics is the study of numbers and other ideal objects that can be described by axioms.