Event flag

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:

Additional synchronization operations are:

Event flags can be either local (per-process) or common (accessible by more than one process). Each process has its own set of 64 local flags, numbered 0-63. It is also possible to associate the process with up to 2 sets of common event flags. These come in sets of 32 each, and the process can assign them numbers 64-95 or 96-127. They come into existence when the first process associates with them, and disappear when the last process removes its association.