SoftwareTimer

Software timers are timer mechanisms implemented in software by an operating system or application, used to schedule actions to execute after a specified delay or at regular intervals. They rely on the system clock or a tick interrupt rather than dedicated hardware timers and are typically managed by a timer subsystem or event loop.

How they work: The timer subsystem maintains one or more timer entries with target expiration times and associated callbacks. On each clock tick or in an event loop iteration, expired timers are identified and their callbacks are invoked. Timers can be configured as one-shot (firing once) or periodic (repeating at a fixed interval). They can also be relative (delay from now) or absolute (specific timestamp).

Implementation considerations: Precision and jitter depend on the resolution of the system clock and the scheduling granularity of the host. In real-time or embedded environments, software timers are often backed by a timer queue or a dedicated timer task, and may cooperate with a hardware timer for better accuracy. In general-purpose systems, the timing accuracy is sufficient for UI timeouts or network retries but may be inadequate for hard real-time requirements.

Advantages and limitations: Software timers offer portability, flexibility, and lower hardware requirements. They are easy to extend and integrate with higher-level software. Drawbacks include CPU overhead, potential jitter, and limited determinism compared with hardware timers, particularly under heavy load or multitasking systems.

Applications: They are widely used for user interface timeouts, debouncing input, protocol timeouts, retry schedules, animation timing, and background maintenance tasks. In embedded and real-time systems, software timers are often part of a broader timer framework that also includes watchdog and deadline mechanisms.