The historic computer software code that took Apollo 11 to the moon has been open-sourced and is available for anyone to read, download, and tinker with. NASA’s Chris Garry made the code available on GitHub as public domain. The published resource is basically in two large codebases, one set of code for the Command Module (Comanche055) and another for the Lunar Module (Luminary099). These modules both had their own Apollo 11 guidance computers (AGC) upon which to run the code, and were instrumental to the success of the remarkable mission – the first human Moon landing in history.

On the GitHub repo, Garry indicates that this momentous code was digitized by the folks at Virtual AGC (Virtual Apollo Guidance Computer) and the MIT Museum. That means the hard copy of the code held at the MIT Museum has been scanned and proofread for digital distribution. In this particular case, we have reams of machine code now in the public domain, easily accessible online.

To take a closer look at some of the example code, we dived into the Commanche055 directory, and the first interesting file that caught our eye was ALARM_AND_ABORT.agc. After a boilerplate introduction to the code at the top of the file, the purpose of the code is revealed – something which is quite obvious from the file name in this instance. Moreover, comments within the code reveal that the code logs alarm conditions, turns on a warning light if applicable, and handles various abort-level and non-abortive alarms.

Another interesting code example, shared on social media (embedded above), highlights the crucial 30 lines of assembly for calculating Apollo 11's navigation trajectories.

If you want to go beyond nosing around the historic codebase, it is possible to compile the code now shared into the public domain using the Virtual AGC tool (GitHub link). The Virtual AGC software has been designed to work in Linux, in Windows XP/Vista/7, and in Mac OS X 10.3 or later, and some versions of FreeBSD. This repo is also a good place to learn about the AGCs carried on both the Command Module and the Lunar Module.

The specs of the AGC pale in comparison to even the most rudimentary computers today. For example, an AGC had just 3,840 bytes of RAM and 69,120 bytes of storage. It could run at a maximum of about 85,000 instructions per second. Nevertheless, it was comparable in size to a desktop gaming tower PC of today at 24.250 x 12.433 x 5.974 inches (61.595 x 31.580 x 15.174cm), and weighed 70.1 pounds (31.8kg). It also needed two DSKY controller units at 17.8 pounds (8.1kg) each in the Command Module, and one DSKY in the Lunar Module.

Over half a century before Artemis II

It is fascinating to see this Apollo 11 code from nearly 60 years ago shared in the context of the ongoing Artemis II lunar mission. Today, we aren’t marveling at the lean and mean machine code that NASA is using to get humans to and from the Moon. Rather, Microsoft Outlook email bugs and a malfunctioning toilet on the Orion spacecraft may have taken the shine off the momentous achievement this latest mission represents.

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Mark Tyson is a news editor at Tom's Hardware. He enjoys covering the full breadth of PC tech; from business and semiconductor design to products approaching the edge of reason.