Q68881: Pascal Example in Programmer’s Guide Won’t Compile

Article: Q68881
Product(s): See article
Version(s): 1.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | Pascal Mouse Programming Borland Turbo | mspl13_basic
Last Modified: 11-FEB-1991

The "Making Calls from Borland Turbo Pascal Programs" sample in
Appendix E of the "Microsoft Mouse Programmer's Reference" does not
compile with Turbo Pascal versions 5.0 and 6.0.

The CpuReg data structure needs to be defined as "Registers"
variables. The semicolons need to be removed from the END lines that
immediately precede ELSE. Finally, finding the segment and offset of
the pointer of the address of the user array or subroutine (functions
9,12,20,22,23,and 24) needs to be done outside of this procedure.
Passing the first element of the array or the start point of the
subroutine into the procedure, then calling the "ofs" and "seg"
functions in the procedure doesn't seem to work. This is due to how
the variables get dereferenced when passed into a procedure.

The following example compiles in both Turbo Pascal version
6.0 and Quick Pascal version 1.00:

Procedure Mouse (Var m1, m2, m3, m4, m5 : integer );

Var
   CpuReg: Registers;

begin {mouse}

   if m1 >= 0 then
      begin
     CpuReg.AX := m1;        { Load Parameters       }
     CpuReg.BX := m2;        { into appropriate      }
     CpuReg.CX := m3;        { registers             }

     if (m1 = 9) or (m1 = 12) or (m1 = 20)
        or (m1 = 22) or (m1 = 23) or (m1 = 24) then
        begin
          CpuReg.DX  :=  m4;    {m4 = offset,         }
          CpuReg.ES  :=  m5;    { and m5 = segment    }
        end                       { of the user array }
                         { or subroutine     }

      else
      if  m1 = 16  then
       begin
         CpuReg.CX  := m2;           {Left  x coordinate }
         CpuReg.DX  := m3;           {Upper y coordinate }
         CpuReg.SI  := m4;           {Right x coordinate }
         CpuReg.DI  := m5;           {Lower y coordinate }
       end
     else
         CpuReg.DX  := m4;

     Intr($33, CpuReg);              {Call mouse driver  }
                            { at Interrupt 33H  }

     m1 := CpuReg.AX;                {Return values back }
     m2 := CpuReg.BX;                { to parameters     }
     m3 := CpuReg.CX;
     m4 := CpuReg.DX;

     if (m1 = 20) then               {special returns    }
        m2 := CpuReg.ES              { from subroutines  }
   end;
end; {mouse}