Real-time systems must accomplish executive and application tasks within specified timing constraints. In distributed real time systems. the mechanisms that ensure fair access To shared resources, achieve consistent deadlines, meet timing or precedence constraints, and avoid deadlocks all utilize the notion of a common system-wide time base. A synchronization primitive is essential in meeting the demands of real time critical computing. This paper provides a tutorial on the terminology, issues, and techniques essential to synchronization in real time systems. © 1994 IEEE