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Unprotect for Jumpman. by Independent (IND)

78 of 565 files independent
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First, make a copy of the master disk using DOS DISKCOPY program.
Put the original away in a safe place (i.e. under a telephone about to ring).

Load DEBUG from your DOS diskette (A>DEBUG)
Put the copy of the JUMPMAN disk in drive A:
From the DEBUG prompt (-), type the following:
 (a)  -L 0 0 0 2                  {loads first 2 sectors from Drive A:,
                                   Track 0, starting with Sector 0}

 (b)  -U 236                      {disassemble some code}
      You should see something like:
     2488:0236 B80804        MOV     AX,0408
     2488:0239 BB0000        MOV     BX,0000
     2488:023C B90127        MOV     CX,2701
     2488:023F BA0001        MOV     DX,0100
     2488:0242 CD13          INT     13
     2488:0244 7207          JB      024D  <----make sure this sucker matches
     2488:0246 B80000        MOV     AX,0000
     2488:0249 CD13          INT     13
     2488:024B EBF9          JMP     0246

If the lines match between this and your disk, you're in luck.

 (c)  -E 0244 EB 07                {tell the program to ignore a few things}

 (d)  -W 0 0 0 2                   {save the change}

 (e)  -Q                           {exit DEBUG}

Your disk is now unprotected.  Enjoy!

For those of you interested, listed below is an explanation of what you've
just done.

2488:0236 B80804        MOV     AX,0408   {verify 8 sectors}
2488:0239 BB0000        MOV     BX,0000   {doesn't do anything}
2488:023C B90127        MOV     CX,2701   {track #27 (39 decimal), sector 1}
2488:023F BA0001        MOV     DX,0100   {drive A:, side 1}
2488:0242 CD13          INT     13        {executes the verify command}
2488:0244 7207          JB      024D      {on error, continue with the pgm}
2488:0246 B80000        MOV     AX,0000   {if no error, reset the drive....
2488:0249 CD13          INT     13         execute reset, and...
2488:024B EBF9          JMP     0246       begin infinite loop to 0246}

Track 39 (decimal) on the disk has a screwy format - instruction #023C above
tries to find sector #1 on track 39.  There is no sector #1, so on the
master disk, it generates an error which is picked up by line 0244. If you've
made a DISKCOPY of the disk, the copy would have a sector #1, generate no
error, and continue on to the infinite loop.  What the change does is tell
the program to continue whether or not the error occurs.  The changed line
now reads:

2488:0244 EB07          JMP     024D  {no matter what, jump to the pgm}

Jeff Johnson 2/7/87