Mark writes:
> As of 6.5, the C compiler has been enhanced to use long long (and
> unsigned long long). As such, there is some new millicode that has
> been added in support of that.

On the other hand, there's no such thing as an external millicode call, so
any new millicode would get bound into the program at link time, and would
therefore be part of the program file.  Compiling on 6.5 and then trying to
LINK on an earlier version might be a problem, but (at least conceptually) I
don't see a backwards compatibility issue arising just from the long long
data type and it's associated millicode.

G.