An RTOS differs from a common OS in that it allows direct access to the microprocessor and peripherals, helping to meet deadlines. An RTOS provides mechanisms for multitasking like scheduling, context switching, and IPC. It uses techniques like priority-based preemptive scheduling and memory management with separate stacks and heaps for tasks. Common RTOS services include timing functions, synchronization, resource protection and communication between processes.

1. RTOS Concepts