------------------------------<snip>------------------------------
The 360 instruction set is wholly contained in the z/Series instruction
set and many system constructs were extended in such a way as to make
them backward compatible.
----------------------------<unsnip>-----------------------------
Not strictly true; SIO/HIO/TIO are no more than fond memories today.
There might be a very few others, but these are the ones I remember most.
------------------------------<snip>--------------------------------------------
Some system functions (like the ISAM access method) no longer exist, and
some things you could get away with in the early days (think OS/360)
were closed as security or reliability loopholes in MVS.
----------------------------<unsnip>----------------------------------------
ISAM is no great loss, but I don't know if the ISAM Compatability
Interface is still available to convert ISAM calls to the equivalent
VSAM mechanisms.
---------------------------------<snip>------------------------------------
Most macros are backward compatible as well, although some may require
re-assembling to work correctly today (but offhand, I can't think of any
examples).
----------------------------------<unsnip>--------------------------------
AFAIK, only some macros that require a few specialized systems services
are incompatable. Just about everything that application are expected to
use are pretty much unchanged, or at least compatible.
-----------------------------------<snip>--------------------------------
Some ancient programs like DEBE and Ditto still run on a z/Series
machine under z/OS, although they may have been reworked to do so. I
don't still have any of my ancient programs to try out myself.
-------------------------------------<unsnip>-----------------------------
Any old stand-alone programs that do ANY I/O will need to be reworked,
because of the loss of SIO/TIO/HIO instructions and changes in the
overall architecture in this area. Also programs that expect to use
certain areas of the first 2K of storage.
In my experience, very few surviving OS/360 application programs will
fail on z/10 machines. Providing you have access to the correct run-time
libraries.
Rick
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