The Apollo Guidance Computer (AGC) was the first recognizably modern embedded system, used in real-time by astronaut pilots to collect and provide flight information, and to automatically control all of the navigational functions of the Apollo spacecraft. It was developed in the early 1960s for the Apollo program by the MIT Instrumentation Laboratory.
It was the principle for all Apollo Missions and there were two of these on-board. One to control the Command Module, a space craft that would take the three astronauts to the moon and back to Earth. The other controlled the Lunar Module that was used to land two of the astronauts on the Lunar Surface.
The software that was released is called the Virtual AGC and is an emulator for the Original AGC and was made by the developers after studying the hard-copy scanned images of the original source code from both the Spaceship modules.The Virtual AGC has been released under both Binary and Source code form and is available for all the three commonly used platforms.
Virtual AGC can be obtained from http://www.ibiblio.org/apollo/ where the developers have provided with HOWTOs, guides and FAQs for using it.