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README.1ST
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README.1ST
This text contains important information regarding the latest
version of DPN together with any last minute additions to the
user manual.
1. VERSION 2.0
----------------
Version 2.0 of DPN as supplied on your distribution disk
contains major revisions over previous versions.
Most importantly of all, DPN has undergone a re-think and
TOTAL re-write. This has eliminated some bugs that persisted
in version 1.x, and means that DPN is now very much faster in
operation. Unfortunately, client programs written under
version 1.x of DPN will no longer run under version 2.0 as the
two systems are completely incompatible. As DPN is still an
infant product it is hoped that this will not cause users too
much inconvenience. The documentation which accompanies
version 2.0 fully describes the new system and porting version
1.x client programs to version 2.0 is very straightforward and
will certainly offer improved performance.
Sub-programs which perform the work of a task and which run on
remote hosts should not require any revision as they do not
use any of the DPN libraries or functions. The exception to
this is the sub-program which also spools tasks for remote
execution. These do include DPN code and will need to be
revised and re-compiled using the version 2.0 libraries
supplied.
Please note that while version 1.x will still be supported for
registered users, no further revisions of this old system will
be undertaken, and as a few bugs have since come to light,
existing users of earlier versions of DPN are strongly
recommended to upgrade at the earliest opportunity.
Registered users will automatically be receiving upgrades free
of charge.
1.1 Main Changes
-----------------
The most significant change is that C++ support is now
included. Versions of the DPN libraries are now included for
C++ and object Pascal. There are a few minor differences
between the two due to the languages themselves, but both
libraries are fully described in the accompanying
documentation. All the C++ memory models are supported.
The concept of naming remote host machines and spooling tasks
to hosts by name has been removed. This was found to
introduce an unnecessary degree of complexity for minimal
return. The new system means that hosts are completely
anonymous and this makes programming and network maintenance
much simpler. Remote task turn-around time has also been
improved by this change. Host anonymity means that the
environment variable NODENAME which was required by version
1.x is no longer required and can be removed from host start-
up files.
The system log facility has also been deleted. In practical
use this was found to have very few benefits, unless you are
keen to use up disk space! Even during development of DPN it
was rarely used and merely slowed the system down.
The process of sending the task to a host has now been
included within the constructor method of the Task object.
Version 1.x Pascal users will recall that the tasks were
separately initialised with parameters and then spooled. This
new system reduces the amount of code required in client
programs, and makes use of the functions less open to error.
The Task object now includes an independent error code,
instead of a global DPN error variable. This is accessible
through a Task member function and means that the error code
available truly reflects the status of that particular task
and will be unaffected by other DPN operations.
The Task object now has in-built facilities for returning the
exit code returned by a host sub-program on it's termination.
This is retrieved automatically when the Finished method
returns true.
Global DPN functions have been added to allow the programmer
easy access to the NETTIME and NETDRIVE environment variables.
Existing global functions have been re-written to comply with
version 2.0 operation.
2.0 Utility Programs
---------------------
Your distribution disk contains a number of utility programs
which do not form part of the DPN system but may be used with
it to perform certain tasks.
2.1 NOTHING.EXE
----------------
This short program does exactly that, nothing! Running it
from the DOS prompt will return you straight back. This was
included as a sample program to use in setting up the DPN
system. Client programs may spool this program to the job
queue as a sub-program, and if a monitor is connected to the
remote processor, the execution of the task can be monitored.