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    var
      s1, s2: string;
      position: byte;

    function StrPos( var str1, str2: string ): byte; assembler;
      { returns position of the first occurrence of str1 in str2 }
      { return value in AL }
      { str1 - string to search for }
      { str2 - string to search in  }
    asm
            CLD              { string operations forward                 }
            LES   DI,Str2    { load in ES:DI pointer to str2             }
            XOR   CH,CH      { clear CH                                  }
            MOV   CL,[DI]    { length str2 --> CL                        }
            AND   CL,CL      { length str2 = 0?                          }
            JZ    @Negatief  { length str2 = 0, nothing to search in     }
            MOV   BH,CL      { length str2 --> BH                        }
            INC   DI         { make DI point to the 1st char of str2     }
            LDS   SI,Str1    { load in DS:SI pointer to str1             }
            LODSB            { load in AL length str1                    }
            AND   AL,AL      { length str1 = 0?                          }
            JZ    @Negatief  { length str1 = 0, nothing to search for    }
            DEC   AL         { 1st char need not be compared again       }
            SUB   CL,AL      { length str2 - length str1                 }
            JBE   @Negatief  { length str2 < length str1                 }
            MOV   AH,AL      { length str1 --> AH                        }
            LODSB            { load in AL 1st character of str1          }
    @Start:
      REPNE SCASB            { scan for next occurrence 1st char in str2 }
            JNE   @Negatief  { no success                                }
            MOV   DX,SI      { pointer to 2nd char in str1 --> DX        }
            MOV   BL,CL      { number of chars in str2 to go --> BL      }
            MOV   CL,AH      { length str1 --> CL                        }
       REPE CMPSB            { compare until characters don't match      }
            JE    @Positief  { full match                                }
            SUB   SI,DX      { current SI - prev. SI = # of chars moved  }
            SUB   DI,SI      { current DI - # of chars moved = prev. DI  }
            MOV   SI,DX      { restore pointer to 2nd char in str1       }
            MOV   CL,BL      { number of chars in str2 to go --> BL      }
            JMP   @Start     { scan for next occurrence 1st char in str2 }
    @Negatief:
            XOR   AX,AX      { str1 is not in str2, result 0             }
            JMP   @Exit
    @Positief:
            ADD   BL,AH      { number of chars in str2 left              }
            MOV   AL,BH      { length str2 --> AX                        }
            SUB   AL,BL      { start position of str1 in str2            }
    @Exit:                   { we are finished. }
    end  { StrPos };

    begin
      s1 := ParamStr( 1 );
      s2 := ParamStr( 2 );
      writeln( StrPos( s1, s2 ) );
    end.

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