Real-Time Operating Systems

An RTOS runs multiple tasks with priorities and guaranteed timing on a microcontroller.

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An RTOS like FreeRTOS or Zephyr provides:

tasks (threads) with priorities and a preemptive scheduler,
queues for passing data between tasks,
semaphores and mutexes for synchronisation,
software timers.

void blink_task(void *arg) {
    for (;;) {
        gpio_toggle(LED);
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}
xTaskCreate(blink_task, "blink", 128, NULL, 1, NULL);
vTaskStartScheduler();

"Real-time" means deterministic — a high-priority task always runs within a known time — not necessarily "fast". Watch for priority inversion, solved by priority-inheritance mutexes.

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