realtids

Realtids refers to the property of a system or process where the correctness of its operation depends on the timeliness of its responses in addition to the correctness of its outputs. In real-time contexts, actions must occur within predefined time constraints or deadlines.

Real-time systems are categorized by deadlines. Hard real-time systems must never miss a deadline; failure to meet timing requirements can have severe or catastrophic consequences. Soft real-time systems aim to complete tasks within deadlines most of the time, with performance degrading if some deadlines are missed. Firm real-time systems allow occasional misses but still enforce upper bounds on lateness.

Key aspects include determinism, low and bounded latency, and guarantees about timing. Real-time operating systems (RTOS) provide scheduling policies designed to meet deadlines, such as fixed-priority (rate-monotonic) or dynamic priority (earliest-deadline-first). Engineers perform timing analysis to estimate worst-case execution time (WCET) and ensure it fits within deadlines. Real-time data processing often relies on streaming and event-driven architectures to minimize latency.

Common domains for real-time applications include embedded control in vehicles and aircraft, industrial automation, robotics, medical devices, and telecommunications. In finance, ultra-low-latency processing for trading is also described as real-time, though it is governed by strict regulatory and market-structure considerations.

Real-time challenges include resource constraints, concurrency, synchronization, fault tolerance, and verification. Real-time systems distinguish timing correctness from functional correctness, requiring design, testing, and often certification to ensure predictable behavior under all operating conditions.