An event flag is a process synchronization primitive in the OpenVMS operating system. It has two possible states, set or cleared. The following basic primitive operations are provided: * Set event flag ($SETEF) * Clear event flag ($CLREF) * Wait for event flag ($WAITFR)--if the flag was clear, this would make the process wait until it was set. If the flag was already set, this would immediately return, leaving the flag set. Additional synchronization operations are: Compare semaphore.