On Nov 26, 2015, at 6:14 PM, Steve Simon <steve@quintile.net> wrote:I don't know about the PDP but the VAX allowed access to address zero.Even more insidious, it allowed you to dereference a null pointer and guaranteed it would contain a zero, which resulted in many tiresome portability issues - I used Interdatas at the time, which faulted on a read at address zero.-SteveGood points! Though 0 was a valid address on pdp11, right?