Which makes me curious... Does anyone here happen to
know when #if was introduced in C?
From what I can gather from studying the TUHS archives,
the earliest
cpp that supports #if is in PWB:
http://minnie.tuhs.org/cgi-bin/utree.pl?file=PWB1/sys/c/c/cpp.c
Before that, the pre-processor resides within the cc.c command and #if
is not supported:
http://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/source/s1/cc.c