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:
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.

021486,000002:                                                                                                  ## Copyright:   Public domain.
021487,000003:                                                                                                  ## Filename:    R31.agc
021488,000004:                                                                                                  ## Purpose:     A section of Comanche revision 051.
021489,000005:                                                                                                  ##              It is part of the reconstructed source code for the
021490,000006:                                                                                                  ##              original release of the flight software for the Command
021491,000007:                                                                                                  ##              Module's (CM) Apollo Guidance Computer (AGC) for Apollo 11.
021492,000008:                                                                                                  ##              The code has been recreated from a copy of Comanche 055. It
021493,000009:                                                                                                  ##              has been adapted such that the resulting bugger words
021494,000010:                                                                                                  ##              exactly match those specified for Comanche 51 in NASA drawing
021495,000011:                                                                                                  ##              2021153D, which gives relatively high confidence that the
021496,000012:                                                                                                  ##              reconstruction is correct.
021497,000013:                                                                                                  ## Reference:   pp. 505-510
021498,000014:                                                                                                  ## Assembler:   yaYUL
021499,000015:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
021500,000016:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
021501,000017:                                                                                                  ## Mod history: 2019-07-30 MAS  Created from Comanche 55.
021502,000018: 

Page 505

021504,000020: 34,2002                                           BANK     34                                    
021505,000021: 31,2000                                           SETLOC   R31                                   
021506,000022: 31,2000                                           BANK                                           
021507,000023: 
021508,000024: 31,2000                                           COUNT*   $$/R31                                
021509,000025: 
021510,000026: 31,2000           35057        R31CALL            CAF      PRIO3                                 
021511,000027: 31,2001           05147                           TC       FINDVAC                               
021512,000028: 31,2002  E4,1770                                  EBANK=   SUBEXIT                               
021513,000029: 31,2002           02032 62064                     2CADR    V83CALL                               
021514,000030: 
021515,000031: 31,2004           35041        DSPDELAY           CAF      1SEC                                  
021516,000032: 31,2005           04662                           TC       BANKCALL                              
021517,000033: 31,2006           01732                           CADR     DELAYJOB                              
021518,000034: 31,2007           31044                           CA       EXTVBACT                              
021519,000035: 31,2010           75004                           MASK     BIT12                                 
021520,000036: 31,2011           00006                           EXTEND                                         
021521,000037: 31,2012           12004                           BZF      DSPDELAY                              
021522,000038: 
021523,000039: 31,2013           30105        DISPN5X            CA       FLAGWRD9                              #  TEST R31FLAG (IN SUNDANCE R31FLAG WILL
021524,000040: 31,2014           75014                           MASK     BIT4                                  #        ALWAYS BE SET AS R34 DOES NOT EXIST)
021525,000041: 31,2015           00006                           EXTEND                                         
021526,000042: 31,2016           12021                           BZF      +3                                    
021527,000043: 31,2017           32136                           CAF      V16N54                                #  R31   USE NOUN 54
021528,000044: 31,2020           02022                           TC       +2                                    
021529,000045: 31,2021           32137                           CAF      V16N53                                #  R34   USE NOUN 53
021530,000046: 31,2022           04662                           TC       BANKCALL                              
021531,000047: 31,2023           20561                           CADR     GOMARKF                               
021532,000048: 31,2024           05625                           TC       B5OFF                                 
021533,000049: 31,2025           05625                           TC       B5OFF                                 
021534,000050: 31,2026           12013                           TCF      DISPN5X                               
021535,000051: 
021536,000052: 31,2027           06006        V83                TC       INTPRET                               
021537,000053: 31,2030           77650                           GOTO                                           
021538,000054: 31,2031           62171                                    HAVEBASE                              #  INTEG STATE VECTORS
021539,000055: 31,2032           06006        V83CALL            TC       INTPRET                               
021540,000056: 31,2033           77650                           GOTO                                           
021541,000057: 31,2034           62140                                    STATEXTP                              #  EXTRAPOLATE STATE VECTORS
021542,000058: 31,2035           52375        COMPDISP           VLOAD    VSU                                   
021543,000059: 31,2036           00001                                    RATT                                  
021544,000060: 31,2037           02327                                    RONE                                  
021545,000061: 31,2040           51406                           PUSH     ABVAL                                 #  RATT-RONE TO 0D       PD= 6
021546,000062: 31,2041           02321                           STORE    RANGE                                 #  METERS B-29
021547,000063: 31,2042           77301                           NORM     VLOAD                                 
021548,000064: 31,2043           00047                                    X1                                    #  RATT-RONE             PD= 0
021549,000065: 31,2044           77762                           VSR1                                           
021550,000066: 31,2045           53457                           VSL*     UNIT                                  
021551,000067: 31,2046           20201                                    0,1                                   
021552,000068: 31,2047           52315                           PDVL     VSU                                   #  UNIT(LOS) TO 0D       PD= 6

Page 506

021554,000070: 31,2050           00007                                    VATT                                  
021555,000071: 31,2051           02335                                    VONE                                  
021556,000072: 31,2052           77641                           DOT                                            #  (VATT-VONE).UNIT(LOS) PD= 0
021557,000073: 31,2053           77752                           SL1                                            
021558,000074: 31,2054           36323                           STCALL   RRATE                                 #  RANGE RATE M/CS B-7
021559,000075: 31,2055           47477                                    CDUTRIG                               #  TO INITIALIZE FOR *NBSM*
021560,000076: 31,2056           77624                           CALL                                           
021561,000077: 31,2057           62311                                    R34LOS                                #  NOTE.  PDL MUST = 0.
021562,000078: 31,2060           53575        R34ANG             VLOAD    UNIT                                  
021563,000079: 31,2061           02327                                    RONE                                  
021564,000080: 31,2062           77715                           PDVL                                           #  UR TO 0D              PD= 6
021565,000081: 31,2063           15333                                    THISAXIS                              #  UNITX FOR CM, UNITZ FOR LM
021566,000082: 31,2064           77214                           BON      VLOAD                                 #  CHK R31FLAG.  ON=R31 THETA, OFF=R34 PHI
021567,000083: 31,2065           04713                                    R31FLAG                               
021568,000084: 31,2066           62070                                    +2                                    #  R31-THETA
021569,000085: 31,2067           00015                                    12D                                   
021570,000086: 31,2070           77624                           CALL                                           
021571,000087: 31,2071           47646                                    *NBSM*                                
021572,000088: 31,2072           41505                           VXM      PUSH                                  #  UXORZ TO 6D           PD=12D
021573,000089: 31,2073           01736                                    REFSMMAT                              
021574,000090: 31,2074           72431                           VPROJ    VSL2                                  
021575,000091: 31,2075           00001                                    0D                                    
021576,000092: 31,2076           53445                           BVSU     UNIT                                  
021577,000093: 31,2077           00007                                    6D                                    
021578,000094: 31,2100           47315                           PDVL     VXV                                   #  UP/2 TO 12D           PD=18D
021579,000095: 31,2101           02327                                    RONE                                  
021580,000096: 31,2102           02335                                    VONE                                  
021581,000097: 31,2103           47256                           UNIT     VXV                                   
021582,000098: 31,2104           02327                                    RONE                                  
021583,000099: 31,2105           63241                           DOT      PDVL                                  #  SIGN TO 12D, UP/2 TO MPAC     PD=18D
021584,000100: 31,2106           00015                                    12D                                   
021585,000101: 31,2107           50372                           VSL1     DOT                                   #  UP.UXORZ
021586,000102: 31,2110           00007                                    6D                                    
021587,000103: 31,2111           72565                           SIGN     SL1                                   
021588,000104: 31,2112           00015                                    12D                                   
021589,000105: 31,2113           77726                           ACOS                                           
021590,000106: 31,2114           26325                           STOVL    RTHETA                                
021591,000107: 31,2115           02327                                    RONE                                  
021592,000108: 31,2116           51041                           DOT      BPL                                   
021593,000109: 31,2117           00007                                    6D                                    
021594,000110: 31,2120           62125                                    +5                                    
021595,000111: 31,2121           44345                           DLOAD    BDSU                                  #  IF UXORZ.R NEG, RTHETA = 1 - RTHETA
021596,000112: 31,2122           02325                                    RTHETA                                
021597,000113: 31,2123           15343                                    DPPOSMAX                              
021598,000114: 31,2124           02325                           STORE    RTHETA                                #  RTHETA BETWEEN 0 AND 1 REV.
021599,000115: 31,2125           77776                           EXIT                                           
021600,000116: 31,2126           35013                           CAF      BIT5                                  #  HAVE WE BEEN ANSWERED
021601,000117: 31,2127           71044                           MASK     EXTVBACT                              
021602,000118: 31,2130           00006                           EXTEND                                         
021603,000119: 31,2131           15534                           BZF      ENDEXT                                #  YES, DIE

Page 507

021605,000121: 31,2132           41044                           CS       EXTVBACT                              
021606,000122: 31,2133           75004                           MASK     BIT12                                 
021607,000123: 31,2134           27044                           ADS      EXTVBACT                              
021608,000124: 
021609,000125: 31,2135           12027                           TCF      V83                                   
021610,000126: 31,2136           04066        V16N54             VN       1654                                  
021611,000127: 31,2137           04065        V16N53             VN       1653                                  
021612,000128: 

Page 508

021614,000130:                                                                                                  #  STATEXTP DOES AN INITIAL PRECISION EXTRAPOLATION OF THE
021615,000131:                                                                                                  #  LEM STATE VECTOR TO PRESENT TIME OR TO PIPTIME IF AV G
021616,000132:                                                                                                  #  IS ON AND SAVES AS BASE VECTOR. IF AV G IS ON RN + VN
021617,000133:                                                                                                  #  ARE USED AS THE CM STATE VECTOR AND THE INITIAL R RDOT
021618,000134:                                                                                                  #  RTHETA ARE COMPUTED WITH NO FURTHER INTEGRATION. IF AV
021619,000135:                                                                                                  #  G IS OFF A PRECISION EXTRAPOLATION IS MADE OF THE CM
021620,000136:                                                                                                  #  STATE VECTOR TO PRESENT TIME AND.....
021621,000137: 
021622,000138:                                                                                                  #    THE CM + LM STATE VECTORS ARE INTEGRATED TO PRES TIME
021623,000139:                                                                                                  #    USING PRECISION OR CONIC AS SURFFLAG IS SET OR CLEAR.
021624,000140: 
021625,000141:                                                                                                  #    IF AV G IS ON THEN SUBSEQUENT PASSES WILL PROVIDE
021626,000142:                                                                                                  #      USE OF RN + VN AS CM STATE VECTOR AND THE LM STATE
021627,000143:                                                                                                  #      VECTOR WILL BE PRECISION INTEGRATED USING LEMPREC
021628,000144: 
021629,000145:                                                                                                  #    IF SURFFLAG IS SET.
021630,000146:                                                                                                  #      CM STATE VECTOR RONE VONE + LM STATE VECTOR RATT
021631,000147:                                                                                                  #      VATT ARE USED IN COMPUTING R RDOT RTHETA.
021632,000148: 
021633,000149: 
021634,000150: 31,2140           43034        STATEXTP           RTB      BOF                                   #  INITIAL INTEGRATION
021635,000151: 31,2141           45510                                    LOADTIME                              
021636,000152: 31,2142           03751                                    V37FLAG                               
021637,000153: 31,2143           62146                                    +3                                    #  AV G OFF, USE PRES TIME
021638,000154: 31,2144           77624                           CALL                                           
021639,000155: 31,2145           62273                                    GETRVN                                #       ON,  USE RN VN PIPTIME
021640,000156: 31,2146           02343                           STORE    BASETIME                              #  PRES TIME OR PIPTIME
021641,000157: 31,2147           34041                           STCALL   TDEC1                                 
021642,000158: 31,2150           27105                                    LEMPREC                               
021643,000159: 31,2151           77775                           VLOAD                                          #  BASE VECTOR, LM
021644,000160: 31,2152           00017                                    RATT1                                 
021645,000161: 31,2153           26225                           STOVL    BASEOTP                               #    POS.
021646,000162: 31,2154           00025                                    VATT1                                 
021647,000163: 31,2155           02241                           STORE    BASEOTV                               #    VEL.
021648,000164: 31,2156           71214                           BON      DLOAD                                 
021649,000165: 31,2157           03711                                    V37FLAG                               
021650,000166: 31,2160           62035                                    COMPDISP                              #  COMPUTE R RDOT RTHETA FROM
021651,000167:                                                                                                  #  RONE(RN) VONE(VN) RATT+VATT(LEMPREC)
021652,000168: 31,2161           00015                                    TAT                                   
021653,000169: 31,2162           34041                           STCALL   TDEC1                                 
021654,000170: 31,2163           27071                                    CSMPREC                               
021655,000171: 31,2164           77775                           VLOAD                                          #  BASE VECTOR, CM
021656,000172: 31,2165           00017                                    RATT1                                 
021657,000173: 31,2166           26255                           STOVL    BASETHP                               #   POS.
021658,000174: 31,2167           00025                                    VATT1                                 
021659,000175: 31,2170           02263                           STORE    BASETHV                               #   VEL.
021660,000176: 31,2171           47014        HAVEBASE           BON      RTB                                   #  SUBSEQUENT INTEGRATIONS
021661,000177: 31,2172           03711                                    V37FLAG                               
021662,000178: 31,2173           62256                                    GETRVN5                               
021663,000179: 31,2174           45510                                    LOADTIME                              
021664,000180: 31,2175           34041                           STCALL   TDEC1                                 #  AV G OFF. SET INTEG. OF CM
021665,000181: 31,2176           27442                                    INTSTALL                              
021666,000182: 31,2177           43175                           VLOAD    CLEAR                                 
021667,000183: 31,2200           02255                                    BASETHP                               

Page 509

021669,000185: 31,2201           00263                                    MOONFLAG                              
021670,000186: 31,2202           25535                           STOVL    RCV                                   
021671,000187: 31,2203           02263                                    BASETHV                               
021672,000188: 31,2204           15543                           STODL    VCV                                   
021673,000189: 31,2205           02343                                    BASETIME                              
021674,000190: 31,2206           43014                           BOF      SET                                   #  GET APPROPRIATE MOONFLAG SETTING
021675,000191: 31,2207           04343                                    MOONTHIS                              
021676,000192: 31,2210           62212                                    +2                                    
021677,000193: 31,2211           00063                                    MOONFLAG                              
021678,000194: 31,2212           77614                           CLEAR                                          
021679,000195: 31,2213           01673                                    INTYPFLG                              
021680,000196: 31,2214           43014                           BON      SET                                   
021681,000197: 31,2215           04307                                    SURFFLAG                              
021682,000198: 31,2216           62220                                    +2                                    #  PREC. IF LM DOWN
021683,000199: 31,2217           01473                                    INTYPFLG                              #  CONIC IF LM NOT DOWN
021684,000200: 31,2220           35517                           STCALL   TET                                   
021685,000201: 31,2221           27135                                    INTEGRVS                              #  INTEGRATION --- AT LAST---
021686,000202: 31,2222           77775                           VLOAD                                          
021687,000203: 31,2223           00001                                    RATT                                  
021688,000204: 31,2224           26327                           STOVL    RONE                                  
021689,000205: 31,2225           00007                                    VATT                                  
021690,000206: 31,2226           16335                           STODL    VONE                                  #  GET SET FOR CONIC EXTRAP.,OTHER
021691,000207: 31,2227           00015                                    TAT                                   
021692,000208: 31,2230           45014                           BON      CALL                                  
021693,000209: 31,2231           04307                                    SURFFLAG                              
021694,000210: 31,2232           62267                                    GETRVN6                               #  LEMPREC IF LM DOWN
021695,000211: 31,2233           27442                                    INTSTALL                              #  ..CONIC IF NOT DOWN
021696,000212: 31,2234           77614                           SET                                            
021697,000213: 31,2235           01473                                    INTYPFLG                              
021698,000214: 31,2236           00041        OTHINT             STORE    TDEC1                                 #  ENTERED IF AV G ON TO INTEG LM
021699,000215: 31,2237           43175                           VLOAD    CLEAR                                 
021700,000216: 31,2240           02225                                    BASEOTP                               
021701,000217: 31,2241           00263                                    MOONFLAG                              
021702,000218: 31,2242           25535                           STOVL    RCV                                   
021703,000219: 31,2243           02241                                    BASEOTV                               
021704,000220: 31,2244           15543                           STODL    VCV                                   
021705,000221: 31,2245           02343                                    BASETIME                              
021706,000222: 31,2246           43014                           BOF      SET                                   
021707,000223: 31,2247           04343                                    MOONTHIS                              
021708,000224: 31,2250           62252                                    +2                                    
021709,000225: 31,2251           00063                                    MOONFLAG                              
021710,000226: 31,2252           35517                           STCALL   TET                                   
021711,000227: 31,2253           27135                                    INTEGRVS                              
021712,000228: 31,2254           77650                           GOTO                                           
021713,000229: 31,2255           62035                                    COMPDISP                              #  COMPUTE R RDOT RTHETA         
021714,000230: 31,2256           77624        GETRVN5            CALL                                           #  AV G ON
021715,000231: 31,2257           62273                                    GETRVN                                
021716,000232: 31,2260           45014                           BON      CALL                                  
021717,000233: 31,2261           04307                                    SURFFLAG                              
021718,000234: 31,2262           62267                                    GETRVN6                               #  LM DOWN, LMPREC

Page 510

021720,000236: 31,2263           27442                                    INTSTALL                              
021721,000237: 31,2264           52014                           CLEAR    GOTO                                  
021722,000238: 31,2265           01673                                    INTYPFLG                              
021723,000239: 31,2266           62236                                    OTHINT                                
021724,000240: 31,2267           34041        GETRVN6            STCALL   TDEC1                                 
021725,000241: 31,2270           27105                                    LEMPREC                               
021726,000242: 31,2271           77650                           GOTO                                           
021727,000243: 31,2272           62035                                    COMPDISP                              #  COMPUTE R RDOT RTHETA
021728,000244: 31,2273           77620        GETRVN             STQ                                            
021729,000245: 31,2274           00000                                    0D                                    
021730,000246: 31,2275           52175                           VLOAD    GOTO                                  #  AV G ON, RONE = RN VONE = VN
021731,000247: 31,2276           01171                                    RN                                    #   AND USE PIPTIME
021732,000248: 31,2277           62300                                    +1                                    
021733,000249: 31,2300           36327                           STCALL   RONE                                  
021734,000250: 31,2301           62302                                    +1                                    
021735,000251: 31,2302           52175                           VLOAD    GOTO                                  
021736,000252: 31,2303           01177                                    VN                                    
021737,000253: 31,2304           62305                                    +1                                    
021738,000254: 31,2305           16335                           STODL    VONE                                  
021739,000255: 31,2306           01205                                    PIPTIME                               
021740,000256: 31,2307           77650                           GOTO                                           
021741,000257: 31,2310           00000                                    0D                                    
021742,000258: 31,2000                                           SETLOC   R34                                   
021743,000259: 31,2000                                           BANK                                           
021744,000260: 31,2311           77776        R34LOS             EXIT                                           
021745,000261: 31,2312           30036                           CA       CDUS                                  
021746,000262: 31,2313           50120                           INDEX    FIXLOC                                
021747,000263: 31,2314           54011                           TS       9D                                    
021748,000264: 31,2315           30035                           CA       CDUT                                  
021749,000265: 31,2316           50120                           INDEX    FIXLOC                                
021750,000266: 31,2317           54013                           TS       11D                                   
021751,000267: 31,2320           30120                           CA       FIXLOC                                
021752,000268: 31,2321           66211                           AD       SIX                                   
021753,000269: 31,2322           40000                           COM                                            
021754,000270: 31,2323           50120                           INDEX    FIXLOC                                
021755,000271: 31,2324           54046                           TS       X1                                    
021756,000272: 31,2325           06006                           TC       INTPRET                               
021757,000273: 31,2326           77624                           CALL                                           
021758,000274: 31,2327           46000                                    SXTNB                                 
021759,000275: 31,2330           34015                           STCALL   12D                                   
021760,000276: 31,2331           62060                                    R34ANG                                

End of include-file R31.agc.  Parent file is MAIN.agc