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    {
    Hello All!

    Here's a little procedure that just poped into mind.  It's a good way to
    prevent unathorized usage of a certain task.

    { ------- CUT HERE ------- }

    Program LockItUp;

    Const
       Lock = $1234;

    Procedure Lockup(Key: Word); Assembler;
    ASM
          MOV  CX, Key
          SUB  CX, Lock
    @@1:  INC  CX
          LOOP @@1
    End;

    Begin
       Lockup($1234);
       WriteLn('Key works!');
    End.

    { ------- CUT HERE ------- }

    You could give someone a registration code who's CRC value will result in the
    same value as your Lock and if an incorrect value is entered, their system will
    lock up (at least that task will).

    Try running the program with Lockup($1235) and see what happens.  (Make sure
    you don't have anything important in memory!)

    Just an idea..

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