
XBCAST - Purpose and explanation
--------------------------------

When Windows starts up and shuts down, it sends, via interrupts, messages to
applications saying that it has started or quit.  If you have Smartdrv loaded
on your machine, it will listen for these messages, and alter its cache size
accordingly, from it's normal DOS size to its special Windows size.

The program XBCAST that can sometimes be found in the CDD.BAT file, and which
was shipped with 3006 and 3007 simulates sending this message.  The line
XBCAST + will send a startup message. Smartdrv will see this message and shrink
to it's Windows cache, giving more memory to CDD and your application. In
reverse, the call to XBCAST - will send a shutdown message, allowing Smartdrv
to return to it's normal size.

(Of course, one side-effect of this is that if you run your application from the
CDD environment, it will run slower than under normal DOS, because the Smartdrv
cache is smaller.)

However, problems may occur if you run CDD under Windows, depending on how
clever Smartdrv is.  When Windows starts, it would send its startup message
and Smartdrv would shrink. CDD would then start, sending it's message.
Smartdrv can't shrink any more, because it has already done so.

The problem occurs when you quit CDD.  This will send a shutdown message to
Smartdrv. Now, either Smartdrv sees a call to a shutdown message, and grows
back in size, thus having a DOS size cache under Windows. Or it will be
clever, and realise that it has had 2 startup messages but only 1 shutdown
message, and so will stay the same (small) size until you quit Windows.

Now, this is where QBCAST comes in. You can use this instead of XBCAST, the
only difference being that it will detect whether it is under Windows. If it
is, then it won't send a message, because obviously it won't need to. Also,
QBCAST will not send the startup/messages if the CDD batch file is running
under Windows NT.

To use QBCAST, run it as you would XBCAST, with the + and - switches. You can
also specifiy ? or ! to get the version number. When it runs and can't send
the message, it will display a message to the screen. Obviously this may be a
problem for some users, who should redirect the output of the program by >NUL.

Please remember QBCAST is an unsupported program, not offically endorsed by
Clarion Software.

If you have any queries, please contact Paul Attryde at Clarion Tech Support:

Voice: +44 (0)582 763999
Fax:   +44 (0)582 768222
BBS:   +44 (0)582 769666
Mail:  Clare House
       Thompsons Close
       Harpenden
       Hertfordshire
       AL5 4ES
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