🚀 go-pugleaf

On Fri, 8 Dec 89 13:26:20 TUR Bahri Bora BALI AG said:
>Hello.. I've seen a statement part like X'608'(0,0) in an assembler program.
>R0 has been used for NUCON. (USING  NUCON,R0) What information is contained
>starting from address X'608' in CMS nucleus. I didn't find any information
>which makes sense. Any ideas ? Thank you..
>
>-Bora
Bora -

In general, anybody who codes  X'608'(0,0) should be shot by a firing squad
at dawn.

The problem is that in general, fixed offsets aren't.  Just a few weeks
ago, we had to fix a problem here for the HPO/5 version of CMS, where the
'USERSECT' area had moved in memory compared to HPO/4.2, and we had code that
only knew about it as a fixed address.

In VM/XA SP2, x'608' in NUCON is SYSNAME - the name of the system you
gave on the IPL command - if you said 'IPL CMS', it has a CL8'CMS' in it.
If you said 'IPL CMSTEST', it has CL8'CMSTEST'.  A handy value to have
around...  Of course, SYSNAME could be at other offsets for other releases.

The *proper* thing to do is of course reference it using the handy labels
in the NUCON macro.  If nothing else, it makes for easier code:

         NI    x'19'(0),x'FC'      turn off run bit

versus

         NI    EXTOPSW+1,X'FF'-X'02' turn off run bit.

Plus, if you use the mapping macros, you can (a) look at the comments that
they provide on what the field is and (b) when a new release of CMS comes out,
you have at least a snowball's chance you-know-where of having it still work
after you re-assemble against the new maclibs...

                                   Valdis Kletnieks