A real-time system is a computer system that must react to events within a defined time limit - correctness alone is not enough; results must arrive on time. These systems are typically classified as hard, firm, or soft real-time depending on how catastrophic a missed deadline would be.
Real-time technology is used in everything from pacemakers and aircraft control systems to audio/video playback and industrial automation. They often rely on real-time operating systems (RTOS) such as FreeRTOS, Zephyr, or RTEMS, which offer deterministic scheduling and predictable response times. Some real-time systems run on the Linux kernel using real-time policies like SCHED_DEADLINE, making them suitable for sophisticated embedded and industrial environments as well.
Developing for real-time involves choosing the right RTOS and designing applications with explicit deadlines, often measured in milliseconds. Techniques such as Earliest Deadline First (EDF) and Rate Monotonic Scheduling (RMS) are commonly used for scheduling. Real-time virtualization solutions are also employed when combining deterministic real-time performance with general-purpose operating systems on the same hardware.








