  SMG$CREATE_SUBPROCESS and SMG$EXECUTE_COMMAND? 
 The Question is:
 
Can I find somewhere more information (an example)
on how to use the IPC communication mecanism
created between a virtual display (SMG) and its subprocess?
There's a little bit information in the SMG$CREATE_SUBPROCESS
and SMG$EXECUTE_COMMAND, but it's not enough to
figure out, how the mailboxing mecanism is implemented!
 
Thank you
 
 
 The Answer is:
 
  The protocol involves issuing smg$execute_command calls to pass in the
  command to be executed, and having the AST routine that was specified by
  smg$create_subprocess triggered for the output.
 
  Issue the smg$create_subprocess call, then pass in commands via calls to
  smg$execute_command.  Output and status returns via AST calls.  The key
  flag when passing in image data -- rather than new commands -- is the
  SMG$M_DATA_FOLLOWS flag.
 
  There is a BASIC example of using the call included directly in the SMG
  manual, in the section describing the sys$create_subprocess call.
  Additional examples are likely available via DSN and/or via the customer
  support center.
 
