The authors survey the state-of-the-art in real-time operating systems (RTOSs) from the system synthesis point of view. RTOSs have a very long research history which provides important theoretical results and useful industrial implementations. Convergence of applications, technology, and market trends of embedded systems implies a strong need for new generation of RTOS. Therefore, new system synthesis problem areas, notably hardware/software co-design and synthesis for systems-on-silicon (SOS), are opening up new avenues for RTOS research and development. The paper starts with a survey of classical academic and industrial RTOS work and continues with a survey of recent results related to co-design and design systems-on-silicon. They conclude by outlining future directions for the SOS RTOS Author(s) Yanbing Li Dept. of Electr. Eng., Princeton Univ., NJ, USA Potkonjak, M. ; Wolf, W.