When I modify Unix v5 I have strict rules which I will not deviate from. First of all I
haven't made any modifications to the C compiler. So any new code created for v5 must
compile with the existing cc program. Also no modifications have been made to the existing
device driver code or kernel (beyond simply compiling it). If I was to try to run a newer
compiler or make alterations to the kernel it wouldn't really be version 5 any more. On
the other hand, I feel writing new programs or backporting programs to v5 is fine, as long
as the original disk image is kept intact. After all, if I wanted to use a newer C
compiler I could simply use v6 or v7 or any of the newer versions.