Source Code

These source-code files are part of a reconstructed copy of Comanche 51, the initial release (though not the final mission release) of the Apollo 11 Command Module (CM) Apollo Guidance Computer (AGC) software. The flown, final release was Comanche 55. The reconstruction is believed to be exactly accurate, but in the absence of an actual Apollo-era listing of Comanche 51, some explanation of the reconstruction process is needed to insure confidence in that accuracy. The starting point was the source code of Comanche 55, whose original source code is available. Comanche 55 source code was then modified by undoing changes known to have been made between revisions 51 and 55. The most-significant steps involved reverting changes related to the R-2 lunar potential model, the details of which were known from the previous, separate, independent reconstruction of the Apollo 10 Lunar Module software Luminary 69/2. The now-reconstructed Comanche 51 source code was verified by assembling it and checking that the assembled code had the expected known-correct memory-bank checksums. Note that page numbers in the reconstructed code match those on the Comanche 55 or Luminary 69 printouts, although the source code would likely have different page numbers in a contemporary Comanche 51 listing. Annotations that were not present in the contemporary source code have been added to the reconstructed code to justify each change relative to Comanche 55. Here's a guide to some of the Apollo documentation relevant to those annotations: MIT/IL engineering drawing 2021153D, sheet 3. Listing of the memory-bank checksums for Comanche 51. Comanche 55 (Apollo 11 CM final release) assembly listing. Reconstructed Luminary69/2 (Apollo 10 LM final release) assembly listing. Luminary 69 (Apollo 10 LM initial release) assembly listing. Colossus 249 (Apollo 9 CM final release) assembly listing. Programmed Guidance Equations for Colossus 2, Based on Comanche 55. A pseudocode representation of Comanche 55, showing change bars for differences from Comanche 45/2. Among documentation not actually referenced in the annotations, there is a short writeup about the reconstruction process in our software repository that may be helpful in understanding it from a different perspective. There's also a handy table that lists what the number of memory-words should be for each routine in Comanche 51, which could make a nice double-check; however, we've not performed that double-check ourselves. Comments expected to have been present in the original source code are prefixed with a single '#' symbol, whereas comments added later are prefixed by "##" or "###". Report any errors noted by creating an issue report at the Virtual AGC Project's GitHub repository.

040835,000002:                                                                                                  ## Copyright:   Public domain.
040836,000003:                                                                                                  ## Filename:    LUNAR_LANDMARK_SELECTION_FOR_CM.agc
040837,000004:                                                                                                  ## Purpose:     A section of Comanche revision 051.
040838,000005:                                                                                                  ##              It is part of the reconstructed source code for the
040839,000006:                                                                                                  ##              original release of the flight software for the Command
040840,000007:                                                                                                  ##              Module's (CM) Apollo Guidance Computer (AGC) for Apollo 11.
040841,000008:                                                                                                  ##              The code has been recreated from a copy of Comanche 055. It
040842,000009:                                                                                                  ##              has been adapted such that the resulting bugger words
040843,000010:                                                                                                  ##              exactly match those specified for Comanche 51 in NASA drawing
040844,000011:                                                                                                  ##              2021153D, which gives relatively high confidence that the
040845,000012:                                                                                                  ##              reconstruction is correct.
040846,000013:                                                                                                  ## Reference:   pp. 936
040847,000014:                                                                                                  ## Assembler:   yaYUL
040848,000015:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
040849,000016:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
040850,000017:                                                                                                  ## Mod history: 2019-07-30 MAS  Created from Comanche 55.
040851,000018: 

Page 936 This page (and this entire section) contains only assembler-generated messages.

End of include-file LUNAR_LANDMARK_SELECTION_FOR_CM.agc.  Parent file is MAIN.agc