Description

   Your symbiont calls SMB$READ_MESSAGE to read a message that the
   job controller has sent to the symbiont.

   Each message from the job controller consists of a code
   identifying the function the symbiont is to perform and a number
   of message items. There are seven codes. Message items are pieces
   of information that the symbiont needs to carry out the requested
   function.

   For example, when you enter the DCL command PRINT, the job
   controller sends a message containing a START_TASK code and
   a message item containing the specification of the file to be
   printed.

   SMB$READ_MESSAGE writes the code into a longword (specified by
   the request argument) and writes the accompanying message items,
   if any, into a buffer (specified by the buffer argument).

   See the description of the SMB$READ_MESSAGE_ITEM routine for
   information about processing the individual message items.