counters

A counter is a device, mechanism, or data structure that records the number of times a specific event occurs or a value is reached. Counters are used in mathematics, engineering, computing, and everyday measurement.

Mechanical counters are manual devices with rotating wheels that advance on each event. They include tally counters and odometers, providing a physical record of counts without electronic components.

Digital counters are circuits that update a numeric value in response to input pulses. Common types are up counters, down counters, and up/down counters. They may be binary, decimal (BCD), or other bases, and can be modulo-n to reset after a fixed count.

In software, counters are variables or data structures that tally occurrences, track frequencies, or control loops. They require careful handling in concurrent contexts to avoid race conditions, often using atomic operations or synchronization.

Common considerations include overflow, reset behavior, debouncing for mechanical inputs, and carry logic in arithmetic applications. Counters form parts of timing circuits, frequency dividers, event trackers, and basic components of finite-state machines.