BROADCAST user "message"
or BROADCAST/CLASS=USER1 user "message"
Sends the specified message to all terminals belonging to user.
If message is missing, it is read from sys$input line by line.
User may be a (comma separated) list of users.
/CLASS=broadcastclass may be one of the classes valid for SET BROADCAST,
except ALL or NONE. Default is GENERAL.
To make the command available to DCL, either
$ broadcast :== $location:broadcast ,or
put broadcast.exe into DCL$PATH, and use command broadcast.