In fact, though, the guidance computer had performed as it was supposed to perform. As the craft approached the lunar surface, Armstrong used his controller to instruct the computer to change the landing site to a smoother section of terrain, and the guidance computer kept humming right along until the contact light went on.
An unsung hero of the decision not to abort the landing is Richard Koos, a NASA simulation supervisor who, on the afternoon of July 5, 11 days before the launch of Apollo 11, put the team of controllers including Bales, Garman, and capcom astronaut Charlie Duke, through a simulation that intentionally triggered a alarm.
The astronauts involved in the simulation were Dave Scott and Jim Irwin, the backup crew for Apollo 12 and the prime crew for Apollo Only weeks before, the mission controllers had messed up in a simulation when they called an abort and it turned out that it wasn't necessary, according to NASA.
After the bad sim, Bales asked his even younger deputy, Jack Garman , to draw up a "cheat sheet" list of abort codes and what they meant. Bales tucked his copy under a sheet of glass; Garman had his right in front of him during landing.
So, it was Garman, sitting in a back room, who found the list more quickly and could tell Bales that a alarm was not a concern. The advisory meant that the computer was slightly overloaded, but did not indicate a risk of the spacecraft crashing. Garman told Bales, who told the flight director, and within moments the concerned Armstrong got his answer and proceeded with the landing process.
After a few more similar error codes, Eagle touched down safely on the lunar surface. There were many factors behind Eagle's successful landing, which took place 50 years ago this July, and among them Bales points to the team feeling in Houston's mission control.
Flight director Gene Kranz had told his controllers, "When we walk out of this room, whatever happens, we're walking out as a team," Bales recalled Kranz said. Stepping forward 4 more positions arrives at opcode 99 , halting the program. Once you have a working computer, the first step is to restore the gravity assist program your puzzle input to the " program alarm" state it had just before the last computer caught fire. To do this, before running the program , replace position 1 with the value 12 and replace position 2 with the value 2.
What value is left at position 0 after the program halts? Our sponsors help make Advent of Code possible:. Ximedes - Help us write elegant, secure, and performant software that enables payments worldwide. We're hiring in the Netherlands and Serbia! For the sake of simplicity, each task a task in this case would be a single mission event like the lunar landing was broken down into parts. These parts or programs were manageable modules that could be run individually while rendering the whole system more reliable.
The Apollo Guidance Computer was a single processor computer, computer. So how could it run multiple programs — the parts that make up a whole mission event — simultaneously? Not really. But between relatively fast processing speed and relatively slow human perception it was simultaneous enough to run the mission smoothly.
The programs were also scheduled and run based on priority with measures in place to interrupt any program should something vital come up. This contained all the information to execute a given program. The seven remaining words were left for temporary variables or extra storage … whatever they might be.
So in short: twelve words in the Core Set, five words of memory to execute a program, and the seven MPACs deal with the extra information as needed. Scheduling a program falls to the Executive. This scans the core set to see if there is any available space for the program to execute, and if so where that space is. It then schedules and runs the program. There would always be space available for the next program, rules in place to interrupt a program if something needed to be run immediately, or space to schedule the program after whatever was currently being run through the computer.
But when Apollo 11 was descending towards the lunar surface, the computer ran out of Core Sets.
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