The Apollo Guidance Computer

Home Index by Year Index by Author Index by Doc. No. Glossary Chronology LGC Simulator


For 15 manned missions (and 4 unmanned ones) the Apollo Guidance Computer (AGC(1)) provided in-spacecraft guidance, navigation and control facilities to both the Command and Service module (CSM) and Lunar Module (LM or LEM).  Its development and updating at the MIT Instrumentation Laboratory was a major undertaking lasting for all of the 1960's and involving many people at all levels.

As is often the way with such intense projects, all involved are focussed on the next deadline or deliverable (the most obvious being the end of the decade for the first landing).  Thus little thought is (understandably) given to the needs of historians in terms of documents.  Much of the paperwork generated during these years has simply vanished.  Much must have been discarded soon after it was produced (for example, the software ran to nearly 1800 pages of line-listings and boxes of these must have been happily jettisoned once a particular mission had been flown).  All the printed reports and manuals were originally filed in the MIT library.  However much of this also has been tidied into oblivion over the years.  With such a momentous project, many of those involved must also have taken mementos of their labours.  Some of these have trickled back to MIT over the intervening thirty years or so, but much must have been lost as their owners gracefully aged.  This same aging has also led to variable degrees of accuracy of recollection on the part of the original participants.  Thus some recently printed sources, whilst valuable in capturing the spirit of the age, contain unwitting technical errors. 

As the years take their toll, those interested in the technologies involved in the development of the AGC must increasingly rely on the limited documents publicly available.  The most important resource to students of the AGC is the MIT History of Recent Science and Technology (HRST) project which in part is targeting the AGC.  What must have been tireless enthusiasm has resulted in around 80 documents of various types being available in scanned-in form.  However, these documents range over a period of 46 years (1954 to 2000) and since there is no convenient index to them it is somewhat difficult for new researchers to find their way into the material.  In particular many documents supersede earlier documents and incorrect conclusions might be drawn by referring to a document without knowing its Apollo programme context.


This site has a number of aims - some of them long-term:

  1. to provide an AGC assembler and simulator capable of assembling and running the original programs (the assembler and simulator aren't too hard, however the few remaining programs are only available as assembly listings - hence a lot of typing will be required)
  2. to provide an authoritative introduction to the Apollo Guidance Computer for computer scientists and historical researchers
  3. to provide easy-to-use indexes and abstracts for the MIT History of Recent Science and Technology file of scanned documents relating to the AGC
  4. to provide a detailed technical look at the AGC as flown particularly at the software level

1) Apollo Guidance Computer (AGC) includes the occasionally encountered specific terms CGC (Command-module Guidance Computer) and LGC (Lunar-module Guidance Computer) plus all earlier versions leading to the flown AGC

  ( visitors to this page since 18 Feb 2004)

Page maintained by Julian Webb 2004 University of the West of England, Bristol