What is an RTOS and how does it differ from a general-purpose OS?

An RTOS (Real-Time Operating System) is an operating system designed to process data and events within guaranteed time constraints (deadlines). Key differences from general-purpose OS: Deterministic behavior with bounded response times. Priority-based preemptive scheduling ensures critical tasks run first. Minimal latency for interrupt handling and context switching. Small memory footprint and fast boot times. No virtual memory or memory protection in many cases for speed. Examples include FreeRTOS, VxWorks, QNX, Zephyr, and RTEMS. RTOS is used in automotive, aerospace, medical, and industrial applications where missing deadlines can be catastrophic.