TAdderMachine pascal object for adding numbers

program AdderMachineProject;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes
  { you can add units after this };

type
  TAdderMachine = object
    Numbers: array of double;
    procedure Add(num: double);
    function Sum():double;
  end;

  procedure TAdderMachine.Add(num: double);
  begin
    SetLength(Numbers, Length(Numbers) + 1);
    Numbers[Length(Numbers) - 1] := num;
  end;

  function TAdderMachine.Sum():double;
  var
    thenumber: double;
  begin
    for thenumber in Numbers do
      Result:=(Result+thenumber);
  end;

var
  inp: double;
  MyCashRegister: TAdderMachine;

begin
  WriteLn('Keep entering numbers. Enter 0 (zero) to get the sum.');
  WriteLn(StringOfChar('-', 50));
  ReadLn(inp); // get the first input

  while (inp <> 0) do begin
    MyCashRegister.Add(inp);
    ReadLn(inp);
  end;

  WriteLn(StringOfChar('-', 50));
  WriteLn(MyCashRegister.Sum():0:2);
  ReadLn;
end.