The Apollo Guidance Computer Architecture and Operation

More than any other system in the Apollo spacecraft, the Apollo Guidance Computer drove the capabilities of the lunar missions. In the 1960's, most computers filled an entire room yet the spacecraft's computer was required to be compact and require little power. When compared to modern systems, the AGC's design limitations and lack of speed presented formidable challenges.
Yet, hardware and software engineers overcame these difficulties, and their creation was able to guide a new and complex spacecraft and its precious human cargo away from the safety of Earth and towards a new world. Although people today find it difficult to accept that it was possible to control a spacecraft using such a 'primitive' computer, it nevertheless had capabilities that are advanced even by today's standards.