The Invoke $GETMSG System Service to Get Message Text routine
    calls the system service $GETMSG and returns a message string
    into destination-string using the semantics of the caller's
    string.

    Format

      LIB$SYS_GETMSG  message-id [,message-length]

                      ,destination-string [,flags]

                      [,unsigned-resultant-array]