I wanted to write down a few remembrances of JMC: He was colloquially known at SAIL as just "J M C", not John, not Professor McCarthy. He was at the lab daily and often at night -- his office was in the front of the building. When I first started "flirting" with the AI lab during high school, I was afraid he'd toss me to the curb if he would discover that I was just a high school student. But I believe he just didn't care. In fact, the lab machine would allow you to create an account just by logging in.
When I worked for the computer music project, I saw him often. My most salient memory is when he came into my office (I shared with Bill Gosper and Mike Farmwald) to ask about the radical left poster next to my desk. He wanted to know if I believed whatever was on the poster. I didn't, but I liked the sort of visual style. He said, "OK, I just wanted to know" and walked away. (For those who don't know, JMC took a decidedly right wing turn during the 1970s. Given the background of his parents, that's a remarkable trend).
I can't really separate the contributions of JMC and Les Earnest towards the ultra cool working environment of the AI Lab. To this day, I don't know whether it was the fact that I was fresh out of college or whether it was just a cool place that made the AI lab so special. One must acknowledge that JMC approved of the computer music people coming in over night to use the machine. Without this approval, would computer music have progressed so fast? John Chowning and company depended on this largesse.
McCarthy's contributions to computer science are well known and don't bear repeating. But I'd like to mention two of them in particular: The first is timesharing. As I understand it, the reason the PDP-1 could timeshare was that the drum (not disk, drum) had the ability to read and write simultaneously. So, when the current running user was swapped out, the entire memory was written to the disk while the next user was read in! Second, Markoff's obituary in the Times points out that McCarthy invented Garbage Collection of memory. What a concept!
JMC clearly had a potent vision of that was possible with computers: he sponsored research in AI but also sponsored the system research that would propagate from the lab. So, while we remember McCarthy and Lisp, we should also remember his creation of the Stanford AI Lab and all that came forth from that place.