Hello Srivathsa,

I don't have detailed differences but I can offer some generalities.

MPE 4.0 is the last release of MPE/iX that does not support POSIX.  I don't
think 4.0 is supported any longer.

MPE 4.5 is the POSIX "developers" release.  It was our first support
of the POSIX.1 APIs and the POSIX.2 shell.  This was a partial implementation
targetted at UNIX and MPE developers.  It is no longer supported.

MPE 5.0  has better support for the POSIX APIs and better integration of
MPE operations and POSIX operations.

I recommend that you read the associated Communicator articles linked to via
our MPE webserver named jazz.  See:
   http://jazz.external.hp.com

regards,
Jeff Vance, CSY

--