Assembly listing generated by yaYUL

Source Code

These source-code files are part of a reconstructed copy of Comanche 44, the initial release (though not the final mission release) of the Apollo 10 Command Module (CM) Apollo Guidance Computer (AGC) software. Subsequent releases were Comanche 45 and Comanche 45/2 (the flown release on Apollo 10). The reconstruction is believed to be exactly accurate, but in the absence of an actual Apollo-era listing of Comanche 44, some explanation of the reconstruction process is needed to insure confidence in that accuracy.

The starting point was the source code of Comanche 51 (separately previously reconstructed from an Apollo-era listing of Comanche 55, flown on Apollo 11). Comanche 51 source code was then modified by undoing changes known to have been made between revisions 44 and 51. The now-reconstructed Comanche 44 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 printout, although the source code would likely have different page numbers in a contemporary Comanche 44 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 51. Here's a guide to the Apollo documentation referenced in those annotations:

MIT/IL engineering drawing 2021153D, sheet 3. Listing of the memory-bank checksums for Comanche 44.
Comanche 55 (Apollo 11 CM final release) assembly listing.
Reconstructed Comanche 51 (Apollo 11 CM initial release) assembly listing.
Colossus 249 (Apollo 9 CM final release) assembly listing.
Guidance System Operations Plan for Colossus 3, Section 5, p. xiii. Table listing some Program Request Changes (PCRs) incorporated between Comanche 45/2 and Comanche 55.
Guidance System Operations Plan for Colossus 2E, Section 3, pp. ix-x. Tables listing some Program Change Requests (PCRs) incorporated between Comanche 44 and Comanche 55.
Programmed Guidance Equations for Colossus 2, Based on Comanche 55. Provides a pseudocode representation of portions of Comanche 55, showing change bars. The software revisions from which and to which the changes occurred are indicated by the markings next to the document page number:
- "Rev. 0" pages: change bars are from Colossus 249 to Comanche 45
- "Rev. 1" pages: change bars are from Comanche 45 to Comanche 45/2
- "Rev. 2" pages: change bars are from Comanche 45/2 to Comanche 55

In most cases, only the titles (rather than the full texts) of PCRs are known. In addition to the explanatory annotations, there is also a step-by-step commentary about the reconstruction process.

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.

051848,000002:                                                                                                  ## Copyright:   Public domain.
051849,000003:                                                                                                  ## Filename:    INTERPRETIVE_CONSTANTS.agc
051850,000004:                                                                                                  ## Purpose:     A section of Comanche revision 044.
051851,000005:                                                                                                  ##              It is part of the reconstructed source code for the
051852,000006:                                                                                                  ##              original release of the flight software for the Command
051853,000007:                                                                                                  ##              Module's (CM) Apollo Guidance Computer (AGC) for Apollo 10.
051854,000008:                                                                                                  ##              The code has been recreated from a copy of Comanche 055. It
051855,000009:                                                                                                  ##              has been adapted such that the resulting bugger words
051856,000010:                                                                                                  ##              exactly match those specified for Comanche 44 in NASA drawing
051857,000011:                                                                                                  ##              2021153D, which gives relatively high confidence that the
051858,000012:                                                                                                  ##              reconstruction is correct.
051859,000013:                                                                                                  ## Assembler:   yaYUL
051860,000014:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
051861,000015:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
051862,000016:                                                                                                  ## Mod history: 2020-12-03 MAS  Created from Comanche 51.
051863,000017:

Page 1205

051865,000019: 26,2000                                           SETLOC   INTPRET1                              
051866,000020: 26,2000                                           BANK                                           
051867,000021: 
051868,000022: 26,3324                                           COUNT    23/ICONS                              
051869,000023: 
051870,000024: 26,3324           10000 00000  DP1/4TH            2DEC     .25                                   
051871,000025: 
051872,000026: 26,3326           00000 00000  UNITZ              2DEC     0          B-28                       
051873,000027: 
051874,000028: 26,3330           00000 00000  UNITY              2DEC     0          B-28                       
051875,000029: 
051876,000030: 26,3332           20000 00000  UNITX              2DEC     .5                                    
051877,000031: 
051878,000032: 26,3334           00000 00000  ZEROVECS           2DEC     0          B-28                       
051879,000033: 
051880,000034: 26,3336           00000 00000                     2DEC     0          B-28                       
051881,000035: 
051882,000036: 26,3340           00000 00000                     2DEC     0          B-28                       
051883,000037: 
051884,000038: 26,3342  26,3332               DPHALF             =        UNITX                                 
051885,000039: 26,3342           37777        DPPOSMAX           OCT      37777                                 
051886,000040: 26,3343           37777                           OCT      37777                                 
051887,000041:

Page 1206

051889,000043:                                                                                                  #  INTERPRETIVE CONSTANTS IN THE OTHER HALF-MEMORY
051890,000044: 
051891,000045: 04,2000                                           SETLOC   INTPRET2                              
051892,000046: 04,2000                                           BANK                                           
051893,000047: 
051894,000048: 04,3554                                           COUNT    14/ICONS                              
051895,000049: 
051896,000050: 04,3554           00000 00000  ZUNIT              2DEC     0          B-28                       
051897,000051: 
051898,000052: 04,3556           00000 00000  YUNIT              2DEC     0          B-28                       
051899,000053: 
051900,000054: 04,3560           20000 00000  XUNIT              2DEC     .5                                    
051901,000055: 
051902,000056: 04,3562           00000 00000  ZEROVEC            2DEC     0          B-28                       
051903,000057: 
051904,000058: 04,3564           00000 00000                     2DEC     0          B-28                       
051905,000059: 
051906,000060: 04,3566           00000 00000                     2DEC     0          B-28                       
051907,000061: 
051908,000062: 04,3570           77777                           OCT      77777                                 #  -0, -6, -12 MUST REMAIN IN THIS ORDER
051909,000063: 04,3571           77771        DEC-6              DEC      -6         B-14                       
051910,000064: 04,3572           77763        DEC-12             DEC      -12        B-14                       
051911,000065: 04,3573           37777 37777  LODPMAX            2OCT     3777737777                            #  THESE TWO CONSTANTS MUST REMAIN
051912,000066: 
051913,000067: 04,3575           37777 37777  LODPMAX1           2OCT     3777737777                            #  ADJACENT AND THE SAME FOR INTEGRATION
051914,000068: 
051915,000069: 04,3577  04,3562               ZERODP             =        ZEROVEC                               
051916,000070: 04,3577  04,3560               HALFDP             =        XUNIT                                 
051917,000071: 
051918,000072: 
051919,000073: 
051920,000074: 

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