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Cracking 101, 4. by Cracking 101 (C101)

13 of 878 files magazine
Lesson 4 - Removing Doc Check for Star Control.
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                          CRACKING 101 - 1990 Edition

                                    Lesson 4
                                   revision 1

                  ┌─────────────────────────────────────────┐
                  │ REMOVING THE DOC CHECK FOR STAR CONTROL │
                  └─────────────────────────────────────────┘

         <

          Added for revision 1 -

              First, let  me  tell  you  about  a major fuckup I made.
         When I first wrote this file, I  left out a major part of the
         patch.  For all of the user who got that version,  I'm  sorry
         but even I  make  mistakes  at  3:00 in the morning.  Anyway,
         just replace the original with this updated version

                                            - Buckaroo Banzai

         >

              Hey, Buckaroo Banzai .. Cracking Guru back once again to
         help you lesser crackist learn.   This time, we will be going
         over Star Control.  This is the last lesson in  the  original
         4.  From here  on  out,  I  will  simply release lessons as I
         write them.

              I want to say a few things  about some of the groups out
         there right now.  Speed isn't everything.  I really wish that
         for example when you remove a doc check, most  of  us want it
         REMOVED.  We don't  want  to have to enter your group name or
         even typing 1 letter is to much.   We  shouldn't even see the
         menu for the doc check.  Now, I don't direct  this  to all of
         you, but there  seems  to  have  been  a move from quality to
         quickness.  Let's go back to the  days  of  SPI (and INC when
         they were first getting started) and crack right.   If  there
         is a doc check, remove it, not just fake it.

              Nuff said, on with the tutorial.

              Star Control  (SC  for  here out) is a preaty good game.
         The protection on it wasn't too  hard, but if you didn't read
         enough in to it, you would just kill the title music also.

              So, how do we go about cracking SC.  Well for this one I
         opted to break out when SC asks for the code  from  the  code
         wheel.  Originaly I  did this just for the hell of it, but it
         turned out to be a luck guess and made life a lot easier.

              As usual we will be using periscope to crack SC.  I used
         PSKEY (using int 3 as the trap interrupt not int 2) to pop in
         at the input routine.  So lets  get  started.  Load up PS and
         PSKEY, then execute Star Control.  When you get  to  the  doc
         check, break out.

              Now you  should  be at the usual IRET insturction that's
         part of PSKEY.  Now comes the  tricky  part.   Since  we  are
         using a key trap to break out during the input  sequence,  we
         could be anywhere  inside  the  entire  input routine.  So in
         cases like this I suggest finding a reference point.

              So how  do you pick the reference  point.   Well,  since
         this doc check must be entered via the keyboard  you  can bet
         somewhere it will  call  INT  16h  (bios  keyboard) (although
         there are times when this is not  true, it rare).  I think we
         should go off and find that call to that interrupt.

              So we  trace (using the 'T' command) through  some  code
         and finally come apon the follow subroutine ....

         ( NOTE: all comments were added by me )


         ; This is the actual routine that is used to get a key

         2A00:09D4 55            PUSH BP
         2A00:09D5 8BEC          MOV BP,SP
         2A00:09D7 8A6606        MOV AH,[BP+06]
         2A00:09DA 8AD4          MOV DL,AH
         2A00:09DC 80E20F        AND DL,0F
         2A00:09DF CD16          INT 16      ; Call to bios.  We will
         2A00:09E1 7509          JNZ   09EC      ;  use  this  as  our
         2A00:09E3 80FA01        CMP DL,01   ; reference point
         2A00:09E6 7504          JNZ 09EC
         2A00:09E8 33C0          XOR AX,AX
         2A00:09EA EB0A          JMP 09F6
         2A00:09EC 80FA02        CMP DL,02
         2A00:09EF 7405          JZ 09F6
         2A00:09F1 0BC0          OR AX,AX
         2A00:09F3 7501          JNZ 09F6
         2A00:09F5 48            DEC AX
         2A00:09F6 5D            POP BP
         2A00:09F7 CB            RETF

              So we write down the address  of our REFERENCE point and
         get ready to procede.  Now, It's really kinda  boring to keep
         trying to trace through the entire input routine while trying
         to enter the  code  string, so what we want to do next, is to
         figure out the input routine.   A  quick  look  at  this last
         section of code shows that it only reads in a  character  but
         really does not handle it.

              So, we  exit via the RETF at 9F7 enter the next level of
         the subroutine.  Again,  if you  manual  trace  through  this
         routine (as well as the next level up) you see that it simple
         exits out rather quickly.  This is definitly not the top loop
         of the imput routine.

              So, we trace through the next level up,  and  again exit
         quickly to a  higher  level.   But  this  time,  as  we trace
         through, we find that the it loops  back on itself.  AHA, the
         outer input loop.  Here is the code to the entire input loop.
         I have marked the place where you should enter from the lower
         level.

         ( String input loop -- Outer level )

         7C00:0835 FF365220      PUSH [2052]
         7C00:0839 FF365020      PUSH [2050]
         7C00:083D 9A2802FD41    CALL 41FD:0228     ;  Entery here
         7C00:0842 888670FE      MOV [BP+FE70],AL
         7C00:0946 0AC0          OR AL,AL
         7C00:0848 7503          JNZ 084D
         7C00:084A E99200        JMP 08DF
         7C00:084D 2AE4          SUB AH,AH
         7C00:084F 2D0800        SUB AX,0008
         7C00:0852 745A          JZ 08AE
         7C00:0854 48            DEC AX
         7C00:0855 48            DEC AX
         7C00:0856 7503          JNZ 085B
         7C00:0858 E90901        JMP 0964
         7C00:085B 2D0300        SUB AX,0003
         7C00:085E 7503          JNZ 0863
         7C00:0860 E90101        JMP 0964
         7C00:0863 8A9E70FE      MOV BL,[BP+FE70]
         7C00:0867 2AFF          SUB BH,BH
         7C00:0869 F687790B57    TEST BYTE PTR [BX+0B79],57
         7C00:086E 746F          JZ 08DF
         7C00:0870 F687790B03    TEST BYTE PTR [BX+0B79],03
         7C00:0875 740C          JZ 0883
         7C00:0877 F687790B02    TEST BYTE PTR [BX+0B79],02
         7C00:087C 7405          JZ 0883
         7C00:087E 80AE70FE20    SUB BYTE PTR [BP+FE70],20
         7C00:0883 8A8670FE      MOV AL,[BP+FE70]
         7C00:0887 C49E7EFE      LES BX,[BP+FE7E]
         7C00:088B 8BB682FE      MOV SI,[BP+FE82]
         7C00:088F 26            ES:
         7C00:0890 8800          MOV [BX+SI],AL
         7C00:0892 FF8682FE      INC WORD PTR [BP+FE82]
         7C00:0896 FFB688FE      PUSH [BP+FE88]
         7C00:089A 8D8678FE      LEA AX,[BP+FE78]
         7C00:089E 50            PUSH AX
         7C00:089F 9A56049324    CALL 2493:0456
         7C00:08A4 83C404        ADD SP,+04
         7C00:08A7 0BC0          OR AX,AX
         7C00:08A9 7534          JNZ 08DF
         7C00:08AB EB27          JMP 08D4
         7C00:08AD 90            NOP
         7C00:08AE 83BE82FE00    CMP WORD PTR [BP+FE82],+00
         7C00:08B3 7404          JZ 08B9
         7C00:08B5 FF8E82FE      DEC WORD PTR [BP+FE82]
         7C00:08B9 B008          MOV AL,08
         7C00:08BB 50            PUSH AX
         7C00:08BC 9A1003443D    CALL 3D44:0310
         7C00:08C1 8D8684FE      LEA AX,[BP+FE84]
         7C00:08C5 16            PUSH SS
         7C00:08C6 50            PUSH AX
         7C00:08C7 9A6A00843D    CALL 3D84:006A
         7C00:08CC B047          MOV AL,47
         7C00:08CE 50            PUSH AX
         7C00:08CF 9A1003443D    CALL 3D44:0310
         7C00:08D4 8D8678FE      LEA AX,[BP+FE78]
         7C00:08D8 16            PUSH SS
         7C00:08D9 50            PUSH AX
         7C00:08DA 9A8202C93C    CALL 3CC9:0282
         7C00:08DF 83BE8CFE00    CMP WORD PTR [BP+FE8C],+00
         7C00:08E4 7503          JNZ 08E9
         7C00:08E6 E94CFF        JMP 0835    ; <───┐
                                                   │
              as you can see, at this point it loops back  on  itself.
         This is what  tells  use  that  it's the outer loop.  Knowing
         that, we can just set a code  breakpoint  at  8E9  (the  next
         instruction after the loop) and execute the code.

              At this  point,  the SC will pause waiting  for  you  to
         enter the code key.  Use the code wheel and enter the correct
         key (after all,  it's  kinda  hard  to  crack  a game without
         having the proper codes right...)

              So, we have now exited the  input  loop  with everything
         intact (ie: the proper code was entered).  Next  step  is  to
         figure out what  happens  when  the  proper  code is entered.
         Well, since you have entered  the  proper  code,  just follow
         this routine out.  Remember back to lesson 2.   What  we want
         to do is find the call the to routine that does the doc check
         and remove it  somehow (a PROPER crack).  So since everything
         is in the right place, if we just  keep jumping over the code
         we should find our way out.

              So after jumping over many instructions, we come the the
         follow piece of code

         7C00:0B74 8BE5          MOV SP,BP
         7C00:0B76 5D            POP BP
         7C00:0B77 CB            RETF

              By now, you should know that what you are  looking at is
         the exit routine for a higher level language's (C or pascal)
         code.  So we  have  found  the  end  of the doc check.  After
         tracing through the RETF you find yourself looking down a cmp
         and a conditional jump.  Here  is  the  code  (NOTE!  I  have
         included the actual call to the doc check just for reference)

         45E2:0235 9A46010F4A    CALL 7C00:146   ; Call to Doc Check
         45E2:023A 83C404        ADD  SP,+04
         45E2:023D 0BC0          OR   AX,AX
         45E2:023F 7465          JZ   02A6

              Notice the value of the AX register.  Since  right after
         the doc check, it is acted upon, then it has some importance.
         So, now that  we know where the doc check takes place, how do
         we remove it.

              Well, We could patch it with the code

         45E2:0235 B40100        MOV  AX,0001
         45E2:0238 90            NOP
         45E2:0239 90            NOP

              This patch will work (I know,  it's  how I first patched
         the program).  But there is one small problem.   If  you  run
         the program after  adding  this patch, you will find that the
         title music doesn't play.  So,  this  is  now a good place to
         put the patch.

              So where  then.  Well, make note of the address  of  the
         call to the  doc  check.   Now,  restart the process but this
         time right after SC switches in to graphics mode, break out.

              Now, set a breakpoint at  the  address from above (in my
         case 45E2:0235).  Let SC run in to the intro.   You will find
         that although the  title  screen  comes up, the music doesn't
         kick in before the breakpoint is reached.

              No, they couldn't...they wouldn't..  well they did.  The
         music routines for  the intro are stored in the  routine  for
         the doc check.   Here  is  the  entire  doc  check.   I  have
         commented on some of the code


         ; these first few calls seem to load something from disk


         7C00:0146 55            PUSH BP
         7C00:0147 8BEC          MOV BP,SP
         7C00:0149 81EC9001      SUB SP,0190
         7C00:014D 57            PUSH DI
         7C00:014E 56            PUSH SI
         7C00:014F 8B4608        MOV AX,[BP+08]
         7C00:0152 0B4606        OR AX,[BP+06]
         7C00:0155 740E          JZ 0165
         7C00:0157 FF7608        PUSH [BP+08]
         7C00:015A FF7606        PUSH [BP+06]
         7C00:015D 9A65341E2D    CALL 2D1E:3465
         7C00:0162 83C404        ADD SP,+04
         7C00:0165 FF365220      PUSH [2052]
         7C00:0169 FF365020      PUSH [2050]
         7C00:016D 9A2802FD41    CALL 41FD:0228
         7C00:0172 0AC0          OR AL,AL
         7C00:0174 75EF          JNZ 0165
         7C00:0176 B80200        MOV AX,0002
         7C00:0179 898664FF      MOV [BP+FF64],AX
         7C00:017D 898672FF      MOV [BP+FF72],AX
         7C00:0181 2BC0          SUB AX,AX
         7C00:0183 898662FF      MOV [BP+FF62],AX
         7C00:0187 89866AFF      MOV [BP+FF6A],AX
         7C00:018B 898674FF      MOV [BP+FF74],AX
         7C00:018F B80100        MOV AX,0001
         7C00:0192 898666FF      MOV [BP+FF66],AX
         7C00:0196 89866CFF      MOV [BP+FF6C],AX
         7C00:019A 898670FF      MOV [BP+FF70],AX
         7C00:019E 898676FF      MOV [BP+FF76],AX
         7C00:01A2 B80300        MOV AX,0003
         7C00:01A5 898668FF      MOV [BP+FF68],AX
         7C00:01A9 89866EFF      MOV [BP+FF6E],AX
         7C00:01AD 898678FF      MOV [BP+FF78],AX

         ; Although I have NO IDEA what the hell is being setup
         ; here I suspect that it is the must

         7C00:01B1 C746860400    MOV WORD PTR [BP-7A],0004
         7C00:01B6 C746880100    MOV WORD PTR [BP-78],0001
         7C00:01BB C7468A0200    MOV WORD PTR [BP-76],0002
         7C00:01C0 C7468C0000    MOV WORD PTR [BP-74],0000
         7C00:01C5 C7468E0000    MOV WORD PTR [BP-72],0000
         7C00:01CA C746900500    MOV WORD PTR [BP-70],0005
         7C00:01CF C746920600    MOV WORD PTR [BP-6E],0006
         7C00:01D4 C746940700    MOV WORD PTR [BP-6C],0007
         7C00:01D9 C746960C00    MOV WORD PTR [BP-6A],000C
         7C00:01DE 894698        MOV [BP-68],AX
         7C00:01E1 C7469A0500    MOV WORD PTR [BP-66],0005
         7C00:01E6 C7469C0D00    MOV WORD PTR [BP-64],000D
         7C00:01EB C7469E0000    MOV WORD PTR [BP-62],0000
         7C00:01F0 C746A00100    MOV WORD PTR [BP-60],0001
         7C00:01F5 C746A20200    MOV WORD PTR [BP-5E],0002
         7C00:01FA C746A40800    MOV WORD PTR [BP-5C],0008
         7C00:01FF B80400        MOV AX,0004
         7C00:0202 8946A6        MOV [BP-5A],AX
         7C00:0205 8946A8        MOV [BP-58],AX
         7C00:0208 C746AA0600    MOV WORD PTR [BP-56],0006
         7C00:020D C746AC0800    MOV WORD PTR [BP-54],0008
         7C00:0212 C746AE0700    MOV WORD PTR [BP-52],0007
         7C00:0217 C746B00900    MOV WORD PTR [BP-50],0009
         7C00:021C C746B20A00    MOV WORD PTR [BP-4E],000A
         7C00:0221 8946B4        MOV [BP-4C],AX
         7C00:0224 C746B60C00    MOV WORD PTR [BP-4A],000C
         7C00:0229 C746B80300    MOV WORD PTR [BP-48],0003
         7C00:022E C746BA0B00    MOV WORD PTR [BP-46],000B
         7C00:0233 C746BC0D00    MOV WORD PTR [BP-44],000D
         7C00:0238 C746BE0B00    MOV WORD PTR [BP-42],000B
         7C00:023D C746C00500    MOV WORD PTR [BP-40],0005
         7C00:0242 C746C20100    MOV WORD PTR [BP-3E],0001
         7C00:0247 C746C40700    MOV WORD PTR [BP-3C],0007
         7C00:024C C746C60000    MOV WORD PTR [BP-3A],0000
         7C00:0251 C746C80600    MOV WORD PTR [BP-38],0006
         7C00:0256 C746CA0200    MOV WORD PTR [BP-36],0002
         7C00:025B C746CC0300    MOV WORD PTR [BP-34],0003
         7C00:0260 C746CE0800    MOV WORD PTR [BP-32],0008
         7C00:0265 C746D00900    MOV WORD PTR [BP-30],0009
         7C00:026A C746D20A00    MOV WORD PTR [BP-2E],000A
         7C00:026F C746D40B00    MOV WORD PTR [BP-2C],000B
         7C00:0274 C746D60C00    MOV WORD PTR [BP-2A],000C
         7C00:0279 C746D80A00    MOV WORD PTR [BP-28],000A
         7C00:027E C746DA0500    MOV WORD PTR [BP-26],0005
         7C00:0283 C746DC0D00    MOV WORD PTR [BP-24],000D
         7C00:0288 C746DE0800    MOV WORD PTR [BP-22],0008
         7C00:028D C746E00900    MOV WORD PTR [BP-20],0009
         7C00:0292 C746E20300    MOV WORD PTR [BP-1E],0003
         7C00:0297 C746E40B00    MOV WORD PTR [BP-1C],000B
         7C00:029C C78692FE0000  MOV WORD PTR [BP+FE92],0000
         7C00:02A2 C78694FE2B00  MOV WORD PTR [BP+FE94],002B
         7C00:02A8 C78696FE0200  MOV WORD PTR [BP+FE96],0002
         7C00:02AE C78698FE0300  MOV WORD PTR [BP+FE98],0003
         7C00:02B4 89869AFE      MOV [BP+FE9A],AX
         7C00:02B8 C7869CFE0500  MOV WORD PTR [BP+FE9C],0005
         7C00:02BE C7869EFE0600  MOV WORD PTR [BP+FE9E],0006
         7C00:02C4 C786A0FE0E00  MOV WORD PTR [BP+FEA0],000E
         7C00:02CA C786A2FE2B00  MOV WORD PTR [BP+FEA2],002B
         7C00:02D0 C786A4FE0900  MOV WORD PTR [BP+FEA4],0009
         7C00:02D6 C786A6FE0A00  MOV WORD PTR [BP+FEA6],000A
         7C00:02DC C786A8FE0B00  MOV WORD PTR [BP+FEA8],000B
         7C00:02E2 C786AAFE0C00  MOV WORD PTR [BP+FEAA],000C
         7C00:02E8 C786ACFE2B00  MOV WORD PTR [BP+FEAC],002B
         7C00:02EE C786AEFE0F00  MOV WORD PTR [BP+FEAE],000F
         7C00:02F4 C786B0FE0D00  MOV WORD PTR [BP+FEB0],000D
         7C00:02FA C786B2FE1000  MOV WORD PTR [BP+FEB2],0010
         7C00:0300 C786B4FE1100  MOV WORD PTR [BP+FEB4],0011
         7C00:0306 C786B6FE1200  MOV WORD PTR [BP+FEB6],0012
         7C00:030C C786B8FE1300  MOV WORD PTR [BP+FEB8],0013
         7C00:0312 C786BAFE1400  MOV WORD PTR [BP+FEBA],0014
         7C00:0318 C786BCFE1500  MOV WORD PTR [BP+FEBC],0015
         7C00:031E C786BEFE1600  MOV WORD PTR [BP+FEBE],0016
         7C00:0324 C786C0FE1700  MOV WORD PTR [BP+FEC0],0017
         7C00:032A C786C2FE0800  MOV WORD PTR [BP+FEC2],0008
         7C00:0330 C786C4FE1800  MOV WORD PTR [BP+FEC4],0018
         7C00:0336 C786C6FE2B00  MOV WORD PTR [BP+FEC6],002B
         7C00:033C C786C8FE1900  MOV WORD PTR [BP+FEC8],0019
         7C00:0342 C786CAFE2B00  MOV WORD PTR [BP+FECA],002B
         7C00:0348 C786CCFE1A00  MOV WORD PTR [BP+FECC],001A
         7C00:034E C786CEFE1B00  MOV WORD PTR [BP+FECE],001B
         7C00:0354 C786D0FE1C00  MOV WORD PTR [BP+FED0],001C
         7C00:035A C786D2FE1D00  MOV WORD PTR [BP+FED2],001D
         7C00:0360 C786D4FE1E00  MOV WORD PTR [BP+FED4],001E
         7C00:0366 C786D6FE1F00  MOV WORD PTR [BP+FED6],001F
         7C00:036C C786D8FE2000  MOV WORD PTR [BP+FED8],0020
         7C00:0372 C786DAFE2100  MOV WORD PTR [BP+FEDA],0021
         7C00:0378 C786DCFE0700  MOV WORD PTR [BP+FEDC],0007
         7C00:037E C786DEFE2200  MOV WORD PTR [BP+FEDE],0022
         7C00:0384 C786E0FE2300  MOV WORD PTR [BP+FEE0],0023
         7C00:038A C786E2FE2400  MOV WORD PTR [BP+FEE2],0024
         7C00:0390 C786E4FE2500  MOV WORD PTR [BP+FEE4],0025
         7C00:0396 C786E6FE2600  MOV WORD PTR [BP+FEE6],0026
         7C00:039C C786E8FE2B00  MOV WORD PTR [BP+FEE8],002B
         7C00:03A2 C786EAFE2700  MOV WORD PTR [BP+FEEA],0027
         7C00:03A8 C786ECFE2800  MOV WORD PTR [BP+FEEC],0028
         7C00:03AE C786EEFE2900  MOV WORD PTR [BP+FEEE],0029
         7C00:03B4 C786F0FE2A00  MOV WORD PTR [BP+FEF0],002A
         7C00:03BA 8D46F4        LEA AX,[BP-0C]
         7C00:03BD 50            PUSH AX
         7C00:03BE 8D867AFF      LEA AX,[BP+FF7A]
         7C00:03C2 50            PUSH AX
         7C00:03C3 8D862CFF      LEA AX,[BP+FF2C]
         7C00:03C7 50            PUSH AX
         7C00:03C8 8D8628FF      LEA AX,[BP+FF28]
         7C00:03CC 50            PUSH AX
         7C00:03CD E832FC        CALL 0002   ; Music Plays
         7C00:03D0 0BC0          OR AX,AX
         7C00:03D2 7503          JNZ 03D7
         7C00:03D4 E99B07        JMP 0B72
         7C00:03D7 FF36AA1E      PUSH [1EAA]
         7C00:03DB 9A0200443D    CALL 3D44:0002
         7C00:03E0 FF36AE1E      PUSH [1EAE]
         7C00:03E4 FF36AC1E      PUSH [1EAC]
         7C00:03E8 9A0C008D3D    CALL 3D8D:000C
         7C00:03ED B80201        MOV AX,0102
         7C00:03F0 50            PUSH AX
         7C00:03F1 9ADE02443D    CALL 3D44:02DE
         7C00:03F6 B80400        MOV AX,0004
         7C00:03F9 BA4000        MOV DX,0040
         7C00:03FC 52            PUSH DX
         7C00:03FD 50            PUSH AX
         7C00:03FE 8D868CFE      LEA AX,[BP+FE8C]
         7C00:0402 50            PUSH AX
         7C00:0403 9A7000963B    CALL 3B96:0070    ; Music plays
         7C00:0408 89868EFE      MOV [BP+FE8E],AX
         7C00:040C 899690FE      MOV [BP+FE90],DX
         7C00:0410 0BD0          OR DX,AX
         7C00:0412 7471          JZ 0485
         7C00:0414 2BC0          SUB AX,AX
         7C00:0416 898686FE      MOV [BP+FE86],AX
         7C00:041A 898684FE      MOV [BP+FE84],AX
         7C00:041E FFB690FE      PUSH [BP+FE90]
         7C00:0422 FFB68EFE      PUSH [BP+FE8E]
         7C00:0426 9A0A00F93C    CALL 3CF9:000A
         7C00:042B 898688FE      MOV [BP+FE88],AX
         7C00:042F 89968AFE      MOV [BP+FE8A],DX
         7C00:0433 833EB41E00    CMP WORD PTR [1EB4],+00
         7C00:0438 7514          JNZ 044E
         7C00:043A 8B4608        MOV AX,[BP+08]
         7C00:043D 0B4606        OR AX,[BP+06]
         7C00:0440 740C          JZ 044E
         7C00:0442 B80100        MOV AX,0001
         7C00:0445 50            PUSH AX
         7C00:0446 9AF4019324    CALL 2493:01F4
         7C00:044B 83C402        ADD SP,+02
         7C00:044E 2AC0          SUB AL,AL
         7C00:0450 50            PUSH AX
         7C00:0451 9A4803443D    CALL 3D44:0348
         7C00:0456 9A57331E2D    CALL 2D1E:3357
         7C00:045B 9A9911A73B    CALL 3BA7:1199
         7C00:0460 8D8684FE      LEA AX,[BP+FE84]
         7C00:0464 16            PUSH SS
         7C00:0465 50            PUSH AX
         7C00:0466 9A04007E3D    CALL 3D7E:0004    ; Music plays
         7C00:046B FFB68AFE      PUSH [BP+FE8A]
         7C00:046F FFB688FE      PUSH [BP+FE88]
         7C00:0473 9AF001F93C    CALL 3CF9:01F0
         7C00:0478 FFB690FE      PUSH [BP+FE90]
         7C00:047C FFB68EFE      PUSH [BP+FE8E]
         7C00:0480 9A78068D3D    CALL 3D8D:0678    ; Music plays
         7C00:0485 8B4608        MOV AX,[BP+08]
         7C00:0488 0B4606        OR AX,[BP+06]
         7C00:048B 7429          JZ 04B6
         7C00:048D 833EB41E00    CMP WORD PTR [1EB4],+00
         7C00:0492 740C          JZ 04A0
         7C00:0494 B80100        MOV AX,0001
         7C00:0497 50            PUSH AX
         7C00:0498 9AF4019324    CALL 2493:01F4    ; Music Plays
         7C00:049D 83C402        ADD SP,+02
         7C00:04A0 9A8C341E2D    CALL 2D1E:348C
         7C00:04A5 FF7608        PUSH [BP+08]
         7C00:04A8 FF7606        PUSH [BP+06]
         7C00:04AB 9A2A006342    CALL 4263:002A
         7C00:04B0 50            PUSH AX
         7C00:04B1 9A54006342    CALL 4263:0054

         ; this is the start of the actual  doc check.  OH! As you can
         ; tell, I wasn't too intrested in the music routines, but
         ; thought it might be fun to track them down

         7C00:04B6 9AD0098D3D    CALL 3D8D:09D0  ; Show Doc check
                                                 ; screen
         7C00:04BB B80301        MOV AX,0103
         7C00:04BE 50            PUSH AX
         7C00:04BF 9ADE02443D    CALL 3D44:02DE
         7C00:04C4 C746F60B00    MOV WORD PTR [BP-0A],000B
         7C00:04C9 C746F87900    MOV WORD PTR [BP-08],0079
         7C00:04CE C746FA2801    MOV WORD PTR [BP-06],0128
         7C00:04D3 C746FC4500    MOV WORD PTR [BP-04],0045
         7C00:04D8 B008          MOV AL,08
         7C00:04DA 50            PUSH AX
         7C00:04DB 9A1003443D    CALL 3D44:0310
         7C00:04E0 8D867AFF      LEA AX,[BP+FF7A]
         7C00:04E4 16            PUSH SS
         7C00:04E5 50            PUSH AX
         7C00:04E6 9A36007E3D    CALL 3D7E:0036  ; Show alien's face

         7C00:04EB C746E6A000    MOV WORD PTR [BP-1A],00A0
         7C00:04F0 C746EA0100    MOV WORD PTR [BP-16],0001
         7C00:04F5 C746840300    MOV WORD PTR [BP-7C],0003
         7C00:04FA 2AC0          SUB AL,AL
         7C00:04FC 50            PUSH AX
         7C00:04FD 9A1003443D    CALL 3D44:0310
         7C00:0502 8B46F8        MOV AX,[BP-08]
         7C00:0505 050700        ADD AX,0007
         7C00:0508 8946E8        MOV [BP-18],AX
         7C00:050B FFB62EFF      PUSH [BP+FF2E]
         7C00:050F FFB62CFF      PUSH [BP+FF2C]
         7C00:0513 FFB62EFF      PUSH [BP+FF2E]
         7C00:0517 FFB62CFF      PUSH [BP+FF2C]
         7C00:051B 9AE400FC44    CALL 44FC:00E4
         7C00:0520 8BF0          MOV SI,AX
         7C00:0522 9A1201E245    CALL 45E2:0112
         7C00:0527 B90500        MOV CX,0005
         7C00:052A 8BD0          MOV DX,AX
         7C00:052C 8BC6          MOV AX,SI
         7C00:052E 8BDA          MOV BX,DX
         7C00:0530 2BD2          SUB DX,DX
         7C00:0532 F7F1          DIV CX
         7C00:0534 8BD0          MOV DX,AX
         7C00:0536 4A            DEC DX
         7C00:0537 8BC3          MOV AX,BX
         7C00:0539 8BDA          MOV BX,DX
         7C00:053B 2BD2          SUB DX,DX
         7C00:053D F7F3          DIV BX
         7C00:053F 42            INC DX
         7C00:0540 8BC2          MOV AX,DX
         7C00:0542 D1E2          SHL DX,1
         7C00:0544 D1E2          SHL DX,1
         7C00:0546 03D0          ADD DX,AX
         7C00:0548 52            PUSH DX
         7C00:0549 9A2801FC44    CALL 44FC:0128
         7C00:054E 89868EFE      MOV [BP+FE8E],AX
         7C00:0552 899690FE      MOV [BP+FE90],DX
         7C00:0556 C78672FE0000  MOV WORD PTR [BP+FE72],0000

         ; This is the start of the loop the prints out the stupid
         ; message

         7C00:055C 52            PUSH DX
         7C00:055D 50            PUSH AX
         7C00:055E 9A4602FC44    CALL 44FC:0246
         7C00:0563 8946EC        MOV [BP-14],AX
         7C00:0566 8956EE        MOV [BP-12],DX
         7C00:0569 FFB690FE      PUSH [BP+FE90]
         7C00:056D FFB68EFE      PUSH [BP+FE8E]
         7C00:0571 9AF201FC44    CALL 44FC:01F2
         7C00:0576 8946F0        MOV [BP-10],AX
         7C00:0579 8D46E6        LEA AX,[BP-1A]
         7C00:057C 16            PUSH SS
         7C00:057D 50            PUSH AX
         7C00:057E 9A8202C93C    CALL 3CC9:0282
         7C00:0583 8346E80A      ADD WORD PTR [BP-18],+0A
         7C00:0587 FFB690FE      PUSH [BP+FE90]
         7C00:058B FFB68EFE      PUSH [BP+FE8E]
         7C00:058F B80100        MOV AX,0001
         7C00:0592 50            PUSH AX
         7C00:0593 9A7E01FC44    CALL 44FC:017E
         7C00:0598 89868EFE      MOV [BP+FE8E],AX
         7C00:059C 899690FE      MOV [BP+FE90],DX
         7C00:05A0 FF8672FE      INC WORD PTR [BP+FE72]
         7C00:05A4 83BE72FE05    CMP WORD PTR [BP+FE72],+05
         7C00:05A9 7CB1          JL 055C

         ; Reads in the code to check  (I think.  Oh hell it really
         ; doesn't matter)

         7C00:05AB 9A1201E245    CALL 45E2:0112
         7C00:05B0 B90C00        MOV CX,000C
         7C00:05B3 99            CWD
         7C00:05B4 F7F9          IDIV CX
         7C00:05B6 895682        MOV [BP-7E],DX
         7C00:05B9 9A1201E245    CALL 45E2:0112
         7C00:05BE B90C00        MOV CX,000C
         7C00:05C1 99            CWD
         7C00:05C2 F7F9          IDIV CX
         7C00:05C4 8956F2        MOV [BP-0E],DX
         7C00:05C7 9A1201E245    CALL 45E2:0112
         7C00:05CC B90C00        MOV CX,000C
         7C00:05CF 99            CWD
         7C00:05D0 F7F9          IDIV CX
         7C00:05D2 8956FE        MOV [BP-02],DX
         7C00:05D5 9A1201E245    CALL 45E2:0112
         7C00:05DA B90C00        MOV CX,000C
         7C00:05DD 99            CWD
         7C00:05DE F7F9          IDIV CX
         7C00:05E0 8996F4FE      MOV [BP+FEF4],DX
         7C00:05E4 FFB62AFF      PUSH [BP+FF2A]
         7C00:05E8 FFB628FF      PUSH [BP+FF28]
         7C00:05EC FF7682        PUSH [BP-7E]
         7C00:05EF 9A2801FC44    CALL 44FC:0128
         7C00:05F4 89868EFE      MOV [BP+FE8E],AX
         7C00:05F8 899690FE      MOV [BP+FE90],DX
         7C00:05FC 52            PUSH DX
         7C00:05FD 50            PUSH AX
         7C00:05FE 8D86F6FE      LEA AX,[BP+FEF6]
         7C00:0602 16            PUSH SS
         7C00:0603 50            PUSH AX
         7C00:0604 9A9A02FC44    CALL 44FC:029A
         7C00:0609 FFB62AFF      PUSH [BP+FF2A]
         7C00:060D FFB628FF      PUSH [BP+FF28]
         7C00:0611 8B46FE        MOV AX,[BP-02]
         7C00:0614 050C00        ADD AX,000C
         7C00:0617 50            PUSH AX
         7C00:0618 9A2801FC44    CALL 44FC:0128
         7C00:061D 89868EFE      MOV [BP+FE8E],AX
         7C00:0621 899690FE      MOV [BP+FE90],DX
         7C00:0625 52            PUSH DX
         7C00:0626 50            PUSH AX
         7C00:0627 8DBEF6FE      LEA DI,[BP+FEF6]
         7C00:062B 16            PUSH SS
         7C00:062C 07            POP ES
         7C00:062D B9FFFF        MOV CX,FFFF
         7C00:0630 33C0          XOR AX,AX
         7C00:0632 F2            REPNZ
         7C00:0633 AE            SCASB
         7C00:0634 F7D1          NOT CX
         7C00:0636 49            DEC CX
         7C00:0637 8BF1          MOV SI,CX
         7C00:0639 8D82F6FE      LEA AX,[BP+SI+FEF6]
         7C00:063D 16            PUSH SS
         7C00:063E 50            PUSH AX
         7C00:063F 9A9A02FC44    CALL 44FC:029A
         7C00:0644 FFB62AFF      PUSH [BP+FF2A]
         7C00:0648 FFB628FF      PUSH [BP+FF28]
         7C00:064C 8B46F2        MOV AX,[BP-0E]
         7C00:064F 051800        ADD AX,0018
         7C00:0652 50            PUSH AX
         7C00:0653 9A2801FC44    CALL 44FC:0128
         7C00:0658 89868EFE      MOV [BP+FE8E],AX
         7C00:065C 899690FE      MOV [BP+FE90],DX
         7C00:0660 52            PUSH DX
         7C00:0661 50            PUSH AX
         7C00:0662 8DBEF6FE      LEA DI,[BP+FEF6]
         7C00:0666 16            PUSH SS
         7C00:0667 07            POP ES
         7C00:0668 B9FFFF        MOV CX,FFFF
         7C00:066B 33C0          XOR AX,AX
         7C00:066D F2            REPNZ
         7C00:066E AE            SCASB
         7C00:066F F7D1          NOT CX
         7C00:0671 49            DEC CX
         7C00:0672 8BF1          MOV SI,CX
         7C00:0674 8D82F6FE      LEA AX,[BP+SI+FEF6]
         7C00:0678 16            PUSH SS
         7C00:0679 50            PUSH AX
         7C00:067A 9A9A02FC44    CALL 44FC:029A
         7C00:067F FFB62AFF      PUSH [BP+FF2A]
         7C00:0683 FFB628FF      PUSH [BP+FF28]
         7C00:0687 8B86F4FE      MOV AX,[BP+FEF4]
         7C00:068B 052400        ADD AX,0024
         7C00:068E 50            PUSH AX
         7C00:068F 9A2801FC44    CALL 44FC:0128
         7C00:0694 89868EFE      MOV [BP+FE8E],AX
         7C00:0698 899690FE      MOV [BP+FE90],DX
         7C00:069C 52            PUSH DX
         7C00:069D 50            PUSH AX
         7C00:069E 8DBEF6FE      LEA DI,[BP+FEF6]
         7C00:06A2 16            PUSH SS
         7C00:06A3 07            POP ES
         7C00:06A4 B9FFFF        MOV CX,FFFF
         7C00:06A7 33C0          XOR AX,AX
         7C00:06A9 F2            REPNZ
         7C00:06AA AE            SCASB
         7C00:06AB F7D1          NOT CX
         7C00:06AD 49            DEC CX
         7C00:06AE 8BF1          MOV SI,CX
         7C00:06B0 8D82F6FE      LEA AX,[BP+SI+FEF6]
         7C00:06B4 16            PUSH SS
         7C00:06B5 50            PUSH AX
         7C00:06B6 9A9A02FC44    CALL 44FC:029A
         7C00:06BB C746E8B200    MOV WORD PTR [BP-18],00B2
         7C00:06C0 8D86F6FE      LEA AX,[BP+FEF6]
         7C00:06C4 8946EC        MOV [BP-14],AX
         7C00:06C7 8C56EE        MOV [BP-12],SS
         7C00:06CA 8DBEF6FE      LEA DI,[BP+FEF6]
         7C00:06CE 16            PUSH SS
         7C00:06CF 07            POP ES
         7C00:06D0 B9FFFF        MOV CX,FFFF
         7C00:06D3 33C0          XOR AX,AX
         7C00:06D5 F2            REPNZ
         7C00:06D6 AE            SCASB
         7C00:06D7 F7D1          NOT CX
         7C00:06D9 49            DEC CX
         7C00:06DA 894EF0        MOV [BP-10],CX
         7C00:06DD B084          MOV AL,84
         7C00:06DF 50            PUSH AX
         7C00:06E0 9A1003443D    CALL 3D44:0310
         7C00:06E5 8D46E6        LEA AX,[BP-1A]
         7C00:06E8 16            PUSH SS
         7C00:06E9 50            PUSH AX
         7C00:06EA 9A8202C93C    CALL 3CC9:0282  ; Displays the code
                                                 ; to check

         7C00:06EF 8346E80A      ADD WORD PTR [BP-18],+0A
         7C00:06F3 FFB62AFF      PUSH [BP+FF2A]
         7C00:06F7 FFB628FF      PUSH [BP+FF28]
         7C00:06FB B85B00        MOV AX,005B
         7C00:06FE 50            PUSH AX
         7C00:06FF 9A2801FC44    CALL 44FC:0128
         7C00:0704 89868EFE      MOV [BP+FE8E],AX
         7C00:0708 899690FE      MOV [BP+FE90],DX
         7C00:070C 52            PUSH DX
         7C00:070D 50            PUSH AX
         7C00:070E 9A4602FC44    CALL 44FC:0246
         7C00:0713 8946EC        MOV [BP-14],AX
         7C00:0716 8956EE        MOV [BP-12],DX
         7C00:0719 FFB690FE      PUSH [BP+FE90]
         7C00:071D FFB68EFE      PUSH [BP+FE8E]
         7C00:0721 9AF201FC44    CALL 44FC:01F2
         7C00:0726 8946F0        MOV [BP-10],AX
         7C00:0729 2AC0          SUB AL,AL
         7C00:072B 50            PUSH AX
         7C00:072C 9A1003443D    CALL 3D44:0310
         7C00:0731 8D46E6        LEA AX,[BP-1A]
         7C00:0734 16            PUSH SS
         7C00:0735 50            PUSH AX
         7C00:0736 9A8202C93C    CALL 3CC9:0282   ; Displays "PROPER
                                                  ; response" msg

         7C00:073B 8B86F4FE      MOV AX,[BP+FEF4]
         7C00:073F 2B46F2        SUB AX,[BP-0E]
         7C00:0742 898672FE      MOV [BP+FE72],AX
         7C00:0746 0346FE        ADD AX,[BP-02]
         7C00:0749 898676FE      MOV [BP+FE76],AX
         7C00:074D 0BC0          OR AX,AX
         7C00:074F 7D09          JGE 075A
         7C00:0751 050C00        ADD AX,000C
         7C00:0754 898676FE      MOV [BP+FE76],AX
         7C00:0758 EB0A          JMP 0764
         7C00:075A 3D0C00        CMP AX,000C
         7C00:075D 7C05          JL 0764
         7C00:075F 83AE76FE0C    SUB WORD PTR [BP+FE76],+0C
         7C00:0764 8B4682        MOV AX,[BP-7E]
         7C00:0767 038672FE      ADD AX,[BP+FE72]
         7C00:076B 898674FE      MOV [BP+FE74],AX
         7C00:076F 0BC0          OR AX,AX
         7C00:0771 7D09          JGE 077C
         7C00:0773 050C00        ADD AX,000C
         7C00:0776 898674FE      MOV [BP+FE74],AX
         7C00:077A EB0A          JMP 0786
         7C00:077C 3D0C00        CMP AX,000C
         7C00:077F 7C05          JL 0786
         7C00:0781 83AE74FE0C    SUB WORD PTR [BP+FE74],+0C
         7C00:0786 8BB6F4FE      MOV SI,[BP+FEF4]
         7C00:078A D1E6          SHL SI,1
         7C00:078C 8BB262FF      MOV SI,[BP+SI+FF62]
         7C00:0790 89B672FE      MOV [BP+FE72],SI
         7C00:0794 8B8676FE      MOV AX,[BP+FE76]
         7C00:0798 D1E0          SHL AX,1
         7C00:079A D1E0          SHL AX,1
         7C00:079C 03F0          ADD SI,AX
         7C00:079E D1E6          SHL SI,1
         7C00:07A0 8B8292FE      MOV AX,[BP+SI+FE92]
         7C00:07A4 8986F4FE      MOV [BP+FEF4],AX
         7C00:07A8 3D2B00        CMP AX,002B
         7C00:07AB 7515          JNZ 07C2
         7C00:07AD 8BB674FE      MOV SI,[BP+FE74]
         7C00:07B1 D1E6          SHL SI,1
         7C00:07B3 D1E6          SHL SI,1
         7C00:07B5 03B672FE      ADD SI,[BP+FE72]
         7C00:07B9 D1E6          SHL SI,1
         7C00:07BB 8B4286        MOV AX,[BP+SI-7A]
         7C00:07BE 8986F4FE      MOV [BP+FEF4],AX
         7C00:07C2 C78684FE7800  MOV WORD PTR [BP+FE84],0078
         7C00:07C8 B85100        MOV AX,0051
         7C00:07CB 898686FE      MOV [BP+FE86],AX
         7C00:07CF 898688FE      MOV [BP+FE88],AX
         7C00:07D3 C7868AFE0900  MOV WORD PTR [BP+FE8A],0009
         7C00:07D9 C78678FE7900  MOV WORD PTR [BP+FE78],0079
         7C00:07DF C7867AFE5900  MOV WORD PTR [BP+FE7A],0059
         7C00:07E5 C7867CFE0000  MOV WORD PTR [BP+FE7C],0000
         7C00:07EB 8D86F6FE      LEA AX,[BP+FEF6]
         7C00:07EF 89867EFE      MOV [BP+FE7E],AX
         7C00:07F3 8C9680FE      MOV [BP+FE80],SS
         7C00:07F7 C78682FE0000  MOV WORD PTR [BP+FE82],0000
         7C00:07FD FFB62AFF      PUSH [BP+FF2A]
         7C00:0801 FFB628FF      PUSH [BP+FF28]
         7C00:0805 8B86F4FE      MOV AX,[BP+FEF4]
         7C00:0809 053000        ADD AX,0030
         7C00:080C 50            PUSH AX
         7C00:080D 9A2801FC44    CALL 44FC:0128
         7C00:0812 89868EFE      MOV [BP+FE8E],AX
         7C00:0816 899690FE      MOV [BP+FE90],DX
         7C00:081A 52            PUSH DX
         7C00:081B 50            PUSH AX
         7C00:081C 8D8630FF      LEA AX,[BP+FF30]
         7C00:0820 16            PUSH SS
         7C00:0821 50            PUSH AX
         7C00:0822 9A9A02FC44    CALL 44FC:029A
         7C00:0827 B047          MOV AL,47
         7C00:0829 50            PUSH AX
         7C00:082A 9A1003443D    CALL 3D44:0310
         7C00:082F C7868CFE0000  MOV WORD PTR [BP+FE8C],0000

         ; All the code you just saw.  I have no clue what it does
         ; (hey at least I'm honest) but it wasn't important.

         ; Here is the imput outer loop

         7C00:0835 FF365220      PUSH [2052]
         7C00:0839 FF365020      PUSH [2050]
         7C00:083D 9A2802FD41    CALL 41FD:0228
         7C00:0842 888670FE      MOV [BP+FE70],AL
         7C00:0846 0AC0          OR AL,AL
         7C00:0848 7503          JNZ 084D
         7C00:084A E99200        JMP 08DF
         7C00:084D 2AE4          SUB AH,AH
         7C00:084F 2D0800        SUB AX,0008
         7C00:0852 745A          JZ 08AE
         7C00:0854 48            DEC AX
         7C00:0855 48            DEC AX
         7C00:0856 7503          JNZ 085B
         7C00:0858 E90901        JMP 0964
         7C00:085B 2D0300        SUB AX,0003
         7C00:085E 7503          JNZ 0863
         7C00:0860 E90101        JMP 0964
         7C00:0863 8A9E70FE      MOV BL,[BP+FE70]
         7C00:0867 2AFF          SUB BH,BH
         7C00:0869 F687790B57    TEST BYTE PTR [BX+0B79],57
         7C00:086E 746F          JZ 08DF
         7C00:0870 F687790B03    TEST BYTE PTR [BX+0B79],03
         7C00:0875 740C          JZ 0883
         7C00:0877 F687790B02    TEST BYTE PTR [BX+0B79],02
         7C00:087C 7405          JZ 0883
         7C00:087E 80AE70FE20    SUB BYTE PTR [BP+FE70],20
         7C00:0883 8A8670FE      MOV AL,[BP+FE70]
         7C00:0887 C49E7EFE      LES BX,[BP+FE7E]
         7C00:088B 8BB682FE      MOV SI,[BP+FE82]
         7C00:088F 26            ES:
         7C00:0890 8800          MOV [BX+SI],AL
         7C00:0892 FF8682FE      INC WORD PTR [BP+FE82]
         7C00:0896 FFB688FE      PUSH [BP+FE88]
         7C00:089A 8D8678FE      LEA AX,[BP+FE78]
         7C00:089E 50            PUSH AX
         7C00:089F 9A56049324    CALL 2493:0456
         7C00:08A4 83C404        ADD SP,+04
         7C00:08A7 0BC0          OR AX,AX
         7C00:08A9 7534          JNZ 08DF
         7C00:08AB EB27          JMP 08D4
         7C00:08AD 90            NOP
         7C00:08AE 83BE82FE00    CMP WORD PTR [BP+FE82],+00
         7C00:08B3 7404          JZ 08B9
         7C00:08B5 FF8E82FE      DEC WORD PTR [BP+FE82]
         7C00:08B9 B008          MOV AL,08
         7C00:08BB 50            PUSH AX
         7C00:08BC 9A1003443D    CALL 3D44:0310
         7C00:08C1 8D8684FE      LEA AX,[BP+FE84]
         7C00:08C5 16            PUSH SS
         7C00:08C6 50            PUSH AX
         7C00:08C7 9A6A00843D    CALL 3D84:006A
         7C00:08CC B047          MOV AL,47
         7C00:08CE 50            PUSH AX
         7C00:08CF 9A1003443D    CALL 3D44:0310
         7C00:08D4 8D8678FE      LEA AX,[BP+FE78]
         7C00:08D8 16            PUSH SS
         7C00:08D9 50            PUSH AX
         7C00:08DA 9A8202C93C    CALL 3CC9:0282
         7C00:08DF 83BE8CFE00    CMP WORD PTR [BP+FE8C],+00
         7C00:08E4 7503          JNZ 08E9
         7C00:08E6 E94CFF        JMP 0835

         ; Next comes the code that checks your entry.  If you follow
         ; it through you will see it handles not only clearing the
         ; screen and printing the "GOOD GOING" message but it also
         ; handles bad entries, etc.

         7C00:08E9 8BB682FE      MOV SI,[BP+FE82]
         7C00:08ED C682F6FE00    MOV BYTE PTR [BP+SI+FEF6],00
         7C00:08F2 8DBE30FF      LEA DI,[BP+FF30]
         7C00:08F6 8DB6F6FE      LEA SI,[BP+FEF6]
         7C00:08FA 16            PUSH SS
         7C00:08FB 07            POP ES
         7C00:08FC B9FFFF        MOV CX,FFFF
         7C00:08FF 33C0          XOR AX,AX
         7C00:0901 F2            REPNZ
         7C00:0902 AE            SCASB
         7C00:0903 F7D1          NOT CX
         7C00:0905 2BF9          SUB DI,CX
         7C00:0907 F3            REPZ
         7C00:0908 A6            CMPSB
         7C00:0909 7405          JZ 0910
         7C00:090B 1BC0          SBB AX,AX
         7C00:090D 1DFFFF        SBB AX,FFFF
         7C00:0910 3D0100        CMP AX,0001
         7C00:0913 1BC0          SBB AX,AX
         7C00:0915 F7D8          NEG AX
         7C00:0917 8986F2FE      MOV [BP+FEF2],AX
         7C00:091B 0BC0          OR AX,AX
         7C00:091D 7509          JNZ 0928
         7C00:091F 837E8401      CMP WORD PTR [BP-7C],+01
         7C00:0923 7703          JA 0928
         7C00:0925 E91C02        JMP 0B44
         7C00:0928 0BC0          OR AX,AX
         7C00:092A 7506          JNZ 0932
         7C00:092C 837E8403      CMP WORD PTR [BP-7C],+03
         7C00:0930 740A          JZ 093C
         7C00:0932 0BC0          OR AX,AX
         7C00:0934 745E          JZ 0994
         7C00:0936 837E8403      CMP WORD PTR [BP-7C],+03
         7C00:093A 7358          JNB 0994
         7C00:093C B047          MOV AL,47
         7C00:093E 50            PUSH AX
         7C00:093F 9A1003443D    CALL 3D44:0310
         7C00:0944 8D867AFF      LEA AX,[BP+FF7A]
         7C00:0948 16            PUSH SS
         7C00:0949 50            PUSH AX
         7C00:094A 9A36007E3D    CALL 3D7E:0036
         7C00:094F 83BEF2FE00    CMP WORD PTR [BP+FEF2],+00
         7C00:0954 7518          JNZ 096E
         7C00:0956 FF7680        PUSH [BP-80]
         7C00:0959 FFB67EFF      PUSH [BP+FF7E]
         7C00:095D 9A1C04F93C    CALL 3CF9:041C
         7C00:0962 EB16          JMP 097A
         7C00:0964 C7868CFE0100  MOV WORD PTR [BP+FE8C],0001
         7C00:096A E972FF        JMP 08DF
         7C00:096D 90            NOP
         7C00:096E FF7680        PUSH [BP-80]
         7C00:0971 FFB67EFF      PUSH [BP+FF7E]
         7C00:0975 9A7204F93C    CALL 3CF9:0472
         7C00:097A 89867EFF      MOV [BP+FF7E],AX
         7C00:097E 895680        MOV [BP-80],DX
         7C00:0981 B008          MOV AL,08
         7C00:0983 50            PUSH AX
         7C00:0984 9A1003443D    CALL 3D44:0310
         7C00:0989 8D867AFF      LEA AX,[BP+FF7A]
         7C00:098D 16            PUSH SS
         7C00:098E 50            PUSH AX
         7C00:098F 9A36007E3D    CALL 3D7E:0036
         7C00:0994 B047          MOV AL,47
         7C00:0996 50            PUSH AX
         7C00:0997 9A1003443D    CALL 3D44:0310
         7C00:099C 8D46F6        LEA AX,[BP-0A]
         7C00:099F 16            PUSH SS
         7C00:09A0 50            PUSH AX
         7C00:09A1 9A6A00843D    CALL 3D84:006A
         7C00:09A6 B008          MOV AL,08
         7C00:09A8 50            PUSH AX
         7C00:09A9 9A1003443D    CALL 3D44:0310
         7C00:09AE 8D8684FE      LEA AX,[BP+FE84]
         7C00:09B2 16            PUSH SS
         7C00:09B3 50            PUSH AX
         7C00:09B4 9A6A00843D    CALL 3D84:006A
         7C00:09B9 83BEF2FE00    CMP WORD PTR [BP+FEF2],+00
         7C00:09BE 7503          JNZ 09C3
         7C00:09C0 E98500        JMP 0A48
         7C00:09C3 2AC0          SUB AL,AL
         7C00:09C5 50            PUSH AX
         7C00:09C6 9A1003443D    CALL 3D44:0310
         7C00:09CB 8B46F8        MOV AX,[BP-08]
         7C00:09CE 050700        ADD AX,0007
         7C00:09D1 8946E8        MOV [BP-18],AX
         7C00:09D4 FFB62EFF      PUSH [BP+FF2E]
         7C00:09D8 FFB62CFF      PUSH [BP+FF2C]
         7C00:09DC 2BC0          SUB AX,AX
         7C00:09DE 50            PUSH AX
         7C00:09DF 9A2801FC44    CALL 44FC:0128
         7C00:09E4 89868EFE      MOV [BP+FE8E],AX
         7C00:09E8 899690FE      MOV [BP+FE90],DX
         7C00:09EC C78672FE0000  MOV WORD PTR [BP+FE72],0000
         7C00:09F2 EB04          JMP 09F8
         7C00:09F4 FF8672FE      INC WORD PTR [BP+FE72]
         7C00:09F8 83BE72FE05    CMP WORD PTR [BP+FE72],+05
         7C00:09FD 7C03          JL 0A02
         7C00:09FF E94201        JMP 0B44
         7C00:0A02 52            PUSH DX
         7C00:0A03 50            PUSH AX
         7C00:0A04 9A4602FC44    CALL 44FC:0246
         7C00:0A09 8946EC        MOV [BP-14],AX
         7C00:0A0C 8956EE        MOV [BP-12],DX
         7C00:0A0F FFB690FE      PUSH [BP+FE90]
         7C00:0A13 FFB68EFE      PUSH [BP+FE8E]
         7C00:0A17 9AF201FC44    CALL 44FC:01F2
         7C00:0A1C 8946F0        MOV [BP-10],AX
         7C00:0A1F 8D46E6        LEA AX,[BP-1A]
         7C00:0A22 16            PUSH SS
         7C00:0A23 50            PUSH AX
         7C00:0A24 9A8202C93C    CALL 3CC9:0282
         7C00:0A29 8346E80A      ADD WORD PTR [BP-18],+0A
         7C00:0A2D FFB690FE      PUSH [BP+FE90]
         7C00:0A31 FFB68EFE      PUSH [BP+FE8E]
         7C00:0A35 B80100        MOV AX,0001
         7C00:0A38 50            PUSH AX
         7C00:0A39 9A7E01FC44    CALL 44FC:017E
         7C00:0A3E 89868EFE      MOV [BP+FE8E],AX
         7C00:0A42 899690FE      MOV [BP+FE90],DX
         7C00:0A46 EBAC          JMP 09F4
         7C00:0A48 B084          MOV AL,84
         7C00:0A4A 50            PUSH AX
         7C00:0A4B 9A1003443D    CALL 3D44:0310
         7C00:0A50 C746E88C00    MOV WORD PTR [BP-18],008C
         7C00:0A55 FFB62AFF      PUSH [BP+FF2A]
         7C00:0A59 FFB628FF      PUSH [BP+FF28]
         7C00:0A5D B85C00        MOV AX,005C
         7C00:0A60 50            PUSH AX
         7C00:0A61 9A2801FC44    CALL 44FC:0128
         7C00:0A66 89868EFE      MOV [BP+FE8E],AX
         7C00:0A6A 899690FE      MOV [BP+FE90],DX
         7C00:0A6E 52            PUSH DX
         7C00:0A6F 50            PUSH AX
         7C00:0A70 9A4602FC44    CALL 44FC:0246
         7C00:0A75 8946EC        MOV [BP-14],AX
         7C00:0A78 8956EE        MOV [BP-12],DX
         7C00:0A7B FFB690FE      PUSH [BP+FE90]
         7C00:0A7F FFB68EFE      PUSH [BP+FE8E]
         7C00:0A83 9AF201FC44    CALL 44FC:01F2
         7C00:0A88 8946F0        MOV [BP-10],AX
         7C00:0A8B 8D46E6        LEA AX,[BP-1A]
         7C00:0A8E 16            PUSH SS
         7C00:0A8F 50            PUSH AX
         7C00:0A90 9A8202C93C    CALL 3CC9:0282
         7C00:0A95 2AC0          SUB AL,AL
         7C00:0A97 50            PUSH AX
         7C00:0A98 9A1003443D    CALL 3D44:0310
         7C00:0A9D 8346E80B      ADD WORD PTR [BP-18],+0B
         7C00:0AA1 FFB690FE      PUSH [BP+FE90]
         7C00:0AA5 FFB68EFE      PUSH [BP+FE8E]
         7C00:0AA9 B80100        MOV AX,0001
         7C00:0AAC 50            PUSH AX
         7C00:0AAD 9A7E01FC44    CALL 44FC:017E
         7C00:0AB2 89868EFE      MOV [BP+FE8E],AX
         7C00:0AB6 899690FE      MOV [BP+FE90],DX
         7C00:0ABA 52            PUSH DX
         7C00:0ABB 50            PUSH AX
         7C00:0ABC 9A4602FC44    CALL 44FC:0246
         7C00:0AC1 8946EC        MOV [BP-14],AX
         7C00:0AC4 8956EE        MOV [BP-12],DX
         7C00:0AC7 FFB690FE      PUSH [BP+FE90]
         7C00:0ACB FFB68EFE      PUSH [BP+FE8E]
         7C00:0ACF 9AF201FC44    CALL 44FC:01F2
         7C00:0AD4 8946F0        MOV [BP-10],AX
         7C00:0AD7 8D46E6        LEA AX,[BP-1A]
         7C00:0ADA 16            PUSH SS
         7C00:0ADB 50            PUSH AX


         ; Lot's of code Huh?


         7C00:0ADC 9A8202C93C    CALL 3CC9:0282
         7C00:0AE1 C746E8BC00    MOV WORD PTR [BP-18],00BC
         7C00:0AE6 FFB690FE      PUSH [BP+FE90]
         7C00:0AEA FFB68EFE      PUSH [BP+FE8E]
         7C00:0AEE B80100        MOV AX,0001
         7C00:0AF1 50            PUSH AX
         7C00:0AF2 9A7E01FC44    CALL 44FC:017E
         7C00:0AF7 89868EFE      MOV [BP+FE8E],AX
         7C00:0AFB 899690FE      MOV [BP+FE90],DX
         7C00:0AFF 52            PUSH DX
         7C00:0B00 50            PUSH AX
         7C00:0B01 9A4602FC44    CALL 44FC:0246
         7C00:0B06 8946EC        MOV [BP-14],AX
         7C00:0B09 8956EE        MOV [BP-12],DX
         7C00:0B0C FFB690FE      PUSH [BP+FE90]
         7C00:0B10 FFB68EFE      PUSH [BP+FE8E]
         7C00:0B14 9AF201FC44    CALL 44FC:01F2
         7C00:0B19 8946F0        MOV [BP-10],AX
         7C00:0B1C 8D46E6        LEA AX,[BP-1A]
         7C00:0B1F 16            PUSH SS
         7C00:0B20 50            PUSH AX
         7C00:0B21 9A8202C93C    CALL 3CC9:0282
         7C00:0B26 B80100        MOV AX,0001
         7C00:0B29 50            PUSH AX
         7C00:0B2A 9AF4019324    CALL 2493:01F4
         7C00:0B2F 83C402        ADD SP,+02
         7C00:0B32 B047          MOV AL,47
         7C00:0B34 50            PUSH AX
         7C00:0B35 9A1003443D    CALL 3D44:0310
         7C00:0B3A 8D46F6        LEA AX,[BP-0A]
         7C00:0B3D 16            PUSH SS
         7C00:0B3E 50            PUSH AX
         7C00:0B3F 9A6A00843D    CALL 3D84:006A
         7C00:0B44 83BEF2FE00    CMP WORD PTR [BP+FEF2],+00
         7C00:0B49 7508          JNZ 0B53
         7C00:0B4B FF4E84        DEC WORD PTR [BP-7C]
         7C00:0B4E 7403          JZ 0B53
         7C00:0B50 E9A7F9        JMP 04FA
         7C00:0B53 FF76F4        PUSH [BP-0C]
         7C00:0B56 8D867AFF      LEA AX,[BP+FF7A]
         7C00:0B5A 50            PUSH AX
         7C00:0B5B FFB62EFF      PUSH [BP+FF2E]
         7C00:0B5F FFB62CFF      PUSH [BP+FF2C]
         7C00:0B63 FFB62AFF      PUSH [BP+FF2A]
         7C00:0B67 FFB628FF      PUSH [BP+FF28]
         7C00:0B6B E88EF5        CALL 00FC
         7C00:0B6E 8B86F2FE      MOV AX,[BP+FEF2]
         7C00:0B72 5E            POP SI
         7C00:0B73 5F            POP DI

         ; Here is the exit code I was talking about

         7C00:0B74 8BE5          MOV SP,BP
         7C00:0B76 5D            POP BP
         7C00:0B77 CB            RETF
         7C00:0B78 B85A06        MOV AX,065A
         7C00:0B7B CB            RETF
         7C00:0B7C B89006        MOV AX,0690
         7C00:0B7F CB            RETF


              Ok, after looking through all of that, can  you  tell me
         where to put  the  patch.   Simple.   How  about right at the
         begining of the doc check right  after the music routines (ie
         address 7C00:04B6).  Hey yeah ... good idea.   But  how do we
         want to patch  it.   Well,  since  this  is  a  higher  level
         language, we just can't use RETF.  We must reset the stack.
              Since I hate large patches,  a  simply  decided  on  the
         follow patch

         7C00:04B6 E9BB06        JMP B74

              Ok, by jumping to 0B74, we still get the  music  but the
         actual doc check  is  not  executed.   But  there  is still a
         problem.  Remember how I said  that  AX  was tested after the
         doc check.  Well,  we  still  have  to fake the  check.   The
         easiest way, is to simply NOP the condition jmp.  Here is the
         section of code again


         45E2:0235 9A46010F4A    CALL 7C00:146   ; Call to Doc Check
         45E2:023A 83C404        ADD  SP,+04
         45E2:023D 0BC0          OR   AX,AX
         45E2:023F 7465          JZ   02A6

              If you  remember, when you enter the right code, AX will
         be set to 0001 when we exit to  45E2:023A.  If we OR 0001 and
         0001 we get 0001.  Here is the binary ...


                              0000 0000 0000 0001  ( remember OR means
                                                     if  either is bit
                          or  0000 0000 0000 0001    is 1 )
                              ───────────────────
                              0000 0000 0000 0001

              Clearly we  don't want to branch at the JZ at 45E2:023F.
         So, to finish the patch we simply NOP that jmp.

              Oh boy.. that was hard.   So  let's  test  it  out.  But
         first, a little  forsight.  We will need a unique  string  of
         bytes to search  for when making the patch.  I say we use the
         code from 7C00:04C4  to  7C00:04CE   and  from  45E2:0235  to
         45E2:023F.  Yea, write  down  the  hex  equivelent  and  then
         restart.  Again break  in right after the switch to graphics.
         Now add the  patch  (ie  A  7C00:04B6  <ENTER>,  etc.).   Now
         execute the program.

              SHIT!  It  worked,  we  are  fucking amazing.   Ok,  now
         adding the patch  permenatly.   Using  PCTOOLS  (or whatever)
         search the file STARCON.EXE for the bytes mention above
         (ie: C746F60B00C746F87900C746FA2801)      But    wait,    now
         matches...Hmmm strange.  It was there just a minute ago...but
         wait there... another file STARCON.OVL (as we  all  know .OVL
         mean OVERLAY).  Let's try searching this one.

              There we  go,  that's better (it should should up on the
         13 sector read in).  Now to add  the  patch.  Simply find the
         search bytes and  the go backwards until the first  occurance
         of the hex byte 9A.  Add the patch here.  Save it.

              Next, add  the patch to 45E2:023F.  Search for the bytes
         83C4040BC07465.  The should appear  on sector 3 (give or take
         a few sectors).  Now simply change the 2 bytes 74 65 to 90 90
         and save the sector.  Now, you are good to go.

              Well shit, this has been some hell of a textfile.   1113
         lines in all.   But  what  detail.   Ok  I  hope  you learned
         something from all of this.  And  this  end the first part of
         CRACKING 101 - the 1990 edition.  From here out all lessons (
         lesson 5 and up) will be released on their own.

              I would like the thank Phantom Phlegm for  pushing me to
         finish this shit.

              Till lesson 5 this is Buckaroo Banzai, signing off.


         OH... I can  be  reached for personal help via E-MAIL on LORD
         WOLFEN's CASTLE or TOS...
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