[TUHS] What was your "Aha, Unix!" moment?

[Doug McIlroy]

Apropos of Steve Johnson's evocative description of JCL and other
pre-Unix OS interfaces, doing legwork for Multics I ran the following
experiment on a lot of then-current time-sharing systems.

As a model of creating and installing a new compiler, I used a very
short Fortran program that simply copied its input to its output,
stopping after finding END in column 7 of the input. The drill was
	compile the program
	run it, using its own source as input
	compile the freshly made output file
This failed on every system I tried it on, though local
experts could intervene with magic to overcome the
gratuitous file-type distinctions that typically 
got in the way. Dartmouth's DTSS came closest, but
inexplicably, even to the gurus, it had a special 
prohibition against a program reading the source
from which it was compiled.

Incidentally, my favorite manifestation of JCL-like mumbo jumbo
was the ironically named FUTIL control card in GECOS.

Doug