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.

-Steve


> On 26 Nov 2015, at 17:48, Bakul Shah <bakul@bitblocks.com> wrote:
> 
> Good points! Though 0 was a valid address on pdp11, right?