At the time, everything seemed so routine -- if landing on the Moon can be considered routine. Only afterward have we found out that the 1201 and 1202 alarms which were quickly overridden were potentially mission ending computer errors.

I had also been under the impression that the 60 seconds and 30 seconds were not the time to landing but the time to a fuel level abort.

I recall being in a high state of suspense while watching (the in real time simulation of) the moon landing on TV way back in 1969.
Simulated was the moon's ground coming up beneath an animated flame.
I do appreciate someone finally telling me about Margaret Hamilton 45 years later.
Thanks, nickursis.

We are currently watching the Moon Machine series. That episode is particularly interesting

we have argued this before and I think we have different understandings of what switches do. I'm not going to hijack the post for that discussion. I do agree with Hamilton's smile reflecting a sense of life I so appreciate.

I heard that. I heard they struggled to find a landing zone with a flat enough grade because if the grade were too steep they would not be able to take off again. They had something like 60 seconds of reserve fuel that was supposed to be for emergencies, but they used some of it b/c paraphrasing Buzz Aldrin, you don't have the right stuff if you come all this way and abort the landing to maintain a reserve.

While all this was going on, they had two false alarms.

I hadn't heard of Ms. Hamilton or how she wrote a custom RTOS of sorts that helped save the landing. Very cool.

I remember Astronaut Armstrong saying he had to steer clear of the original LZ, which was a football-field-sized crater strewn with automobile-sized boulders.

My understanding is the roped memory acted as a ROM (Read Only memory) since by making it physical instead of any of the (then new) DRAM that was available to DARPA, they could avoid any possibility of corruption. There was a lot of questions then in regards to cosmic ray damage to electronics. A lot of the boot systems used for mainframes had it just like todays BIOs. I had a similar boot system on 2 UYK-7s on a Trident SSBN back in the 80s and early 90s.

Software does not "wire" a computer, it is used to control it. The "wiring" does not change while a program is running. There have been many ways to represent binary states in computers; the Apollo guidance computer (which had less power than the one on your desk, lap, or hand!) used integrated transistor circuits with a combination of transformer coiled ("roped") and magnetic core memory. The essence of software is that it is a means to logically control the states of a machine regardless of how those states are represented in hardware. That includes the original punch card programming for mechanical gears and levers in Babbage's original computer design in the 19th century.

But Hamilton's smile was typical of the sense of intellectual accomplishment in logically programming computers in a new field. (It's good thing she was short, if she were taller they wouldn't have had time to write more code for a higher pile!)

great article! Her smile is infectious! I really enjoyed that. "Roped memory" is an excellent reminder to those (including software engineers) that software is a way of "wiring" the hardware.