Ошибка несоответствия типов

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Grids, Menus, StdCtrls, Buttons;
 
 
 
type
  TForm1 = class(TForm)
    stringgrid2: TStringGrid;
    stringgrid3: TStringGrid;
    btn1: TBitBtn;
    mm1: TMainMenu;
    N1: TMenuItem;
    N221: TMenuItem;
    N331: TMenuItem;
    N441: TMenuItem;
    procedure N221Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure N441Click(Sender: TObject);
    procedure btn1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
  n: integer;
  a: array[1..9,1..9] of integer;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.N221Click(Sender: TObject);
begin
n:=2;
stringgrid2.RowCount:=2;
stringgrid2.ColCount:=2;
 
stringgrid3.RowCount:=2;
stringgrid3.ColCount:=2;
end;
 
procedure TForm1.FormCreate(Sender: TObject);
begin
n:=3;
stringgrid2.RowCount:=3;
stringgrid2.ColCount:=3;
 
stringgrid3.RowCount:=3;
stringgrid3.ColCount:=3;
end;
 
procedure TForm1.N441Click(Sender: TObject);
begin
n:=4;
stringgrid2.RowCount:=4;
stringgrid2.ColCount:=4;
 
stringgrid3.RowCount:=4;
stringgrid3.ColCount:=4;
end;
 
procedure TForm1.btn1Click(Sender: TObject);
var i,j:integer;
begin
 
for i:=0 to n do
for j:=0 to n do
a[i,j]:= StrToFloat(stringgrid2.cells[i,j]);
 
 for i:=0 to n do
 for j:=0 to n do a[i,j]:=Ord(a[i,j]);
 stringgrid3.Cells[i,j]:=FloatToStr(a[i,j]);
end;
 
end.

a: array[1..9,1..9] of integer;

a: array[1..9,1..9] of Extended;

a[i,j]:=Ord(a[i,j]);

a: array[1..9,1..9] of integer;

a[i,j]:=Ord(a[i,j]);

procedure TForm1.btn1Click(Sender: TObject);
var
  i,j:integer;
  S : String;
begin
 
for i:= 0 to n - 1 do
for j:= 0 to n - 1 do begin
  S := stringgrid2.cells[j, i];
  if S = '' then begin
    ShowMessage('В ячейке не задан символ. Обработка прервана.');
    Exit;
  end;
  stringgrid3.Cells[j,i] := IntToStr( Ord(S[1]) );
end;
 
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  i, j, k : Integer;
  S1, S2 : String;
  Sg1, Sg2 : TStringGrid;
begin
  Sg1 := StringGrid1;
  Sg2 := StringGrid2;
 
  for i := 0 to Sg1.RowCount - 1 do
  for j := 0 to Sg1.ColCount - 1 do begin
    S1 := Sg1.Cells[j, i];
    S2 := '';
    for k := 1 to Length(S1) do begin
      S2 := S2 + '#' + IntToStr( Ord(S1[k]) );
    end;
    Sg2.Cells[j, i] := S2;
  end;
end;