Pcomm (actually, VAX protection)

[Jon Corbet]

A minor quibble:

jmb at patton.SGI.COM (Jim Barton):
>  Some primitive architectures (such as the VAX)
>allow you to de-reference 0 and get 0 back - most modern systems disallow this. 
The VAX, like any reasonable virtual-memory machine, has individual page
protection.  VMS sets page zero (which, obviously, contains the address zero)
to be no-read-no-write, thus causing an exception when a zero pointer is
dereferenced.  BSD, as I recall, will do this only if you pass a special
flag to ld.