Source : Free On-Line Dictionary of Computing

Real-Time Operating System
     
         (RTOS) Any {operating system} where
        interrupts are guaranteed to be handled within a certain
        specified maximum time, thereby making it suitable for control
        of hardware in {embedded systems} and other time-critical
        applications.  RTOS is not a specific product but a class of
        operating systems.
     
        [Other criteria?]
     
        (1998-02-27)