For the past few years, we’ve had a number of 50-year milestones for the various manned lunar flights. Apollo 8 circled the moon in December 1968, and the following year Apollo 11 made the first manned lunar landing on July 20, 1969. Besides Apollo 11, there were five other lunar landings, ending with Apollo 17. (Apollo 13 was scheduled to land in April 1970, but famously did not.)

In honor of those anniversaries, I thought I’d share one of the best videos I’ve ever seen. With that opening paragraph, you may think it’s a documentary about the Apollo program. It does, in fact, have to do with Apollo, but a very specific part. I’m talking about the Apollo Guidance Computer.

The Apollo Guidance Computer (AGC) was a miniaturized (by 1960s standards) computer that oversaw much of the operation of both the command and lunar modules. It’s an impressive piece of technology, despite advances in the year since. Your average smartphone is “far more powerful” but power isn’t the point. The AGC was suited to the task of landing on the moon, and it operated well.

Rather than go into a long rant about the features of the AGC, that’s what this video is for. It’s from a series of talks about classic computer architecture, and to me, this one is the most impressive. It’s fairly technical but quite informative.

There’s a really funny moment in this video that’s a bit inside-baseball for programmers. You’ll know it when you hear the audience laughing. It definitely got me the first time I heard it.