In article by Fred N. van Kempen: Was it this story (from http://cm.bell-labs.com/cm/cs/who/dmr/odd.html) Back around 1970-71, Unix on the PDP-11/20 ran on hardware that not only did not support virtual memory, but didn't support any kind of hardware memory mapping or protection, for example against writing over the kernel. This was a pain, because we were using the machine for multiple users. When anyone was working on a program, it was considered a courtesy to yell "A.OUT?" before trying it, to warn others to save whatever they were editing. [A substory: at some point several were sitting around working away. Bob Morris asked, almost conversationally, "what are the arguments to ld?" Someone told him. We continued typing for the next minute, as a thought began to percolate, not quite to the top of the brain - in other words, not quite fast enough. The terminal stopped echoing before anyone could stop and say "Hold on Bob, what is it you're trying to do?"] Warren