> On 2019-11-25, at 09:37:13, John McKown wrote: > > On Mon, Nov 25, 2019 at 10:04 AM Gary Weinhold wrote: >> ... >> There's more to it than that, of course. But the developers of z/OS >> decided that 31-bit programs should be minimally impacted by 64-bit >> addressability. >> > I'd much perfer an S0C4-38 than having a 31 bit address from a non-64 bit > application with the "end of list" bit 32 set accessing some address which > might actually be valid but not the correct page/data. > I believe the greater accommodation was the hardware architecture's expanding from 24-bit addressing to only 31 rather than 32 because software so pervasively uses the sign bit for a flag.
-- gil
