The operating system supports
a virtual device, called a mailbox, that is used for communication
between processes. Mailboxes provide a controlled, synchronized
method for processes to exchange data. Although mailboxes transfer
information much like other I/O devices, they are not hardware devices.
Rather, mailboxes are a software-implemented way to perform read
and write operations between processes.
The OpenVMS Programming Concepts and the HP OpenVMS System Services Reference Manual contain additional information
about using mailboxes.
HP OpenVMS I/O User's Reference Manual
