What are the key components of an RTOS?

A preemptive scheduler, communication mechanisms (semaphores, queues), critical-region mechanisms (mutexes, locks), timing services, power management, memory management, peripheral drivers, protocol stacks and device management.

The scheduler is the core, and the rest either feed it information or let tasks cooperate safely:

1. Scheduler — preemptive; guarantees the highest-priority ready thread is running.
2. Communication mechanisms — semaphores, message queues and queues, so tasks can signal each other and pass data.
3. Critical-region mechanisms — mutexes, gates and locks, so only one task at a time touches a shared resource.
4. Timing services — clocks and timers for delays, timeouts and periodic work.
5. Power management — usually part of the RTOS, because it knows the state of every task and can put the chip to sleep when nothing is ready.
6. Memory management — variable-size and fixed-size heaps; fixed-size pools avoid fragmentation and have predictable allocation time.
7. Drivers — peripheral drivers for UART, SPI, I2C and so on.
8. Protocols — protocol stacks such as BLE and Wi-Fi.
9. Device management — exception handling, boot and similar system services.

Power management belongs to the RTOS for a concrete reason: when every task is blocked, the scheduler knows the next time anything needs to happen, and can sleep until then. That is how an RTOS device reaches years of battery life.

Go deeper:

• DigiKey — Introduction to RTOS Part 2: Getting Started with FreeRTOS — the FreeRTOS kernel and its first task on an ESP32.