The Apollo spacecraft used for lunar missions in the late 1960’s and early 1970’s was really two different spacecraft, the Command Module (CM) and the Lunar Module (LM). The CM was used to get the three astronauts to the moon, and back again. The LM was used to land two of the astronauts on the moon while the third astronaut remained in the CM, in orbit around the moon.
The Virtual AGC project provides a virtual machine which simulates the AGC, the DSKY, and some other portions of the guidance system. In other words, if the virtual machine—which we call yaAGC—is given the same software which was originally run by the real AGCs, and is fed the same input signals encountered by the real AGCs during Apollo missions, then it will responds in the same way as the real AGCs did. The Virtual AGC software is free of charge, can be obtained for Windows, Mac OS X, Linux, or as open source software source code so that it can be studied or modified.